Bản tin Vật lí tháng 8/2008 (hiepkhachquay)

8/14/2019 Bn tin Vt l thng 8/2008 (hiepkhachquay)

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Trn Nghim (hiepkhachquay)

[email protected]

Kin Giang, thng 8/2008

Bn tin Vt l thng 8/2008


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hiepkhachquaythuvienvatly.infoTrang 1

M phng cho thy nhng ngi saou tin khng nng lm

M phng ca i Yoshida v s phn b cht kh xung quanh mt tin sao

c ch o bi Naoki Yoshida thuc trng i hc Nagoya, cc nh nghin cu

pht biu rng m phng ca h mang li bc tranh sng sa nht t trc n nay v lm th

no nhng thng ging nh xu trong v tr s khai pht trin thnh cc tin sao, v c th l

mt bc tin n vic gii thch lm th no cc cu trc tin ha thnh sao v thin h m

chng ta thy ngy nay.

Tht l l th v chng ta khng th nhn vo cu trc ca mt tin sao v xung

quanh ca n vo lc ngi sao chng mi ra i, nh thin vn vt l Ling Gao thuc trng

i hc Durham Anh, ngi khng c lin quan trong nghin cu ny, pht biu viphysicsworld.com.

Thi k en ti v tr

Mc d nhng cch din t ph bin ca Big Bang thng ni bu tri tr nn ngp

trn nh sng hu nhngay tc th, nhng trong thc t, nhng t nm u tin ca v tr l

khng c sao. T cc php o bc x nn v tr, chng ta bit rng cc electron v ht nhn


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bt u kt hp li thnh cc nguyn t, ch yu l hydrogen, sau khong 380.000 nm. Trong

hn 300 triu nm tip theo, cc nguyn t hydrogen ny tch li thnh nhng m my kh

khng l.

Cui cng, nhng thng ging mt nh xu trong nhng m my ny bt u hnh

thnh nn vt cht v gin n. Mc d cc kin khng thng nht khi no th vt cht bi t tr thnh mt tin sao, nhng Yoshida ni rng giai on quan trng xut hin khi

cc lc hp dn chi phi s bi t lm cn bng p sut nhit ca vt cht.

Cc m phng tin sao trc y tin on khi lng ca nhng tin sao u tin s

nng gp 500 ln khi lng Mt tri ca chng ta. y l v cc nguyn t n gin nh

hydrogen v helium vn gi nhit ca chng trong mt thi gian di, to ra p sut nhit cao.

cn bng nhng p sut ny, cc tin sao s cn cc lc hp dn cao, v do cn rt nhiu

khi lng.

Tuy nhin, i nghin cu ca Yoshida khng nh cc m phng trc y ny khng

tnh trn vn n qu trnh truyn bc x, chng phn b li nng lng trong tin sao. Bng

cch tnh c s truyn bc x trong m phng ca h, cc nh nghincu nhn thy cc tin

sao c th ch nng c 1% khi lng Mt tri ca chng ta (Science321 669).

Mt bc dng hay mt bc tin ?

Rachid Ouyed, mt nh thin vn vt l ti trng i hc Calgary, ch ra rng bn cht

ca m hnh ngha l n phic gii hn sau s hnh thnh ca tin sao, cho s phnca v tr l bt nh. Vn ny phi c xem xt nghim tc, v trong nghin cu trc

y, ngi ta chng t rng [qu trnh] m h nhn thy c xu hng tiu hy nhanh chng

ci gi lcc tin sao m h tm thy.

Tuy nhin, i ca Yoshida lc ny mun m rng m phng ca h sang nhng thi

k sau ny ca s hnh thnh sao. Trong thi tip theo, lc hp dn s p o p sut nhit

trung tm, dn n s nn li v nhit tng ln chng mt triu kelvin. Vo lc ny, cc

phn t deuterium s bt u hp nhtnhng Yoshida v i ca ng khng tm thy mt

phng php lp m phng cc phn ng ht nhn trong khng gia ba chiu.

M t y l nghin cu i ca ng, Yoshida tin on chng ta s thy mt m

phng trn vn ca s hnh thnh sao hon chnh trong vng mt thp k ti v s hnh thnh

thin h trong vng 20 nm ti.

James Dacey (physicsworld.com, 31/07/2008)


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Plasmon a nh sng laser vo thng hng v hp

Nanfang Yu (tri) v Federico Capasso ti trng i hc Harvard

Cc nh nghin cu M v Nht Bn va ngh ra mt cch n gin pht ra mt

chm nh sng gn nh song song t mt laser bn dn khng cn n cc thu knh nng n

v t tin. Thay v vy, mt mng kim loi c hoa vn c s dng hp th nh sng

phn k pht ra t laser v pht n tr li theo mt hng. i nghin cu ni k thut - da

trn cc kch thch in t tp th gi l plasmon c th ch to cc laser bn dn r hn,

nh hn v hiu qu hn.

Cc laser bn dn, pht ra nh sng khi cc electron kt hp vi cc l trng ti mt

tip gip p-n, c mt chng 40 nm qua v c th tm thy trong mi th t cc h thng

truyn thng quang hc phc tp mang li sc mnh cho Internet cho n cc b tr laser gi 5

la. Mc d cc laser bn dn rt nh (mt s kch thc vo c micromt) v c th tch

hp trong cc dng c in t, nhng vng pht x nh sng ca laser cng cng c nh bc

sng ca nh sng laser. iu ny ngha l nh sng pht ra t laser b nhiu x, thng nhiu

vo c vi chc .

V a s cc ng dng laser yu cu mt chm tia chun trc vi mt s phn k nhhn nhiu, nn nh sng laser thng c chun trc bng cch t mt thu knh cht lng

cao vi gc thu gom (hay khu ) ln ti ng ra laser. Tht khng may, iu lm cho cc

cht bn dn thm t tin v tng i cng knh. Tuy nhin, nay Nanfang Yu, Federico

Capasso v cc ng s ti trng i hc Harvard M, cng vi cc nh nghin cu ti nh

sn sut thit b quang Hamamatsu Photonics, va lm chun trc nh sng laser bng cch


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t mt mng kim loi mng, khc hoa vn, ln trn b mt pht ca mt laser bn dn

(Nature Photonics doi:10.1038/nphoton.2008.152).

Cc rnh song song

Mng kim loi c mt l l mt khe rng chng 2 m lin k vi mt lot rnh

song song rng 0.8 m, su 1,5 m v cch nhau 8,9 m. B chun trc c ch to trn

mt ca mt laser bn dn pht ra nh sng hng ngoi bc sng 9,9 m.

Hinh minh ha ca b chun trc plasmon: ci khe nm trn cng ca nh v cc rnh nm bn di khe

Mt phn ca nh sng laser truyn qua l b hp th, to ra cc plasmon mt nhng

s kch thch tp th lin quan ti s lng ln cc electron trn b mt ca mng kim loi .

Khi cc plasmon truyn qua mng, chng b tn x bi cc rnh, lm cho plasmon b chuyn

ngc tr li thnh nh sng vi cng bc sngnh laser.

Kch thc ca l v cc rnh c chn sao cho nh sng ti pht x chu s giao thoa

tng cng to nn mt chm nh sng truyn hng ra ngoi v vung gc vi mt laser.

S phn k ca laser chun trc bng plasmon l vo khong 2,4o, trong khi s phn k

ca cng laser trc khi lc vi b chun trc l khong 63o.
http://www.nature.com/nphoton/journal/vaop/ncurrent/abs/nphoton.2008.152.htmlhttp://www.nature.com/nphoton/journal/vaop/ncurrent/abs/nphoton.2008.152.htmlhttp://www.nature.com/nphoton/journal/vaop/ncurrent/abs/nphoton.2008.152.htmlhttp://www.nature.com/nphoton/journal/vaop/ncurrent/abs/nphoton.2008.152.htmlhttp://www.nature.com/nphoton/journal/vaop/ncurrent/abs/nphoton.2008.152.html


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Nhng chiu mi

Mc d b chun trc ny ch hot ng theo mt chiu, nhng Yu pht biu rn i

nghin cu hin ang lm vic trn cc thit k 2D bao gm mt l hnh trn bao quanh bi

cc vng rnh ng tm. Kt qu s b trong nhm chng ti cho thy c cu ny hot ng

rt tt: mt s phn k vi trong cc mt phng nm ngang v thng ng thu c trongmt laser thc lng t,Yu ni.

Cho n nay, i nghin cu ch to cc thu knh chun trc ca h bng hai

phng php khc nhau. Mt k thut bao gmvic lng mt lp vng 1,7 m ln trn b mt

phng ca mt laser, v sau s dng mt chm ion ct cc rnh vo trong kim loi. K

thut th hai s dng chm ion ct cc rnh vo b mt ca laser, sau trnh n vi mt

lp kim loi dy 400 nm. C hai k thut mang li s ci thin nh nhau s chun trc.

Tuy nhin, ct rnh l mt k thut t tin v tn thi gian khng thch hp cho snsut hng lot. i nghin cu hin ang xem xt pht trin cc phng php mi ch to cc

b chun trcnhiu hn mt ng vi cc k thut ch to cht bn dn thng mi.

i nghin cu tin rng thit k chun trc ca h - l i tng ca mt ng dng

ng k pht minh mt ngy no c th s dng ch to cc laser bn dn nh gn, gi

thnh thp cho cng dng trong cc b cm bin quang s dng cc chm nh sng laser

pht hin cc ha cht trong mi trng, chng hn. K thut cng c th a n cc dng

c quang in t gi thnh thp hn. Mt s phn tn rt hp ca chm laser c thlm gim

rt nhiu tnh phc tp v gi thnh ca cc h thng quang, theo li thnh vin i nghincu, Hirofumi Kan, ti Hamamatsu Photonics.

Hamish Johnston (physicsworld.com, 31/07/2008)


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Bc t ph c th dn n cng l gic phn t

Mi ni dn in cao ln u tin gia mt phn t hu c n v mt in cc kimloi c thc hin bi mt i quc t cc nh vt l. Thnh tu ny c th dn nspht trin ca cc dng c in t hc phn t vi tim nng nhanh hn v nh hn so vicc transistor v cng l gic truyn thng. a phn cc dng c in t c ch to t chmt nhm cht bn dn thng dng nht l silicon. Tuy nhin, mt s phn t hu c nhDNA dng nh c nhng tnh cht in t ging nh cc cht bn dn truyn thng v mts nh nghin cu tin rng mt s loi phn t c th c s dng ch to cc dng cin t.

nh chp nhanh t mt m phng my tnh ca tip gip phn t b ko cng

Mt thun li tim tng ca nhng dng c nh th l cc phn t cc k nh so vicc cu trc bn dn, c th gip nhng nh sn sut gi ghm nhiu mch in hn na votrong mt con chip.

Tuy nhin, thc t t ra rt kh ni cc phn t n vi mt in cc kim loi sao chocc electron c dn d dng gia hai bn. Nhng tip gip ny l cn thit cho vic ch tocc dng c thc s nh transistor v cng l gic.

Ro cn ln

Nhng n lc trc y vic ch to cc tip gip n phn t bao gm s dng cc

nhm neo nh thiol lin kt cc phn t hu c vi cc in cc kim loi nh vng. Tuynhin, lin kt kim loi- phn t to ra mt hng ro th ln gia hai u tip gip v ccelectron i n chui hm qua phn t khi mt in p c t vo gia cc in cc. iuny chc chn a n mt s dn in thp,v do hiu qu thp trong cc dng c honchnh.

Mt dn cao hn s l c th nu nh cc electron c php chuyn ng nhn pho qua tip gip kim loi-phn t - nh mi electron i vo tip gip i thng quanhiu hoc t b cn tr. Hin tng ny xy ra trong nhiu dng c ng nano carbon hay cctip xc n-nguyn t, t ti lng t dn dn ln nht c th i vi mt knhelectron c thn. Tuy nhin, hin tng ny cha bao gi t c trong cc tip gip n -

phn t trc y.Nay, Jan van Ruitenbeek thuc trng i hc Leiden H Lan cng vi cc ng s

Australia, c v Ty Ban Nha c l va gii c bi ton ny bi vic ch to cc tipgip phn t dn in cao u tin. Cng trnh ny bao gm vic lin kt cc phn t benzentrc tip vi cc in cc kim loi platinum, v i nghin cu nhn thy dn ca nhngdng c ny t ti gi tr cc i c th i vi mt knh dn electron c thn.

Ghp i trc tip


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Cc nh vt l chng t c rng c th ghp i cc in cc kim loi, trongtrng hp ca h l platinum, trc tip vi gin khung carbon ca mt phn t hu c(benzen), cho php cc electron truyn d dng hn qua lp tip gip. Tht vy, dncalp tip gip c gi tr G0, bng 2e

2/h, trong e l in tch ca electron, v h l hng sPlanck. y l dn ln nht c th i vi mt knh dn electron c thn chng7,7 x 10-5 ohm-1(Phys Rev Lett101 046801).

Cc nh nghin cu ni rng h xem benzen l im khi u cho vic ch to cctip gip phn t v h s sm nghin cu cc hp cht hu c tin tin hn. Benzen tht ltng cho cng trnh ban u v n l mth n gin c th d dng nghin cu bng cck thut nh quang ph mode dao ng, cc php o n nhiu, thay th ng v v in tonchc nng mt cc b.

i nghin cu thu c nhng kt qu ca h bng cc tip gip nt c th iukhin c hc cho php h to ra nhng tip gip kch c nguyn t ca bt k kim loi no nhit helium lng. Mt khi cc nh khoa hc xc nhn c rng tip gip l sch, thh a hi benzen qua mt ng mao dn vo nhng cu trc . H quan st cc phn t ivo tip gip bng cch o s thay i tnh cht dn in ca dng c. Tip gip sau cko cng ra n gn im t gy sao cho mt cu phn t t pht hnh thnh qua n.

Nhng nghin cu c th

Tnh cht quan trng nht ca nhng tip gip ny l dn ca chng t nht cngvo mt bc ln cao hn cc tip gip c th so snh ch to bng cc nhm neo thiol, vanRuitenbeek pht biu viphysicsworld.com. Di nhng iu kin th nghim ca chng ti,cc tip gip c th gi n nh trong mt thi gian rt lu, khi kt hp vi nhit ng lnh s dng, cho php chng ti tin hnh cc nghin cu c th.

i nghin cu hin c k hoch nghin cu cc kim loi khc ngoi platinum, mtcht t tin, dng cho cc ng dng in t hc phn t.

Ci lm cho cng trnh ny ni bt l [cc nh khoa hc] a ra mt phng php

mi gn cc phn t hu c vi cc in cc kim loi, bng cch hnh thnh mt lin kt kimloi-carbon trc tip, v t ra c sc thuyt phc rng dng c ca h c mt lin kt kim loi -phn t mnh m, l bnh lun ca Latha Venkataraman thuc trng i hc Columbiatrong mt bi bo v nghin cu ng trn tAmerican Physical Society Viewpoint. iuny cho php h vt qua ro cn chnh yu trong cc dng c gc phn t, b ni.

Belle Dme (physicsworld.com, 02/08/2008)
http://link.aps.org/abstract/PRL/v101/e046801http://link.aps.org/abstract/PRL/v101/e046801http://link.aps.org/abstract/PRL/v101/e046801http://link.aps.org/abstract/PRL/v101/e046801http://link.aps.org/abstract/PRL/v101/e046801http://link.aps.org/abstract/PRL/v101/e046801http://link.aps.org/abstract/PRL/v101/e046801


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Knh hin vi nh nhm ti th trng th gii th ba

Khi nh khoa hc ngi H Lan Antonie van Leeuwenhoek ln u tin chng minhc tim nng ca chic knh hin vi vo th k th 17, nn y khoa cha c vc-xin, thucgy t hay cht kh trng. Ba th k sau ny, nn y khoa mi tr nn chuyn mn ha hn nhiu, nhng chic knh hin vi tht thit yu i vi nhiu phn ngnh nh sinh hc t bov nghin cu bnh hc vn gi nguyn, chng c g thay i ln.

i vi cc bc s phng Ty th y c l khng l mt vn g ln, nhng cc

nc ang pht trin, cc phng th nghim chn on trong lnh vc ny phi vt ln trongvic t trang b nhng chic knh hin vi bnh thng, chng va ln va t tin.

Nay cc nh khoa hc ti Vin Cng ngh California (Caltech) va pht trin mtchic knh hin vi kch c bng mt ng penny t ti phn gii ca nhng ngi anh emln hn ca n. Hn na, cc nh nghin cu khng nh h c th ch to n vi gi ch 5bng mt ci. K s sinh hc v l nh lnh o nghin cu Changhuei Yang pht biu viphysicsworld.comrng pht minh mi ca ng c truyn cm hng t nhng floater trongmt ca chng ta.

Hnh chiu thng

Floater l nhng cm nh t bo b hng bong ra khi lp bn trong ca mt v tri

qua cht gel dng nc gi l thy dch. Chng ta thong nhn thy floater l nhng chm enhay vt xc thnh thong i vo tm nhn ca chng ta.

Thng thng, chng ta nhn thy th gii v nh sng phn x t vt hi t qua mtbi thy tinh th ln trn vng mc. Tuy nhin, chng ta nhn thy cc floater bng mt c chkhc. Nhng t bo ny nm pha sau thy tinh th ca chng ta v tch t trn vng mc, vv th chng ta ch thu c mt bn scan hay hnh chiu thng ca chng. V cc chm c v ln hn bn thn cc t bo, nn c th ca chng ta c mt chic knh hin vi t nhinchng cn thu knh no c.


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Trong m hnh Caltech ca hiu ng ny, mu vt phng to c t trc tip ln trnmt b cm bin bn dn b sung xit kim loi (CMOS), n bin i cc hnh nh quang hcthnh mt tn hiu in. Php chiu thng s dng phng php ny ln u tin c phtminh vo nm 2005 bi Dirk Lange thuc trng i hc Stanford, nhng cho n khi y phn gii khng cnh tranh ni vi cc knh hin vi thng thng. Tt nht l phn gii ckch c hng pixel, hay chng ba micron.

Yang v cc ng s vt qua gii hn ny bng cch t mt mng nhm mng lntrn b cm bin ri sau chc thng n pha trn chnh gia ca tng pixel. tng ngin ny gii hn pixelnhy vi nhng vng nm ngay bn di cc l trng thc s hnhthnh mt pixel nh hn c th bt kp phn gii ca knh hin vi thng thng. Sau ,cc nh nghin cu treo mu vt trong dch quang v cho n chy vo trong cc l.

ng dng trc mt

Vy th cc bc s s dng knh hin vi kch c b ti lm g ? i vi vic chnon hay hin th cc mu vt cha cc ng vt k sinh v m nh trng su [chic knhhin vi] ny c ng dng hu nh trc mt, theo li tin s ChrisDrakely thuc Khoa Y hcv sinh v nhit i London. Tht khng may, Drakely cnh bo, h s phng i ca knh

hin vi ch c 20 ngha l n vn khng thch hp cho vic pht hin cc k sinh trng st rt,cng vic yu cu phng i cao gp 5 ln. Yang cng nhn cn thit phi ci thin hnna phn gii nhng ni rng k hoch tip theo ca ng l ng gi mt vi b cm binln trn cng mt con chip. Nu mt dy hng nghn chic knh hin vi c th tr li d liun cng mt tip gip, th ngi s dng c th quan st mt mu vt ln nhng d dngchuyn sang kiu nhn tp trung.

Nhng chic knh hin vi nh xu ny cng c th chn vo bn di da ca bnh nhn theo di s lan rng ca ung th. Mt s dng ung th lan rng ra bi cc t bo u bu ivo dng mu, mt qu trnh gi l s di cn. Cc chip s c chn vo vng thch hp chn kha nhng t bo ny. Tuy nhin, Yang ch ra rng tng ny s rt kh thc hin,v kh quan nht th cng ngh n s vn cn ch 10 n 15 nm na.

Yang pht biu rng ng ng k mt bng pht minh v ang thng tho vinhiu cng ti ha sinh a quc gia. ng hi vng chic knh hin vi ny s sm c s dng cc nc ang pht trin, nhng ng khng mun gi vai tr ch o trongvic xc tinpht minh .



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My gia tc htTrung Quc nhm ti cc quark duyn

My d ht BES-II c thit k li ti vng va chm ca BEPC-II nng cp.

Hai mi nm sau khi n cho nhng electron v positron m vo nhau ln u tin,

c my gia tc vt l ht hng u ca Trung Quc c th s sm nng cao tc cc va chm

ca n ln thm 100 ln.

S tng cng sut ln ny s l kt qu ca mt t nng cp ko di bn nm ti my

va chm electron-positron Bc Kinh (BEPC) v thit k li my d ht ca n, ph k Bc

Kinh (BES), tiu tn ht 640 triu nhn dn t (77 triu la). Cch y hai tun, thit b qua

kim tra k lng nhn thy s tr li ca nhng va chm ht, v cc nh nghin cu hin

ang iu chnh n ti u ha thng lng va chm.

Ti ngh ngi ta ang lm vic ct lc y nhanh s nng cp, iu chnh c

my cho hiu sut cao hn v thu thp d liu cng sm cng tt, theo li Hesheng Chen,

gim c Vin Vt l Nng lng cao (IHEP), c quan iu hnh c my va chm. Chen pht

biu viphysicsworld.com rng ng ang trng i nhng s liu u tin c th s dngc t nhng va chm c tin hnh vo ma thu ti.

Cn nhiu s liu thng k hn

BEPC l mt t hp hai mc ch, cung cp c skim tra cho ngnh vt l ht ng

thi cung cp bc x synchrotron tia X cng dng cho cc nghin cu v cht liu hc v khoa

hc s sng. dng thc ban u ca n, n c mt vng nam chm n di 240 m lm gia


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tc cc chm electron v positron theo nhng hng ngc nhau, cho chng va chm nhau

vi thng lng 1031ht mi cm2mi giy (cm2s1).

Cc va chm to ra cc ht cha mt quark duyn v mt phn quark duyn, chng

nhanh chng phn hy thnh cc meson khc. S dng BES o nng lng v xung lng

ca nhng mnh v ny, cc nh nghin cu c th o c nhiu tnh cht khc nhau ca ccht duyn b m, v d nh J/ mt ht cha mt quark duyn v mt phn quark duyn.

Cc nh nghin cu cn c th o c ci gi l gi tr R cho bit cc va chm sn sinh ra

cc hadron (cc ht cha quark) thng xuyn nh th no.

My va chm nng cp, gi tn l BEPC-II, c thm mt vng nam chm na vo t

hp. iu ny ngha l cc electron v positron c th c gia tc c lp nhau, sao cho c

ti 93 chm so vi trc y ch c mt chm c th cho va vo tng vng. Thng lng

v th tng ln gp ba, nhng Chen ngh s t ti 3 x 1032 cm2s1 vo cui nm nay v

1033 cm2s1trong hai nm na, nh du mt s ci tin 100 bc. Thit k li my d ht, gitn l BES-II, s dng cc nam chm siu dn mnh hn o nng lng v xung lng ca

cc ht mnh v vi chnh xc cao hn.

Trong nm n tm nm qua, c nhng kt qu l th trong lnh vc quark duyn

cc pentaquark, v trng thi lin kt pp(bar) c trng thy BEPC, Chen gii thch.

Nhng t trc cho n gi, chng ta cha tht s hiu c cc ht ; chng ta cn c

thm s liu thng k tri cht ly chng.

C my tt nht cho cc ht tch duyn

Chen ngh rng s gia tng d liu s gip tm kim nhng s kin phn hy him. N

cng s cho cc ct sai s tt hn i vi gi tr R trong vng nng lng duyn, hin nay n

vo khong 6% nhng BEPC-II s lm n xung chng 1-2%.

Di dng cc my va chm electron-positron, BEPC-II t vo u gn vi vng

gia cc cc nng lng va chm, khong 3-5 GeV. DAFNEmt my gia tc t ti Phng

th nghim quc gia Fascati gn Rome mi y cng va nng cp cho m cc electron v

proton vo nhau khong 1 GeV to ra meson phi. nhng nng lng cao hn, cKEKB ti KEK Nht Bn v mi y l PEP-II khp kn ti SLAC M, c hai hot ng

khong 10 GeV to ra meson B. Cng c nhng phin bn cng sut cao hn ca cc

xng B va nhc ti ny ang vn ng trin khai. BEPC-II l c my tt nht trong vng

nng lng duyn, Chen ni.

Jon Cartwright (physicsworld.com, 06/08/2008)


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M phng vt cht ti cho thycc qung ho quang vn cc

Mt hnh nh ca vng m phng do Piero Madau v cc ng s thc hin

Cc nh v tr hc M v Thy S va thc hin c m phng chi tit nht t

trc n nay v cch thc cc tng tc hp dn a n cc qung vt cht ti m chngta thy gn tm ca cc thin h ngy nay. K cng c th gip cc th nghim tng lai

tm ly bn cht ca vt cht ti, mt cht hay lng trnh c cho l cu thnh gn mt phn

t ca v tr.

M phng , tin hnh trn mt thng v chy trn mt siu my tnh, v th s

tin trin ca hn mt t ht vt cht ti k t mt vi triu nm sau Big Bang. N cho thy cc

qung vt cht ti km trn hn trc nay ngi ta vn ngh.

y l tnh ton c phn gii tt nht ca qung ho quang ca Di Ngn h cthc hin t trc n nay, vi phn gii khi lng tt hn 5 n 60 ln so vi cc tnh

ton ln nht trc y, Piero Madau ti trng i hc California Santa Cruz, gii thch.

Trc y, cc vng bn trong ca qung t ra trn nhng nay chng ti c chi tit

nhn thy cc cc m c ca vt cht ti.

Cu trc quy m nh


14/50


Cc nh vt l tin rng vt cht ti cu thnh nn phn ch yu ca ton b vt cht

trong v tr, nhiu hn vt cht thng thng xp x 5 trn 1. Khng th nh thy i vi cc

knh thin vn hin i, n khng phng thch cht nh sng hay nhit no v ch tng tc

qua s hp dn. S ph bin ca n cn c ngha l vt cht ti c mt tc ng quan trng ln

s tin ha cu trc ca v tr.

Madaucng vi cc ng s ti Santa Cruz, Vin Nghin cu Cao cp, New Jersey,

v i hc Zurich tin hnh m phng ca ng s dng m hnh vt cht ti lnh c

chp nhn rng ri ca v tr. Theo m hnh ny, s hp dn ban u tc dng ln nhng

thng ging mt nh c mt khng bao lu sau Big Bang ht li cc cc vt cht ti u

tin li vi nhau. Nhng cc ny xut hin v ln thnh nhng cc ln hn na, to thnh cc

ging hp dn m vt cht bnh thng ri vo v hnh thnh nn cc sao v thin h, pht

trin thnh cc thin h trng vng trung t ca qung vt cht ti.

Mc d cc m phng trc y c s thnh cng hp l vic m t s tin ha vtr, nhng vic tm hiu bn cht ca vt cht ti sc h tr bi kin thc v cu trc quy

m nh hn ca n. t c iu ny, Madau v cc ng s phi s dng 3000 b vi x

l mc song song trong mt thng theo di cc tng tc hp dn ca 1,1 t ht vt cht ti.

M phng bt u 20 triu nm sau Big Bang v a vo khun kh 13,7 t nm tin ha, to

ra mt ci qung c kch thc bng vi kch thc qung ca Di Ngn h.

Cc kt qu ca h h l mt cu trc kiu bp b Nga, vi ton b cc th h cm vt

cht ti t tin bo v cho mt lot cu trc con n nu. M phng cho thy cc cm m c

s n np trong nhng vng bn trong ca qung ho quang (Nature457 735).

i tm bng chng

y l ln u tin mt m phng bng s c th nghin cu vt cht ti cu thnh

nn mt thin h tiu biu xung n thang khi lng ca mt nghn khi lng mt tri thay

v ch vo trm nh trc y, theo li Asantha Cooray, mt nh v tr hc ti trng i

hc California, Irvine. Vic ny tng ng vi chp mt bc nh ca mt sn vn ng

cricket v cui cng c th nhn thy tng l c mt, thay v ch cc m mu xanh.

Cc nh vt l tin rng cc ht vt cht ti, v d nh ci gi l cc ht nng tng tc

yu (WIMP), c th va chm v hy ln nhau ng thi pht ra tia gamma. Cc tia gamma ny

c th c pht hin bi cc knh thin vn t trn khng gian, trong c GLAST mi

phng ln gn y. Theo Madau v ngi ng s ca ng, Juerg Diemand, cc cm m c

hn tin on bi m phng ca h s pht ra rt nhiu tia gamma, cho php d dng pht hin

ra chng.
http://www.nature.com/nature/journal/v454/n7205/abs/nature07153.htmlhttp://www.nature.com/nature/journal/v454/n7205/abs/nature07153.htmlhttp://www.nature.com/nature/journal/v454/n7205/abs/nature07153.htmlhttp://www.nature.com/nature/journal/v454/n7205/abs/nature07153.htmlhttp://www.nature.com/nature/journal/v454/n7205/abs/nature07153.htmlhttp://www.nature.com/nature/journal/v454/n7205/abs/nature07153.htmlhttp://www.nature.com/nature/journal/v454/n7205/abs/nature07153.html


15/50


Robert Caldwell ti Dartmouth College, New Hampshire, ngh rng m phng ca i

nghin cu s gip tm hiu cc tn hiu tim nng t GLAST v cc chin lc tm kim ht

vt cht ti khc. Tht l ht sc ho hng khi trng thy bng chng thin vn vt l, ng

ni, thm: v tng tng s la chn ng lc, ht nh cc tm kim ang thc y cc gii

hn ca quan nim ca chng ta v vt cht ti!

Bob Swarup (physicsworld.com, 06/08/2008)

CERN tit lu thng 9 s vn hnh LHC

My Va chm Hadron Ln th nghim ln nht trong ngnh vt l ht s khi ngnghim chnh vo ngy 10 thng 9, theo cc vin chc ti phng th nghim chu u CERN.Cc vin chc pht biu rng vo ngy ny, cc k s s thc hin nhng n lc u tin nhmlm cho quay trn cc chm proton vng quanh my gia tc di 27 km.

Vi tt c tm phn khu ca LHC c lm lnh ti 1,9 K, chm proton u tin s c a vo theo chiu kim ng h vo cui tun ny. Php kim tra s bao gm vic ng

b ha LHC vi Siu Proton Synchrotron (SPS), giai on cui cng ca chui my bm htca my gia tc t cc chm proton cng cao c a vo vnh ai LHC.

Cc php kim tra s tip tc n u thng 9 vi cc s ng thi kim tra s bmproton theo chiu ngc chiu kim ng h.

Gi s khng c trc trc k thut no ng k, CERN ang hng ti s quay trntrn vn u tin ca cc proton vo hm 10 thng 9 khi chng s c bm vo vi nnglng 450 GeV. Mt khi vic ny c thit lp, hai chm proton s c lm cho va chmnhau, v bc cui cng ca s mnh LHC gia tc cc proton ln 5 TeV mi chm s btu.

Michael Banks (physicsworld.com, 07/08/2008)


16/50


ng nano mrng ranh gii ca in t hc

Cc nh vt l Nht Bn va tm c mt phng php phn tn cc ng nano

carbon vo mt cht lng polymer to ra mt cht liu nh cao su dn in. Cc nh pht

minh ni cht liu ca h, dn in tt hn cc cht n hi khc, l mt bc tin quan trng

hng ti hin thc ha in t hc co gin dng cho nghin cu r bt v cc dng c in

t khc.

Trc y, khi cc nh nghin cu c gng to ra cc hn hp ng nano -polymer, th

lc ni phn t mnh gia cc ng nano lun lm cho cc cu trc co cm li vi nhau, to ra

mt cht liu yu t. Tuy nhin, bng cch trn cc ng nano vi mt cht lng ion, nhm

nghin cu ngi Nht ng u l Takao Someya trng i hc Tokyo lm ch

c vic lm cho chng phn tn u n.

S dng k thut ny, cc nh nghin cu c th nh i nhiu n mt phn nm

trng lng ca polymer cho ng nano m khng lm gim tnh do c hc ca n. Cht liu

thu c cng vi s dn in ca cc ng nano c th ko cng ln ti 70% m khng bph hng (Science Express 10.1126/science.1160309).

iu ny m rng thm chn tri ng dng ca cc ng nano carbon trong mt xu

hng mi quan trng, theo li Ray Baughman ti trng i hc Texas. Khm ph bt ng

nht l vic thm ti 20% trng lng ng nano khng lm gim s bin dng n hi.


17/50


in t hc co gin

Trong khi nhiu k s tp trung n lc ca h vo vic thu nh cc dng c in t, th

hot ng theo ui in t hc co gin a cc k s n mt s thch thc hon ton khc.

Cc cht liu mong mun cn phi biu hin hiu sut in t tuyt vi ln bn vt l.

Cc n lc ban u nhm ch to in t hc co gin c xu hng hoc l gn cc linh

kin in t chun vo cao su hoc l tch hp trc tip chng vi cc mng plastic. Mc d

Someya nhn ra c mt s tin b ng k, nhng ng tin rng cc dng c b km h m

bi s lp t phi n hi.

i nghin cu ca Someya bt u ch to cht liu in t co gin ca h bng cch

trn cc ng nano vi mt cht lng ion 1-butyl-3-methylimidazolium bisimide. H cho hn

hp bt nho mu en, dy thu c vo vi mt polymer lng v phn tn n trn mt bn

thy tinh. Cui cng, h trng n vi cao su silicon v cho n sp t.

Hin nay, i nghin cu ang nh gi lc quan cc tnh cht c v in ca cc cht

dn n hi ca h. H cng ang nghin cu cc qu trnh in n kinh t mi c th cho php

cht liu thay th cc dy dn tt trong cc mch tch hp.

Song song vi vic ci tim cc cng ngh hin c, Someya hi vng cc cht dn n

hi s m ra nhng cnh ca i ti cc ng dng khp kn cho in t hc gc silicon truyn

thng v d nh da in t nhn to.



18/50


ng nano carbon, nhng khng 'nano'

nh minh ha mt ng carbon khng l

c cc ng nano carbon, fullerene v bt nano, nhng nay cc nh nghin cu va

pht hin ra mt loi cht liucarbon mi na: cc ng carbon khng l. Ln hn hng nghn

ln so vi nhng ngi anh em nano cua chng, nhng ng ny c cc tnh cht c v in

ngoi hng v c th tm thy ng dng t cc dng c vi in t cho n o gip chng n.

Trong 20 nm qua, cc nh nghin cu khm ph ra mt vi dng thc mi ca

carbon ngoi graphite (loi carbon tm thy trong bt ch) v kim cng. Cc ng carbon

khng l, pht minh bi Huisheng Peng v cc ng s ti Phng th nghim quc gia Los

Alamos M v trng i hc Fudan Trung Quc, c ng knh 40100 m v di hng

cm, khin cho chng khng ging nh cc ng nano carbon c th nhn thy i vi mt

trn. Cc nh nghin cu ch to ra chng bng mt qu trnh lng hi ha hc bao gm vicun nngmt hn hp ca ethylene v du paraffin ln ti 850oC trong mt l ng thch anh

(Physical Review Lettersang in).

Knh hin vi in t qut cho thy cc thnh ca cc ng, dy chng 1 micron, cha

cc l hnh ch nht kch thc t hng trm nano mt n hng micron. Knh hin vi in t
http://physicsworld.com/cws/article/news/35364/1/CCTshttp://physicsworld.com/cws/article/news/35364/1/CCTshttp://physicsworld.com/cws/article/news/35364/1/CCTs


19/50


truyn qua phn gii cao h l thm cc thnh c mt cu trc tinh th graphite xp lp, v

khong cch gia cc lp, xc nh bng s nhiu x tia X, l 0,34 nm bng vi graphite.

nh chp bng knh hin vi in t qut ca cc ng carbon khng l

Nh v bn

Cc ng rt nh v c khi lng ring bng vi khi lng ring ca bt nano carbon,

hoc chng 10 mg/cm3

. Ngoi ra, chng tht bn, vi sc cng ti a gn 7 Gpa, cao hn sccng ca si ng nano carbon. Tht vy, gi tr ny khin chng bn hn Kevlar gp 30 ln v

bn hn cotton 224 ln, Peng ni.

V cha ht: cc ng carbon khng l tht do v c th ko cng ra, khin chng tht

hp dn cho cc ng dng yu cu dai cao. Chng cng c dn in cao vo c 10 3


20/50


siemen/cm nhit phng, so vi 102siemen/cm i vi cc si nano carbon a thnh. S

dn in cng tng theo nhit , hm rng cc ng ny l cht bn dn.

Tt c nhng tnh cht tuyt vi ny c ngha l cc ng dng c th tht a dng, bao

gm o gip chng n nh cn, nh cc o vest chng n; cc hn hp chu bn cao c th

nh hnh thnh cc b phn cho cc loi xe nh cn v hiu sut cao; cc h v my mc viin t; v vi vc siu bn.

i nghin cu hin c k hoch tm hiu xem cc ng carbon khng l hnh thnh

nh th no v lm th no iu khin cu trc ca chng tt hn. Chng ti cng hi vng ci

thin cc tnh cht ca chng v nghin cu cc ng dng thc tin, Peng ni.

Belle Dum (physicsworld.com, 08/08/2008)

Du hiu trc tip nht ca nng lng ti ?

N chim chng ba phn t thnh phn khi lng-nng lng ca v tr v n l

nguyn nhn gy ra s gia tc, nhng l tt c ci chng ta bit v nng lng ti. Vy th

lm th no chng ta dm khng nh chc chn c du hiu trc tip nht cho nng

lng ti t trc n nay ?physicsworld.comi tm li gii thch cn k.


21/50


Istvn Szapudi v cc ng s ti trng i hc Hawaii ang khng nh c du hiu trc tip nht t trc

n nay cho nng lng ti, thc th b n chim chng ba phn t thnh phn khi lng-nng lng ca v tr.

Hnh ny cho thy nn vi sng v tr (CMB) vi v tr ca cc siu chn khng (cc vng trn mu xanh dng)

v cc siu m (cc vng trn ). Bng cch so snh nhit ca cc photon CMB t nhng vng ny, i ca

Szapudi c th o c sc cng ca cc siu m mt hin tng gi l hiu ng Sachs -Wolfe Tch hp

hnh thnh t nng lng ti.

Ai ara khng nh ?

Mt nhm nh thin vn vt l ng u l Istvn Szapudi ti trng i hc Hawaii.

H phn tch nh le li ca cc photon vi sng pht ra t khng gian v thy kch thc ca

cc siu m thin h nng thay i theo thi gian. Nu v tr ca chng ta l phng v

cc quan st cho thy tht s ng l nh vy th l thuyt hp dn ca Einstein tin on

kch thc siu m s gi nguyn khng i. Tuy nhin, cc nh nghin cu Hawaii nhn

thy cc siu m v ang b ko cng ra ngoidu hiu xc nhn ca nng lng ti y

hp dn.

iu ny khng xy ra hng ngy, nht l vi cc nh l thuyt nh chng ti, nhng

ngi ch yu lm vic vi cc khi nim ton hc tru tng - Istvn Szapudi, i hc

Hawaii

H phn tch cc photon nh th no ?


22/50


Cc photon vi sng trong cu hi, gi l phng nn vi sng v tr (CMB), trn ngp

ton b v k t khi vt cht v bc x ln u tin tch nhau ra chng 380.000 nm sau Big

Bang. Tht ra, nh le li ca CMB u ti mc cc nh thin vn vt l c th s dng n

minh ha cho ng lc hc ca nhng cu trc ln nh cc m v siu m thin h. Ly d

liu t mt danh mc thin h gi l Sloan Digital Sky Survey, i ca Szapudi lp th

v tr ca cc siu m trn mt bn ca CMB. Sau , h c th so snh bn CMBtrng nh th no nhng vng c cc siu m vi nhng vng c khng gian trng rng,

hay siu chn khng.

Lm th no s so snh cho thy cc siu m ang b ko cng ra ?

Theo cch tng t vic bn thu c th nng hp dn khi bn i b ln mt ngn

i, mt photon thu c nng lng khi n i mt trc mt c nhy ln trong s hp dn

ca mt siu m. Ngi ta c th ngh rng photon s mt cng lng nng lng khi n

i sang v khc. Tuy nhin, nu nh siu m b ko cng khi photon ang i qua n, thphoton s chu mt s thay i nh hn lc hp dn khi n i ra so vi khi n i vo. Ni

cch khc, photon s vn gi c mt cht nng lng thu thm ca n. Szapudi v cc

ng s cc photon hi giu nng lng tnh hn mt cht ny bng cch theo di

nhit . S khc bit khng ln ch khong mt phn triu ca mt Kelvin.

C phi i ca Szapudi l nhng ngi u tin trng thy nng lng thm ny ?

Khng. Hin tng c gi l hiu ng SachsWolfe Tch hp (ISW), v tng

s dng n kho st ng lc hc ca cc siu m c xut ln u tin bi cc nhv tr hc Rob Crittenden v Neil Turok trong lc h lm vic ti trng i hc Princeton

vo nm 1995. K t y, mt nhm nh cc nh thin vn vt l ng u vi th thch,

bao gm cc i ng u l Bob Nichol v Crittenden thuc trng i hc Portmonuth

Anh, Enrique Gaztanaga thuc Vin Khoa hc Khng gian Ty Ban Nha v Nikhil

Padmanabhan thuc Phng th nghim Lawrence Berkeley M. Trong mt vi nm qua, cc

i nghin cu ny pht hin ra hiu ng ISW vi s tin cy tng dn.

C phi i ca Szapudi hin nay c sc tin cy hn ?

Vng, n khng hn l mt s tin cy thng k h khng nh pht hin ra hiu

ng ISW ch trn bn sigma (hay chc chn 99,9995%), cng c vi cc gi tr tin cy khc

bo co trong nm nay. Mt quan trng ca cng trnh ca cc nh nghin cu Hawaii l h

tp trung s ch ca h ln mt mu siu m v siu chn khng ln nht. Kt qu l mt

tn hiu r rng hn, nhiu t hn v ng tin cy hn. Theo li ca Szapudi: Chng ti

tht s m ti. N l mt hiu ng rt nh v tinh vi, v y l ln u tin chng ta c th tht


23/50


s nhn thy n, tht khc hon ton vi vic pht hin ra n t cc s liu thng k mang tnh

tru tng hn.

Vy ti sao n l du hiu trc tip nht ca nng lng ti ?

C nhiu cch lun ra nng lng ti, nhng hu ht u da trn cc hiu ng quy

m ln v cc gi thuyt ngi ta tha nhn, khng chng minh. V d, s gia tc v tr (v

do nng lng ti) ban u c pht hin vo nm 1998 bi vic nhn vo nh sng tn li

ca cc sao siu mi xa xi, nhng c ch chnh xc n sau s bng n sao siu mi chnh n

cha c bitr. Mt s ngi nghi ng cch gii thch nng lng ti ca cc quan st sao

siu mi , tt nhin, nhng chim s ng, v h chng thc thi gian v li thi gian

bng nhng k thut khc. Cc quan st v hiu ng ISW khng nhng l b phn ca s

chng thc , m c l trc tip theo ngha chng lin h vi s tng trng ca tng cu

trc ring l.

Nhit ca cc siu m (hnh bn phi) ln hn so vi cc siu chn khng (hnh bn tri) cho Szapudi v cc

ng s ca ng bit rng cc sium ang b ko cng ra bi nng lng ti.

Ngi ta phn ng g vi cng trnh ?

Szapudi l mt ngi d chu. Sau khi ng t thuyt phc chnh mnh rng cc kt qu

l s tht vo thng 2 nm nay, khong thi gian sinh nht ln th 42 ca ng, i nghin

cu ca ng tng ng mt chic bnh sinh nht c hnh dng ca mt m nng v lnh

trong CMB. Ngoi l bui tic, Nichol thuc nhm Portsmouth ngh rng i nghin cu

Hawaii a ra phn tch c l hon chnh nht ca hiu ng ISW t trc n nay.


24/50


Nichol cng m t nm 2008 l nm m mn ca hiu ng ISW v cc nhm ang nghin

cu v hiu ng ISW ngy nay u ng vi sc mnh v tnh xc thc ca d liu .

Vy u l bc tip theo cho hiu ng ISW ?

Cho n khi cc cuc kho st thin h chnh xc hn c cng b, c kh nng n s

xut hin trong thp k ti, cn c nhiu vic phi lm t quan im ca cc nh thin vn vt

l. Tuy nhin, cc nh l thuyt c th c v s thch th vi vic kho st cc phn tch bi

Szapudi v nhng ngi khc th v i tm mt s hiu bit tng tn hn v bn cht ca

nng lng ti. Quan im hin nay dng nh c tnh bc ngoc ch ng h mt hng s

v tr biu hin di dng mt nng lng chn khng, mc d c mt vo s la chn khc

na. Mt l l thuyt hp dn ca Einstein thuyt tng i rng khng hon chnh 100%

v cn c sa li gii thch s gia tc v tr. Hiu ng ISW c bit tt cho vic kim tra

cc l thuyt hp dn ci tin nh th v n xt c th n cng biu kin ca lc hp

dn trn nhng thang o ln.

Bn tho ca cc quan st v hiu ng ISW bi nhm ca Szapudi c th tm ti

arXiv:0805.3695v2varXiv:0805.2974v2. Ngoi ra, cn c bn tho ca nghin cu gn y

bi nhm ca Padmanabhan tiarXiv:0801.0642v nhm ca Nichol tiarXiv:0801.4380v2.

http://arxiv.org/abs/0805.3695v2http://arxiv.org/abs/0805.3695v2http://arxiv.org/abs/0805.2974v2http://arxiv.org/abs/0805.2974v2http://arxiv.org/abs/0805.2974v2http://arxiv.org/abs/0801.0642http://arxiv.org/abs/0801.0642http://arxiv.org/abs/0801.0642http://arxiv.org/abs/0801.4380http://arxiv.org/abs/0801.4380http://arxiv.org/abs/0801.4380http://arxiv.org/abs/0801.4380http://arxiv.org/abs/0801.0642http://arxiv.org/abs/0805.2974v2http://arxiv.org/abs/0805.3695v2


25/50


LHC trng thy nhng chm proton u tin

m mu vng l tit din ca mt trong cc chm proton c bm thnh cng vo LHC hi cui tun qua.

Cc nh vt l ti phng th nghim CERN gn Geneva ang bt u tun lm vic vi

mt ma xun tinh thn trong cc bc cng vic ca h, bm thnh cng nhng proton

u tin vo My Va chm Hadron Ln (LHC) vo cui tun qua. Php kim tra thy ccproton chuyn ng 3 km qua mt trong tm phn khu ca LHC, bo tin tt lnh cho vic khi

ng hp thc vo hm 10 thng 9.

C nhiu ngi rt hnh phc trong ngy hm nay, ngi pht ngn CERN James

Gillies ni. Php kim tra khng th no tin trin tt hn c na.

Mc ch chnh ca vic bm th l ng b ha LHC vi cc my gia tc nh hn s

cung cp proton cho n. Khi c my khi ng v hot ng, cc nam chm xung phi kch

cc chm proton t my gia tc ny sang my gia tc khc vi chnh xc nano giy.

Lc 15:20 ngy th su, mt chm nh proton c trch thnh cng khi Super

Proton Synchrotron (SPS) bng mt nam chm xung v gi qua 2,7 km ng truyn di ti

LHC. Sau , lc 21:40, sau vi gi nh gi qu trnh, mt chm proton c trch ra khi

ng truyn i vo LHC trong - trc s ngc nhin ca nhiu ngi n truyn i

khong 3 km cho n khi b dng li bi mt mn hnh (xem nh).


26/50


S truyn chm proton ln u tin gy ra mt s hng th trong phng iu

khin, v ru mng c khui np, ngi iu hnh c my Roger Bailey pht biu vi

physicsworld.com. Chng ti trng i xu cc proton thnh vng bng cc my d v tr v

cc nam chm hiu chnh cc b, nhng lc ny chng ti bit cc trng v s phn cc ca

vi trm nam chm siu dn l rt tt.

Php kim tra c lp li vi ln vo hm th by, mang li cho i iu hnh rt

nhiu d liu gip cho vic khi ng sun s nht c th. Mt php kim tra tng t i vi

cc proton chy theo hng khc (ngc chiu kim ng h) c ln k hoch vi cui

tun 22 thng 8.

S khi ng y xc ng

Trong cuc tm kim ca n hng ti cc ht c bn mi, LHC s to ra cc mt

nng lng cao nht t trc n nay tng c to ra trong phng th nghim. Nhng d n khng c trin khai sun s, vi cc trc trc k thut khng th trnh c v chi ph leo

thang buc c my phi tr hn t nht l nm nm so vi lch nh.

Nay, sau gn ba thp k ch i - na thi gian trong s tiu tn ch tp my va

chm CHF6bn v cc bn my d ht khng l ca n CERN ang vo giai on kt thc

mt hnh trnh di. Hu nh ton b 1600 nam chm siu dn s dn cc proton chy xung

quanh vnh ai LHC c lm lnh ti nhit hot ng ca chng l 1,9 K. Bc tip

theo l chng 1400 php kim tra phn cng v kim tra in phi c tin hnh trong vi

tun ti cho n khi c my hon ton sn sng i vo hot ng vo ngy 10 thng 9.

Vo ngy khi ng, i iu hnh 24/7 s c gng a mt chm n, cng thp

cha vi t proton vo chy trong chu vi 27 km ca LHC. Sau , h s thc hin cng vic

tng t theo hng ngc li, c l mt vi ngy c thy. Sau , h s iu chnh cc nam

chm sao cho cc proton c th d dng quay trn trong nhng khong thi gian hng gi m

khng thay i hnh trnh.

Sau , cc nam chm hi t mnh s mang cc chm ang quay ngc chiu kim

ng h vo va chm ti bn im tng tc ca LHC (yu cu chm tia phi c cu hnhtrong bn chm). Thot u, cc chm s c nng lng 450 GeV (nng lng m cc proton

c bm vo t my SPS), sn sinh ra cc va chm 900 GeV. Nhng mc tiu ca nm nay

l cung cp cc va chm ph k lc 10 TeV (5 TeV/chm tia) vi 43 chm, mi chm cha vi

chc t proton. Nu tt c u sun s, th d liu LHC u tin c th khi ngun cho cc th

nghim ng ngay ngy khnh thnh LHC chnh thc vo hm 21 thng 10.


27/50


LHC s ngng hot ng vo ma ng, trong thigian cc nam chm un cong

ch yu s c hun luyn iu khin cc chm ht nng lng y 7 TeV (sn ra

cc va chm 14 TeV) vo thng 3 hoc thng 4 nm 2009. Khi c my hot ng sc mnh

trn vn ca n, gn 3000 chm ht mi chm cha ti 100 t proton c th cho chy vng

trn trong mi hng, sinh ra na t va chm mi giy. Cht lc qua cc mnh v, cc nh vt

l hi vng tm c vt tch ca cc ht nh boson Higgs - ht s hon thin m hnh chunca ngnh vt l ht hay cc thc th cn k l hn na nh cc l en v cc chiu khng

gian khc na. Tuy nhin, c kh nng s mt t nht l mt nm cho cc nh vt l cp nht

d liu v tm hiu cc my d ht ca h tt m bo rng h ang trng thy s

tht.

Matthew Chalmers (physicsworld.com, 11/08/2008)

Camera chp nh tc k lc

Cch nay chng 130 nm, mt thng nhn giu c chiu m chuyn gia nhip nhngi Anh Eadward Muybridge gii quyt, mt ln v cho mi mi, mt cu hi ph binthi l con nga c nhc c bn chn ca chng ln khi mt t cng mt lc hay khngkhi chng phi nc i. Trang b c t hay ngn y camera vi mt c ch mn chn tinh xo,Muybridge khng nhng chng minh c rng nhng con nga ang phi nc i tht s cnhng thi khc chng vnh trong khng trung, m ng cn chng minh c mt cchphi sng hnh nh trong vng hai phn nghnca mt giy.

Chp nh tc cao tin mt bc di k t , v n c s dng cho nhngcng vic i thng hn,v d nh gii cc kim nghim va chm, nghin cu n o v csinh hc. Cc h thng hin i c th chp cc bc nh hng trm nghn ln mi giy phn gii cao, hay thm ch hng triu ln mi giy phn gii thp hn. Nhng nay ccnh nghin cu Jordan v M va tin ti mt h c tim nng cho kt qu tt nht thuc chai th gii. L s kt hp ca cht lng hnh nh, tc khung hnh v s khung hnh, cho

nn h camera [ca chng ti] c kh nng l cha c tin l, theo li Ala Hijazi thuctrng i hc Hashemite.

Vn ch yu i km vi vic thu c tc khung hnh cao trong chp nh l cccamera, trn tng th, chm phn ng. C kh nng thu c cc bc nh tc thi bng cch cho mt camera phi sng thng xuyn trong bng ti v sau ch thp sng i tngquan tm trong mt khonh khc vi mt n flash. Tht khng may, nu nguyn tc nyc m rng vi nhiu camera v n flash hn, th kt qu l mt chui phi sng bi lnxn.


28/50


Cc bc sng chn lc

Hijazi v ngi ng s ca ng, Vis Madhavan thuc trng i hc Bang Wichitanhn thy h c th gii quyt vn ny bng cch s dng bn kt hp camera -v-flash chnhy vi mt bc sng nht nh 440, 532, 600 hoc 650 nm. iu ny ngha l micamera c th thu c hnh nh tc thi ring ca n m khng c s giao thoa ca ba hnhkia.

Khi nim ny cho php phn tch thi gian gia tng bc nh c chp n nht xu, Hijazi gii thch. [N] mang li mt h camera c th chp mt chui hnh nh phngii cao tc cc cao.

H thng nguyn mu ca Hijazi v Madhavan s dng cc dng c tch in ghp(CCD) cho cc camera v hp i ngu, laser Nd:YAG cho cc flash c kh nng to ra bnnh lin tip 200 MHz (200 triu ln mi giy), hoc 8 hnh mi giy 8 MHz (Meas. Sci.Technol.19 085503). Tuy nhin, Hijazi ngh rng h thng s c kh nng chp cc bcnh phn gii 100 megapixel trong ngng gigahertz. iu ny s khin n nhanh hn ccamera in t tc cao, chng ch c th to ra tc khung hnh vo c 100 kHz, lncamera trng quay hoc gng quay, chng c th to ra cc bc nh phn gii thp tc

ln ti 20 MHz.Cc nh nghin cu nghh thng ca h s c ch trong vic chp nh cc cht liu

trong qu trnh gia cng tc cao. H va thnh lp mt cng ti tn gi l Spectrum OpticalSolutions, theo h ni n s bt u tip th h thng camera tc cao trong qu hai nm ti.

Marie Freebody (physicsworld.com, 12/08/2008)

S ri vn l mt b n

Nu hai ht b ri, nh c hc lng t bo th, th bt k mt thay i no vi ht

ny cng c th gy ra mt s thay i tc thi ht kia, cho d chng cch nhau bao xa

chng na.

Einstein bc b quan im ny l tc dng ma qu t xa. Nhng iu g s xy ra

nu nh c hc lng t khng ng lm - s thay i khng phi l tc thi, m b thc y

bi mt tn hiu truyn i gia hai ht b ri ? Nay th mt th nghim tin hnh Thy S va

cho thy rng, nu mt tn hiu nh th tht s tn ti, th n s phi truyn i t nht l nhanh

nh nh sng, v c kh nng l nhanh hn hng nghn ln.

Th nghim , c thc hin bi Nicolas Gisin v cc ng s n t trng i hc

Geneva, ging nh cc th nghim khc c gng kim tra s ri, mc d quy m ln hn.
http://www.iop.org/EJ/abstract/0957-0233/19/8/085503http://www.iop.org/EJ/abstract/0957-0233/19/8/085503http://www.iop.org/EJ/abstract/0957-0233/19/8/085503http://www.iop.org/EJ/abstract/0957-0233/19/8/085503http://www.iop.org/EJ/abstract/0957-0233/19/8/085503http://www.iop.org/EJ/abstract/0957-0233/19/8/085503http://www.iop.org/EJ/abstract/0957-0233/19/8/085503http://www.iop.org/EJ/abstract/0957-0233/19/8/085503http://www.iop.org/EJ/abstract/0957-0233/19/8/085503http://www.iop.org/EJ/abstract/0957-0233/19/8/085503


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Cc nh nghin cu trc ht lm ri hai photon ti Geneva, v sau gi chng i 9 km theo

nhng hng ngc nhau sang ng v sang ty - n cc giao thoa k t ti cc ngi lng

Thy S Jussy v Satigni. Ti nhng ni ny, h tm bt k s giao thoa no gia cc photon.

Nu s giao thoa trn mt mc hp l cho bi ci gi l bt ng thc Bell th n hm

rng cc photon ang thay i tnh cht ca chng mt cch tc thi tng hp vi nhau.

nh chp t khng trung ca Geneva v cc ngi lng Satigny v Jussy

Bt k h quy chiu no

Trn phng din ring ca n, th nghim ny s khng loi tr kh nng rng cc

photon ang gi tn hiu cho nhau. y l v, theo thuyt tng i c bit ca Einstein, cc

php o khng th no tc thi t im nhn ca mt ngi quan st hay mt h quy chiu

ang chuyn ng. Ni cch khc, c th c mt cht thi gian hu hn cho tn hiu truyn i.

gii quyt vn ny, Gisin v cc ng s tin hnh th nghim ca h nhiu

ln trong khong thi gian 12 gi. Chuyn ng quay ca Tri t trong sut thi gian ny

ngha l cc nh nghin cu c th thit t mt gii hn ln khong thi gian i vi bt k h

quy chiu no. H nhn thy thm ch i vi mt h quy chiu to ra khong thi gian ln

nht - mt h quy chiu chuyn ng tng i so vi Tri t gn tc nh sng th bn

thn tn hiu phi truyn i nhanh hn 10 ln tc nh sng. i vi cc h quy chiu thc t

hn na v d, mt h quy chiu ang chuyn ng tng i so vi Tri t tc mt

phn nghn tc nh sng th tn hiu s phi truyn nhanh hn na, gp 10.000 ln tc

nh sng (Nature454 861)

Gisin pht biu vi physicsworld.com rng cng trnh ca i nghin cu ca ng, ln

u tin kh nng bt k mt h quy chiu gi thuyt no c a vo tnh ton, xc nhn

cc tin on ca thuyt lng t. ng cng hi vng n s cho php cc nh nghin cu khc

tm ra mt li gii thch c th d chp nhn hn cho cc b n ca s ri.

Gisin toldphysicsworld.comthat his teams work, which is the first time the possibility

of any hypothetical reference frame has been taken into account, confirms the predictions of

quantum theory. He also hopes it will enable other researchers to find a more palatableexplanation for the mysteries of entanglement.



30/50


Cc spin electron to nn mt kim loi c o

Cc tp cht manganese trong FeSi c moment t spin 1 (mi tn mu xanh), cn cc l trng do chng to ra c

moment t spin 1/2 (mi tn mu cam).

Mt i cc nh vt l quc t va bin i mt cht liu bn dn thng dng thnh

mt loi c o ca kim loi gi l cht lng phi Landau-Fermi.

Trong khi y khng phi l kim loi u tin nh th c to ra, nhng i nghin

cu khng nh n l cht u tin c th m t bng mt m hnh l thuyt n gin. Cht ny

c th gip cc nh vt l tm hiu cc cht lng phi Landau-Fermi phc tp hn nh cc cht

siu dn nhit cao v cn c th a n nhng phng php mi iu khin cc electron

phn cc spin.


31/50


Mt trong nhng tnh cht ng ch nht ca tn electron dn ring l trong a s

cc kim loi l chng c v lan truyn i m qun mt thc t chng b nhi nht bn trong

mt mng cht rn cng vi 1022electron v ion khc. Thay v ny bt t va chm ny sang va

chm tip theo, cc electron dng nh chy m i qua kim loi ging ht nh mt cht lng

chy qua mt ng dn.

Cc electron khng tng tc

Hnh trng ny ln u tin c gii thch vo nm 1956 bi nh vt l ngi X Vit

Lev Landau, ngi cho rng nh hng ca cc tng gic gia cc electron c th gii thch

bng cch m t h l mt tp th cc electron khng tng tc, gi l cc gi ht, mi ht

c mt khi lng tc ng ln hn khi lng ca mt electron t do.

M hnh Landau-Fermi xy dng trn quan nim che chn rng cc lc tnh in

bn trong mt m my electron tch in m b trit tiu chnh xc bi cc ion tch indng. Tng t, cc tng tc gia cc moment t spin ca cc electron v ion cng b che

chn.

L thuyt cht lng Landau-Fermi cc k thnh cng vic m t hnh trng ca cc

h bin i nh cc kim loi v helium lng. Tuy nhin cc nh vt l pht hin thy mt s

lng nh nhng tng dn ca cc cht trong cc electron chuyn ng t do, nhng khng

th m t bng m hnh cht lng Landau-Fermi. ng ch nht l cc cht siu dn nhit

cao gc ng, chng t ra rt kh hiu.

V th, cc nh nghin cu tp trung vo tm hiu cc tnh cht ca cc cht lng phi

Fermi nh th, nhng cho n nay vn cha tm c mt h n gin c th nghin cu c

thc nghim ln l thuyt.

L thuyt n gin

Nay Gabriel Aeppli ti Trung tm Cng ngh Nano London v trng i hc College

London, v cc ng s ti trng i hc quc gia Lesotho, i hc Bang Louisiana v

Phng th nghim Bell New Jersey, va pht hin thy st silicide (FeSi) pha tp c th lmt cht lng phi Fermi. Hn th na, h ni rng hnh trng c th tin on bng mt l

thuyt n gin (Nature454 976).

FeSi l mt cht bn dn khe nh c nghin cu rng ri v cc c tnh quang v

in t ca n c th d dng bin i bng cch pha tp n vi cc tp cht nh nhm v

cobalt. Trong khi s pha tp ny to ra s mt trt t trong cht liu, th cc mu FeSi trc

y c nghin cu l cc cht lng Landau-Fermi.
http://www.nature.com/nature/journal/v454/n7206/http://www.nature.com/nature/journal/v454/n7206/http://www.nature.com/nature/journal/v454/n7206/http://www.nature.com/nature/journal/v454/n7206/http://www.nature.com/nature/journal/v454/n7206/http://www.nature.com/nature/journal/v454/n7206/http://www.nature.com/nature/journal/v454/n7206/


32/50


Trong cng trnh mi ny, Aeppli v cc ng s pha tp FeSi vi cc nguyn t

manganese, ng gp mt nhn ion vi mt moment t spin bng 1. Tuy nhin, mi tp cht

manganese cng to ra mt l trng tch in dng, n l mt gi ht c moment t spin

1/2. iu ny ngha l moment t spin ca cc tp cht khng th no b che chn trn vn bi

spin ca cc l trng.

S nhp nhnglng t

Ti nhng nhit rt thp ch vi ba Kelvin, c hc lng t tuyn b rng mt s

tp cht manganese s hon ton b che chn, trong khi phn cn li th khng c che chn

ht. Theo Aeppli, s nhp nhng ch tp cht no b che chn mt thi im nht nh ngha

l cc gi ht trong cht liu khng th tn ti cp thi gian lu to thnh mt cht

lng Landau-Fermi.

i nghin cu xc nhn iu ny bng cch o dn in ca cht pha tp l hmca nhit . dn ca mt cht lng Landau-Fermi mt trt t lun bin i theo cn bc

hai ca nhit , nhng khng phi l trng hp ca FeSi pha tp manganese. i nghin

cu cng thit t mt t trng tng i yu ln mu vt lm cho cht dn in ging

nh mtcht lng Landau-Fermi mt trt t. i nghin cu tin rng cc spin manganese c

xu hng t sp thng hng theo hng ca t trng, do loi tr s nhp nhng c lng

t.

Theo Aeppli, ngi ta c kh nng khai thc hiu ng ny trong cc dng c in t

trong dng in chy qua mt tip gip c th chuyn i gia mt cht lng Landau -Fermi v mt cht lng phi Landau-Fermi. Cc dng c nh th c th tm thy cng dng

trong nhng mch in t-cng ngh spin s dng c in tch v spin ca electron x l

thng tin.

S nhp nhng lng t ny l mt th d ca s ri lng t - mt qu trnh thit yu

cho s hot ng ca cc my tnh lng t. Nh mt h qu, Aeppli tin rng hiu ng ny c

th s dng iu khin vic dch thng tin lng t t cc electron tnh ti tm thy gn

nhn ca cc ion sang cc electron ang chuyn ng.



33/50


Cc trch dn c gip sng lc cho gii thng Nobel ?

Thng 10 ti ng ngha mt cu hi tr gi 10 triu kronor s ti: ai s l ngi tip

theo ginh c gii thng Nobel Vt l nm 2008 ?

Tt nhin, mi ngi hm m vt l c mt quan im chia s. Nhng nu mtnghin cu do cc nh nghin cu Canada thc hin l ng vi mi trng hp, th ng l

kh m d on v c l c chn la nhng ngi thng gii hm nay hn nhiu so vi

na th k trc.

Yves Gingras v Matthew Wallace ti trng i hc Quebec, Montreal, da trn

nghin cu v s liu trch dn ca nhng ngi ot gii Nobel vt l v ha hc t k t khi

m gii nm 1901, khi Wilhelm Rntgen ginh c gii thng vt l u tin cho khm ph

ra tia X, cho n nm ngoi, khi Albert Fert v Peter Grnberg cng nhn gii thng vt l

cho khm ph ca h ra hin tng t tr khng l.

S dng s liu ny, Gingras v Wallace xp hng nhng ngi ot gii trong s

nhng ngi ng thi ca h theo mc thng xuyn m cc bi bo ca h c trch

dn bi nhng ngi khc, v sau phn tch nhng th hng thay i nh th no theo

thi gian. Kt qu l mt danh sch tng nm lin tip ca cc nh khoa hc c sc nh hng

nht, t cc nh nghin cu c th so snh vi vic trao gii thng Nobel.

Kh on hn bao gi ht

Tnh n nm 1945, phn tch ca Gingras v Wallace miu t sinh ng cc nh

ot gii Nobel l nhng ngn n sng trong vt l hc (xem biu ). S liu h l cho thy,

trong tin trnh s nghip ca cc nh khoa hc , cc xp hng trch dn ca h t cc i

khong mt nm trc vic cng nhn gii Nobel ca h, chng t h l mt ngi ca thi

qua. Sau khi h nhn gii thng, th hng ca h gim i t t - c l, theo Gingras v

Wallace, do s ym tr ca danh ting hay hiu ng ho quang ca vic l mt ngi thng

gii.

Tuy nhin, sau 1945, th n l mt cu chuyn khc ri. Vi mi nm tri qua, th

hng ca cc nh ot gii Nobel c gim dn v gim dn cho n khi kh m phn bit h

vi nhng nh khoa hc hng u khc. Tht vy, trong thi k t 1971 n 2007, dng nh

khng khng c cc i no trong th hng trch dn ca nhng ngi ot gii Nobel c

(arXiv:0808.2517).
http://arxiv.org/abs/0808.2517http://arxiv.org/abs/0808.2517http://arxiv.org/abs/0808.2517http://arxiv.org/abs/0808.2517


34/50


Biu th hng ca cc nh ot gii Nobel vt l, theo s trch dn ca h, theo hng nm. ng lin ntthng ng biu din nm 0 khi gii thng bt u trao.

Gingras v Wallace gii thch cho s thiu vng cc nh ot gii xut sc vi s lng

tng dn ca cc ngnh con trong khoa hc: R rng l khoa hc pht trin theo hm s

m trong th k 20 n chng mc m cc phn vng ca khoa hc khin ngy nay kh hn

nhiu so vi bao gi ht vic nhn ra mt ngi ot gii r rng cho mt ngnh hc tng th.

Trong khi khong nm 1910 vn tng i d dng bit c ai l nh khoa hc quan

trng nht trong mt ngnh hc, th vic nh kh khn hn nhiu k t t nht l thp nin

1970.

D on hu nh v ngha

Phn tch lm tng thm nghi vn liu gii thng Nobel vt l c cn uy tn nh n

gi c trong na u ca th k 20. Gingras v Wallace khng tip tc khai ph mi quan h

ny, mc d h tht s cho thy rng y ban Nobel c thi gian vt v hn nhiu trong vic

chn ra ng c vin xut sc nht; iu ny c th thy r thc t l chng c gii thngno m khng chia s trong 15 nm qua. Tt nhin, h ni tr chi d on hu nh l v

ngha.

Tuy vy, cc nh nghin cu lng trnh thc t l gii thng Nobel, nh mt quy

lut, c trao trn c s mt khm ph, khng phi trn din mo ca chng trn cc bng


35/50


xp hng. Nh Arne Tiselius, cu lnh o ca y ban Nobel ha hc, c ln vit: Bn khng

th trao gii Nobel cho ci ti gi l hnh vi tt trong khoahc c.


Cc ngi sao tr nng khng tun theo cc lc thy triu

Trng thi cui cng ca m phng ca mt m my kh c khi lng 100.000 Mt tri. Cc vng sng muvng l nhng cm kh m c cui cng s tr thnh nhng ngi sao nng.

Cc nh thin vn vt l t lu nghi vn ti sao tm ca thin h ca chng ta li

ng c cc ngi sao tr nng m, ngi ta c th ngh, khng th no hnh thnh gn l


36/50


en siu trng nm ti trung tm ca n. Tuy nhin, nay th b n c l c gii quyt bi

hai nh nghin cu Scotland.

H tin hnh cc m phng my tnh cho thymt s cht kh xoy cun vo l en

c th hnh thnh nn nhng cm dy c quay trn nhng khng bin mt vo trong l

en trc khi chuyn bin thnh nhngngi sao nng. Nghin cu c th ci thin s hiubit ca chng ta v s hnh thnh sao cng nh cc l en siu trng.

Khm ph bt ng

Cc nh thin vn bit khong chng mt thp k nay rng li ca nhiu thin h

trong c Di Ngn h ca chng tacha cc l en siu trng. Khm ph c thc hin

bi vic lp biu chuyn ng ca cc ngi sao rt sng v rt nng ng c trong vng

gn tm ca Di Ngn h.

Nhng chng bao lutrc khi cc nh thin vn vt l bt u nghi vn lm th no

nhng ngi sao c mt vo lc ban u. Cc l thuyt thng thng ca s hnh thnh

sao xut rng cc lc thy triu d di s cn tr cc ngi sao hnh thnh gn mt l en

siu trng v cc ngi sao hnh nh qu tr c to ra u v sau b ht vo

tm thin h.

Cc m phng mi, tin hnh bi Ian Bonnell ti trng i hc St Andews v Ken

Rice n t trng i hc Edinburgh, xut rng cc ngi sao tht ra c hnh thnh

gn l en. H cn tm thy qu trnh ng h s hnh thnh nhng ngi sao nng trn cc nghnh nh hn ca chng, n c th gii thch ti sao li ca thin h ca chng ta nhng

khng phi phn cn li ca n b thng tr bi nhng ngi sao rt ln (Science321 1060).

Hai m my khc nhau

Trong cc m phng ca h, Bonnell v Rice s dng hn mt nm thi gian my

tnh trn mt siu my tnh SGI Altix d on ci s xy ra khi hai m my kh kch c

khc nhau (mt khong 10.000 ln khi lng ca Mt tri v mt khong 100.000 ln khi

lng ca Mt tri) b ht vo trong mt l en.

M phng cho thy trng hp dn mnh ca l en (bn thn n khong 1 triu ln

khi lng ca Mt tri) lm nng cht kh ang b ht vo, gy ra sng sc truyn nng

lng xuyn ra ngoi xa l en. Cc sng ny dng nh lm lch n 90% cht kh ang b

ht vo thnh mt a hnh oval quay xung quanh l en vi phn kh cn li bin mt vo

trong vc thm a ngc.
http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/


37/50


M phng cng ln theo s tin trin ca cht kh trong a. H tm thy cc lc

thy triu d di ca l en lm nng cc cm kh, lm tng p sut ni ca chng. Ch nhng

cm ln nng lng hp dn mi vt qua c tc dng p sut ca s nng thy triu,

l nguyn dotheo Bonnell v Rices hnh thnh nhng ngi sao ln c u tin.

Cc qu o lch tm gn

Cc nh nghin cu t trc n nay kim tra hai loi m my kh b ht vo c

th c. Loi th nht, gm cht kh khi lng 100.000 ln khi lng Mt tri, cho thy

khong 200 ngi sao vi khi lng t 10 n 50 ln khi lng ca Mt tri s c hnh

thnh trong qu o lch tm gn quay xung quanh l en. Tuy nhin, mt m phng th hai,

gm m kh 10.000 ln khi lng Mt tri, tht bi vic to ra s ln t ca cc ngi

sao nng v thay v th cho rng ch yu cc ngi sao c Mt tri s c hnh thnh cch xa

l en hn na.

Cc kt qu ny ph hp vi hai tnh cht c bn ca nhng ngi sao tr trong tm

ca Thin h ca chng ta: khi lng cao ca chng v cc qu o lch tm ca chng xung

quanh l en siu trng, Bonnell ni.

Mt hn ch ca nghin cu l n ch xem xt hai trong nhiu hnh dng v kch c c

th c ca cc m my kh c th ri vo trong mt l en. i nghin cu hin c k hoch

m phng thm mt vi kch bn khc na tm hiu mi quan h gia s hnh thnh sao v

cc iu kin ban u ca m my kh.

Reinhard Genzel, mt trong cc nh thin vn ban u khm ph ra l en siu

trng caDi Ngn h, pht biu vi physicsworld.com rngm phng s m rng hn

na hiu bit ca chng ta v cc l en siu trng v mi quan h ca chng vi s hnh

thnh ca cc thin h v cc cu trc k l nh quasar.

Genzel tin rng nghin cu l thuyt v s hnh thnh sao gn cc l en hin nay

ang tr nn tinh vi v thc t chng ta c th trng i thu c mt s hiu bit

tng i y v nhng hin tng cc k gy hoang mang ny trong tng lai rt gn.



38/50


Tc o spin c y ti gii hn

Cc nh nghin cu c va ngh ra mt phng php cc k nhanh lm bin i gi

tr ca mt bit d liu t bng mt dng electron phn cc spin.

H khng nh k thut ca h c th sm c s dng ch to cc b nh truy cp

ngu nhin t tnh (MRAM) nhanh nh cc chip nh thng thng v c mt lu tr

cao. Tin ch ln ca MRAM l chng vn gi c d liu ca chng khi tt i, ngha l

chng c th dng ch to cc dng c in t tit kim nng lng.

Cc chip nh nhanh thng thng, nh cc b nh truy cp ngu nhin ng v tnh

(DRAM v SRAM), cc bit d liu lu tr dng in tch trong nhng t in nh xu. Khi

ngun cp in ca chng tt i, d liu nhanh chng khng cn.

ng thi gy ra thi gian khi ng kh chu khi mt my tnh c bt ngun,

trong d liu c truyn t a cng sang b nh, b nh thng thng cn yu cu nhiu

nng lng ch lu tr thng tin.

Cc ct nano t tnh

a s cc nh ch to chip tin rng MRAM trong cc bit d liu c lu tr

trong cc ct nano nh xu ca cht liu t tnh mang li phng php tt nht ch to mt

b nh nhanh khng cn phi cp ngun mi lc.

a s cc MRAM s dng mt cun t tnh nh xu gn ct nano chuyn hng

t ha ca n v o bit t, v d, 0 sang 1. Tuy nhin, vic ch to cc cun nh phi

tht tinh vi thu c cc chip MRAM vi mt cao nh mt tm thy DRAM hay

SRAM.

Mt gii php l qun i mt cun to ln v thay v o ct nano bng cch cho truyn

mt xung electron phn cc spin i qua n. a s spin trong mt xung nh th hng theo

mt chiu c bit (ln hoc xung) v moment t ca chng tc dng mt moment quay

spin ln s t ha ca ct nano.

Tuy nhin, trong nguyn mu MRAM moment xon spin tng c ch to cho n

nay, qu trnh ny qu chm. Tr ngi l moment t dao ng khong 10 ns trc khi nm vo

s nh hng mi ca n, n lu hn thi gian hot ng thc t khong 10 ln.


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iu ny lm nn ch cc nh vt l, v trn l thuyt, ngi ta c th o s t ha

trong khong 1 ns.

o tc thi

Nay Hans Werner Schumacher v cc ng s ti phng th nghim tiu chun PTB

Braunschweig v trng i hc Bielefeld va chng t c rng bng cch iu khin thn

trng hnh dng thi gian v chiu di ca xung v bng cch thit t mt t trng nh

khng i mt ct nano c th o ch trong 1 ns (Phys Rev Lett101 087201). .

Shumacher pht biu viphysicsworld.comrng t trng t s t ha vo mt v

th r rng trong vic o chiu l d nht.

i nghin cu tin hnh cc th nghim ca h, s dng nguyn mu thng mi

MRAM moment quay spin ch to bi Singulus Nano Deposition Technologies Frankfurt.

Trong khi cc cun dy ngoi vn c s dng to ra t trng, th Schumacher tin rng

mt t trng tng t c th c to ra trong vng ph cn ca mi ct nano bng cch

thit k cn trng hnh dng ca bit nh.

Cng ngh thng mi

K thut ca chng ti l phng php u tin thu c s o chiu xc thc ch

trong mt nano giy, theo Schumacher, ngi tin rng k thut ca h c th c mt trong cc

MRAM thng mi vo nm 2010.

http://link.aps.org/abstract/PRL/v101/e087201http://link.aps.org/abstract/PRL/v101/e087201http://link.aps.org/abstract/PRL/v101/e087201http://link.aps.org/abstract/PRL/v101/e087201http://link.aps.org/abstract/PRL/v101/e087201http://link.aps.org/abstract/PRL/v101/e087201http://link.aps.org/abstract/PRL/v101/e087201


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Nh vt l nguyn tDavid Wineland c tng Huychng Khoa hc quc gia nm 2007 ca M

David Wineland (Geoffrey Wheeler)

Nh vt l hc nguyn t tin phong David Wineland l mt trong tm nh nghin cu

ngi M c trao tng Huy chng Khoa hc quc gia nm 2007. Wineland, mt nh vt l

ti Vin Tiu chun v Cng ngh quc gia (NIST), c ghi nhn cho s lnho ti tnhca ng trong vic pht trin ngnh khoa hc lm lnh bng laser v iu khin cc ion. ng

s nhn gii thng t tng thng George W Bush trong l trao thng th Washington,

vo ngy 29 thng 9.

Huy chng quc gia, do Qu Khoa hc quc gia (NSF) qun l v trao tng hng

nm, c Quc hi M thng qua nm 1959 tn vinh nghin cu khoa hc nng cao s

hiu bit ca th gii v a n nhng cch tn v cng ngh mang li cho nc M mt li

th kinh t ton cu.

Lm vic Boulder, Colorado, Wineland c ghi nhn cho nghin cu ca ng v

cc ng dng trong nhng php o v tiu chun cc k chnh xc, in ton lng t, v cc

php kim tra c bn ca c hc lng t, v cho nh hng to ln ca ng ln cng ng

khoa hc quc t qua vic o to cc nh khoa hc v cc n phm hng u.

Gip tch ring mt electron c thn


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K lc lu trong s cc t ph ca Wineland bt u nm 1973, khi l mt nghin

cu sinh tin s vi Hans Dehmelt ti trng i hc Washington, ng gip tch ra mt

electron c thn bng by Penning. Nm nm sau , Wineland khi ang ph trch

nhm nghin cu ring ca ng ti NIST Boulder thnh cng trong vic lm lnh bng

laser cc ion magnesium xung di 40 K.

Nghin cu ban u ny v cc ion b by nhm pht trin nhng phng thc khc

cho ng h chm caesium, i tng khi hnh thnh nn c s ca cc chun thi gian v

tn s quc t. Tuy nhin, cc k thut lm lnh v by ion m Wineland pht trin c mt tc

ng rng ln hn nhiu, lm pht sinh nghin cu v s lm lnh cc nguyn t trung ha

bng laser, cng trnh hnh thnh nn c s ca gii thng Nobel nm 1997 v 2001.

Sau , Wineland gip pht trin lnh vc in ton lng t thc nghim bi vic

chng minh c cng l gic lng t hai bit NOT-iu khin c u tin. Nghin cu

gn y tp trung vo vic vt qua cc ro cn a cc h vi ba qubit nh th vo trongmt my tnh lng t kch thc tht s.

Wineland l mt nh khoa hc li lc, ngi c nhng ng gp mang tnh cch

mng cho s pht trin v ng dng s lm lnh v by bng laser, theo li Katherine

Gebbie, trng Phng th nghim Vt l caNIST. Chng ti cm ng bi s ghi nhn xng

ng ny dnh cho ng.

Pht minh ra in ton lng t by ion

Cng c s tn dng t pha Winfried Hensinger, v ging vin thm nin v l

trng nhm Cng ngh Lng t Ion ti trng i hc Sussex Anh. Dave Wineland tht

s pht minh ra in ton lng t by ion, phng php thc nghim thnh cng nht tng

c s dng tnh cho n nay, ng ni. Hensinger m t gii thng l qu chm tr v

lu rng Wineland ni tri ch ng m mnh trong nhng kt qu tm c ca nhm

ngng lun lun bit chnh xc ci g ang dinra trong phng th nghim.

Margaret Harris (physicsworld.com, 26/08/2008)


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Nh nghin cu bt nhit hch mt chc gio s

Rusi Taleyarkhan

Trng i hc Purdue M va cng b h s ph trut Rusi Taleyarkhan sau khi

mt y ban ni b phn quyt hi thng 7 rng ng gian ln trong khoa hc.

Taleyarkhan, mt k s ht nhn ngi khng nh pht hin ra bt nhit hch hi

nm 2002, s mt danh hiu gio s Al Bement v k thut ht nhn v s khng c php

hng dn tin s cho cc nghin cu sinh trong t nht l ba nm.

Taleyarkhan vn li vai tr ca ng l thnh vin ca khoa cp bng trng i hc

Purdue, nhng vi th hng gim st.

Hi thng 7,trng i hc Purdue kt lun rng ng trch dn mt bi bo ca cc

nh nghin cu trong phng th nghim ring ca ng nh th n l mt xc nhn c lp ca

khm ph vin dn ca ng v bt nhit hch.

Strng pht thch ng

Trong qu trnh xem xt a ra phn quyt, ti c ch dn bi nguyn tc

rng s trng pht phi cng khai v tng thch vi nhng h qu nht nh ca s gian ln

trong nghin cu, hiu trng trng Purdue, Randy Woodson, vit trong mt l th gi cho

Taleyarkhan nu ra cc hot ng k lut.


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Woodson thm rng trng i hc s xem xt t cch o c ca Taleyarkhan sau ba

nm na, quyt nhng c c ph hi li t cch thnh vin khoa y hay khng.

Taleyarkhan tin rng quyt nh trn l khng hp l. Cc hnh pht khng cng

bng v i qu xa trong s nghim khc ca h, ng pht biu viphysicsworld.com. ng

ch ra rng mt y ban Purdue trc y min gim ti danh cho ng vo nm 2006, vrng y ban mi ny tha bng cho ng v a s trch nhim trong sai lm nghin cu ca

ng.

ng c chnh tr

Trng i hc bt u kho st mi nht ca n, bao gm nhng lun iu mi

lm bp mo h s nghin cu, ng ni, di p lc chnh tr t pha Quc hi b thc y

bi cc bi bo trn tNature. Sau ht thy, ng tip tc, h thng trng i hc tht bi

thm hi v tm cch thot thn.

Chuyn g s xy ra tip theo ? Taleyarkhan, ngi bt u c n kin dn s

trng i hc, khng hon ton coi nh hot ng lut php. Vi t cch mt thnh

vinkhoa v mt cng dn M, ng ni, ti c quyn yu cu ta n M phn x c bi

thng v s thit hi to ln gy ra cho ti v mt vi ngi khc.

Cc quyn la chn theo php lut

Lut s ca ng, John Lewis, ni cho d cc nh iu hnh Purdue ang nm ly cn

ca vn ny, nhng tin s Taleyarkhan c nhiu quyn la chn trong h thng php lut.

Tuy nhin, Lewis tip tc, sau nhng nm thng vt ln v thnh cng p o chng li

nhng ngi gim pha ng, ng khng th no mun ln su hn trong kha cnh ny. Thay v

vy, ng chn vic tp trung vo ging dy v nghin cu.

Taleyarkhan bin h rng s vic khng gy thit hi cho lng tin vo nghin cu ca

ng. Vn s khng nh hng n nghin cu bt nhit hch, ng tuyn b, sau

cng th hai lun iu chng c g lm vi khoa hc ht v h qu ca s th thch ton

din ny xem xt k hn na v cng c thm gi tr tin cy ca n.Tranh ci 6 nm

Cuc tranh ci bt u nm 2002 khi Taleyarkhan, khi lm vic ti Phng th

nghim quc gia Oak Ridge Tennessee, ng tc gi mt bi bo trn t Science trong

ng bo co bn mt hng ro sng cc m vo mt hn hp cht lng gm benzen v

acetone (Science295 1868). ng khng nh cc bt kh, pht ra cc le sng khi cc sng m
http://www.sciencemag.org/cgi/content/abstract/295/5561/1868http://www.sciencemag.org/cgi/content/abstract/295/5561/1868http://www.sciencemag.org/cgi/content/abstract/295/5561/1868http://www.sciencemag.org/cgi/content/abstract/295/5561/1868http://www.sciencemag.org/cgi/content/abstract/295/5561/1868http://www.sciencemag.org/cgi/content/abstract/295/5561/1868http://www.sciencemag.org/cgi/content/abstract/295/5561/1868


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buc chng n ra v co li, c th t ti nhit v p sut cao n mc trong nhng qu

trnh ny cc phn ng hp nhn c kch hot.

Tuy nhin, mt s nhm nghin cu tht bi trc vic to li nghin cu , trong

khi hai k s Purdue khc Lefteri Tsoukalas and Tatjana Jevremovic phn nn rng

Taleyarkhan c gng ngn cn h cng b nhng kt qu m tnh ca h. Mt kho st nib hi nm ngoi xa cho Taleyarkhan li buc ti , nhng khi cc nh ph bnh cho

rng y ban khng xt n quan im ca h, Purdue bt u mt cuc kho st th hai.

Mc d y ban hon thnh cng vic ca mnh vo thng 4/2008, nhng Purdue khng a

ra bo co mi cho n thng 7 khi Phng Nghin cu Hi qun, n v ti tr cho nghin cu

ca Purdue, ng ph chun n.

Peter Gwynne (physicsworld.com, 28/08/2008)

Knh thin vn tia gamma c t theo tn Fermi

Knh thin vn v tr Tia gamma Din tch rt ln c lp t thnh cng v btu lp bn cc ngun tia gamma trong ton b v tr. S mnh quc t ny c phngln qu o Tri t hi thng 6 va qua cng c t tn li l Knh thin vn v tr Tiagamma Fermi tn vinh nh vt l ngi Italy-M Enrico Fermi.

NASA nh du s kin ny vo hm qua vi vic cng b d liu u tin t vtinh: mt nh chp tia gamma ca ton b bu tri trong 4 ngy bi Knh thin vn Din tchln (LAT) ca knh Fermi. Theo c quan ny, hnh nh c phn gii c th so snh vi nhthu c bi vt tin nhim ca Fermi (i quan st tia gamma Compton) chp trong vi nm.

ang hot ng tt

i quan st nng 4 tn c ch to bi cc nh nghin cu M, Php, c, Italy,

Nht Bn v Thy in. N cn cha GLAST Burst Monitor (GBM) pht hin cc ngunpht nht thi nh cc v bng pht tia gamma v tai la Mt tri.

Ronaldo Belllazzini thuc trng i hc Pisa Italy ngi tham gia vo vicch to LAT pht biu viphysicsworld.comrng chic knh thin vn hot ng nhmong i v c mt vi pht hin mi v cc pulsar, li thin h hot ng v cc v bngpht tia gamma. Nhng kt qu ny s sm c cng b, ng ni.

Tuy nhin, Bellazzini thm rng cc nh thin vn vt l s phi ch thm cht natrc khi Fermi bt u mang li d liu c ngha v mt trong nhng mc tiu ch yu ca


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n lm sng t bn cht ca vt cht ti. Cc ht vt cht ti nht nh, gi tn l Cc htnng tng tc yu, hay WIMP, c th phn hy to ra cc tia gamma, chng c th biuhin l nhng tn hiu tia gamma nh xu t qung vt cht ti bao quanh cc thin h. Smt khong mt nm tm hiu tinh vi ca thit b v thu thp dliu, Bellazzini ni.

Bc nh chp ton b bu tri nyh l s pht x tia gamma sng chi trong mt phng caDi Ngn h ( gia), cc pulsar sng v cc l en siu trng.

Nim hnh din Pisa

Bellazzini nht nh hi lng vi tn gi mi ca chic knh thin vn v Fermi l mtsinh vin ti trng i hc Pisa. Fermi lm vic tin tuyn ca ngnh vt l ht v thinvn vt l, ng ni, nhc ti nghin cu tin phong ca Fermi v s gia tc ca cc tia v tr.

Sinh Rome vo ngy 29/09/1901, Fermi ginh c gii thng Nobel Vt l nm1938 cho nghin cu ca ng v cc phn ng ht nhn. Cng nm , ng ri Italy sang M, ng gi vai tr quan trng trong D n Manhattan. Fermi mt ti Chicago vo ngy28/11/1954.



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Cc nguyn t lnh n trng nh giao lng cao tc

Cc nh vt l c va to ra c nhng v n ngon mc, hnh dng giao l trongmt cht kh gm cc nguyn t cc lnh b by bi t trng. Hnh nh giao l c hnhthnh bi s iu chnh kho lo cc tng tc t gia cc nguyn t, to thnh mt ha cBose-Einstein (BEC) v v th tt c trong mt trng thi lng t nh nhau. Mc d ccbosenovas nh th c trng thy trc y, nhng trc y ch ng lun lun c hnhdng ging nhau theo mi hng.

Bosenovas c to ra ln u tin cch nay khong chng 10 nm bng cch iuchnh cng t trng gia cc nguyn t trong mt BEC sao cho cc lc Van der Waalstm ngn gia cc nguyn t l lc ht, thay v y. Vic ny lm cho BEC co li trn chnhn ging ht nh mt ngi sao hp hi. Sau n bng n ging nh nhng sao siu mi nhxu v nm ra nhiu trong s cc nguyn t thnh phn ca n.

Cc nh vt l tin rng v n xy ra khi cc nguyn t gn nhau cho cc tng tctm ngn nh hng n cc nhm ba nguyn t (tng tc ba vt) thay v ch hai nguynt. Cho n nay, th lc ht gia cc nguyn t l ng hng, ngha l cc v n bn cc

nguyn t ra mi pha u nh nhau.

Lot nh lin tip ca BEC ang gin n trong nhng khong thi gian 0,1 ms cho thy s xut hin ca hnh nhgiao l t mt BEC n tung (hnh tn cng bn tri). Cc nh pha trn l BEC thc v pha di l m phngmy tnh.

Cc hng u tin

Tuy nhin, nay Tilman Pfau v cc ng s ti trng i hc Stuttgart to ra cbosenovas u tin trong lc ht gia cc nguyn t l c tnh lng cc v do phthuc vo s nh hng tng i ca cc nguyn t. iu ny gy ra cc v n hnh giao lm theo i nghin cu l n phn nh s i xng c bn ca cc lc ht (Phys Rev Lett101 080401).

i nghin cu s dng mt BEC cc nguyn t chromium-52, chng c momentlngcc t ln. Lc t gia cc nguyn t l lc ht v thng yu hn nhiu so vi cc lcvan der Waals. Tuy nhin, i nghin cu iu chnh t trng sao cho cc lc van derWaals gn bng khng, cho php lc t gia cc nguyn t chim u th.

Theo BEC, vic ny lm cho BEC co li cho n khi cc nguyn t gn nhau chocc tng tc ba vt gy ra mt v n. Trong qu trnh ny, mt s nguyn t b nm ra khiBEC, trong khi BEC cn li gin ra pha ngoi vi hnh nh giao l c trng. Mt hnh nh
http://link.aps.org/abstract/PRL/v101/e080401http://link.aps.org/abstract/PRL/v101/e080401http://link.aps.org/abstract/PRL/v101/e080401http://link.aps.org/abstract/PRL/v101/e080401http://link.aps.org/abstract/PRL/v101/e080401http://link.aps.org/abstract/PRL/v101/e080401http://link.aps.org/abstract/PRL/v101/e080401http://link.aps.org/abstract/PRL/v101/e080401


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nh th c trng i i vi mt BEC ang gin n vi cc tng tc lng cc trong s cmt ca t trng, theo Pfau.

Mt kiu co linh nhng

V s co li b chi phi bi cc tng tc t yu hn nhiu, cho nn n du dng hnnhiu so vi s co li gy ra bi cc tng tc van der Waals, theo Pfau. ng ni, vic nykhin d hn cho Masahito v cc ng s ti trng i hc Tokyo s dng cc l thuyt

BEC hin nay m t qu trnh bosenovas th t ra kh khn trong qu kh.Cc m phng my tnh do i Ueda thc hin cho thy s co li BEC lin quan n

s hnh thnh hai vng xoy quay theo hng ngc nhau. Cc nh vt l hin ang tptrung xem xt h c th to ra cc xoy bn hay khng bng cch iu chnh cc tng tc yvan der Waals tr li trc khi BEC bng n.

Pfau tin rng s nhn thc su sc v cch thc to ra v iu khin BEC chromium-52c th mt ngy no c lin quan n cng ngh. Chromium c s dng trong mt scng ngh nano v BEC chromium-52 c th hnh thnh nn c s ca laser nguyn t cth cho lng nhng lng ht sc nh chromium-52 n phn gii khng gian cc k cao.

M phng t hc

mc c bn hn, cc tng tc lng cc trong BEC ging nh cc tng tc tmthy trong cc cht liut v Pfau tin rng h c th s dng lm mt b m phng lng t nghin cu t hc.

Dave DeMille thuc trng i hc Harvard tn thnh kin trn. ng pht biu viphysicsworld.comrng BEC c th cho php cc nh vt l to ra mt lin kt mi, su scgia cc th nghim nguyn t cc lnh v nhiu h t hp dn trong cc cht liu thc t.


B lp lng t c chng minh

Mt i cc nh vt l quc t va tin thm mt bcquan trng trn con ngdn n s truyn thng lng t ton cu bi vic chng minh c nguyn tc c bn camt b lp lng t. Bc t ph, nh du ln u tin hai m my nguyn t b ri t xa,c th mt ngy no c s dng chng li s phn hy trong cc tn hiu lng t.

Truyn thng lng t mang li mt phng tin truyn ti thng tin v c bn l anton. N yu cu hai nhm i tng b ri trn mt knh dn lng t, trn mt khagii m thng tin m ha c th c thit lp. V kha ny tr nn b hng ngay khi n b s


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dng ln u tin, nn ngi nhn d kin lun lun c th bit c kha b chn libi mt k nghe trm hay cha.

Mc d truyn thng lng t c s dng trn nhng khong cch 100 km hocngn y, nhng tht kh to ra s ri trn nhng khong cch ln hn do s suy gim tn hiu.Trong truyn thng c in, phng thc n gin l khuch i tn hiu mt cch tun hon,nhng vic ny khng th thc hin i vi cc kha lng t v nh l v sinh ngm cm

mt tn hiu lng t b sao chp.To ra s ri

Cu tr li l b lp lng t - v nay Jian-Wei Pan, Yu-Ao Chen v cc ng s nt trng i hc Heidelberg, trng i hc Khoa hc v Cng ngh Trung Hoa v trngi hc Cng ngh Vienna chng minh c mt phin bn th ca mt dng c nh th. tng l knh dn lng t c chia thnh cc on, mi on d b ri hn. Mt khi ccon b ri ring l, khi chng c th ri cng vi nhau thng qua qu trnh ging nhau.

Pan v cc ng s chng t c lm th no lm ri mt trong cc on. H btu vi hai m my cc lnh gm cc nguyn t rubidium, mi m h lm cho ri vi mt photon c thn. Hai photon sau c gi v pha nhau qua knh si quang. Ti chnh

gia, cc photon i qua mt b tch chm tia, v cui cng cc nh nghin cu tin hnh mtphp o trn chng lm ri cc m my nguyn t (Nature454 1098).

i nghin cu pht biu trong bi bo co ca mnh ng trn tNaturerng h chiu khin c s ri ca mt knh dn si quang di 300 m, n b hn ch bi thi giansng 10 s ca m my nguyn t. Tuy nhin, Chen ni vi physicsworld.com rng h tng thi gian sng ca m my nguyn t ln 1 ms, nh m ra cnh ca a n mtknh dn lng t di 100 km.

Cc nh nghin cu hin ang c gng tng hiu sut t 10% ln n v h c thghp i mt vi on ri li vi nhau.



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Dng c nhc th lu tr d liu bng nhit

Nhit t lu c xem l v dng hay thm ch l c hi trong cc mch in t.

Nhng mt s nh nghin cu cho rng ngi ta c th ch to cc my tnh x l cc phonon

cc xung dao ng mang nhit thay cho cc electron truyn thng.

Cc nh vt l Singapore v Trung Quc va tin thm mt bc v hng in ton

nhit hay phononics nh th bng vic ngh ra mt m hnh cho lu tr thng tin nhit. Mc

d c cu ca h cha c kim tra v mt thc nghim, nhng cc nh nghin cu khng

nh cc bit thng tin c th c ra m khng ph hng d liu lu tr

(arXiv:0808.3311v1).

Trong mt mch in t thng thng, cc trng thi 0 v 1 thng c xc nh

bi cc in p chun. Tuy nhin, trong cc mch nhit, cc trng thi c xc nh bi

hai nhit c on. Theo nh lut hai nhit ng lc hc, mt s gim nhit a n

mt dng nhit chy t mt vng nng sang mt vng lnh. Ni chung, s gim nhit cng

ln th dng nhit cng ln, n c gi l nhit tr vi phn dng.

Cc dng nhit ny c mang bi cc phonon, chng kh iu khin v chng l cc

b nng lng khng c in tch v do khng th iu khin bng in t trng.

Cc b nh cn thiu

Cc nh nghin cu hin lm ch c vic ch to mt diode nhit v thm ch cnchng minh c rng c th ch to cc transistor v cng l gic nhit tt c cc linh kin

chun dng cho cc dng c nhitchc nng. Nhng cn c b nh lu tr tn hiu ra sau

khi tin hnh cc ton t l gic.

Nay, Baowen Li n t trng i hc quc gia Singapore v Lei Wangn t trng

i hc Renmin Bc Kinh, Trung Quc, va ngh ra c mt m hnh l thuyt cho b nh

nhit nh th. M hnh ca h a mt yu t ch o vo trong cc cng l gic nhit cho

n nay cha c chng minh v mt thc nghim bng cch to ra mt nhit tr vi phn

m (NDTR). NDTR ngha l mt s gim nhit ln dn n mt dng nhit nh v mt s

gim nhit nh dn n mt dng nhit ln.

Trong m hnh b nh nhit ca h, Li v Wang xt hai b nhit, gi mt nhit

khng i, mi b nm ti u ca mt ci que. u kia, u t do ca que khng tip xc vi

nhau, tuy th vn ghp nh vi nhau sao cho c mt NDTR gia chng. Thnh phn cui cng

ca m hnh ca h l mt ht nm ti u ca mt que, gn khe h gia cp que.
http://arxiv.org/abs/0808.3311http://arxiv.org/abs/0808.3311http://arxiv.org/abs/0808.3311http://arxiv.org/abs/0808.3311


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c v ghi

Li v Wang sau xem xt ci xy ra khi mt vt ni vi b nhit ring ca n lm

lnh ht ny xung di mt nhit c on, t tn l 0. y l ci h gi l qu trnh

ghi.

c ra nhit ca ht, h s dng mt vt khc t tn l b c t

mt nhit na chng gia 0 v mt nhit khc, c xc nh l 1. Ht khi nng

ln khi b c ny mang ti tip xc vi n, gy ra mt dng nhit ln chy t ht, xung que

n b nhit.

Tuy nhin, ch c mt dng nhit nh trong que kia khi n ni kt thng qua NDTR.

Ni cch khc, dng nhit trong que th hai tr i dng trong que th nht l m. Dng ny

mang nhit ra khi ht, lm lnh xung ti 0. Khi b c tip xc vi ht, b c cng

chuyn sang trng thi 0. Ni cch khc, n c ra trng thi 0 ban u ca ht.

Theo kiu tng t, Li v Wang cn ch ra c rng nu ht c chun b trong

trng thi 1 nng hn b c, th n cng c th c c ra m trng thi khng b ph

hng.

Dliu khng th no lu tr trong mt thi gian di trc khi nhit r r ra ngoi. Li

tnh ton c b nh nhit s phi c lm ti mi 100 s nu nh cc que ch to t ng

nano carbon. Gi tr nhanh hn nhiu so vi cc DRAM in t s dng trong cc my vi tnh

hin nay yu cu lmti mi 64 ms.

Khng truy hi tc thi

Mt kh khn na vi b nh nhit l thi gian truy xut chm. S chnh lch ln l

gia tc ca sng in t v phonon, Li pht biu vi physicsworld.com. Cc phonon

truyn i tc khong 1000 ms-1, hng trm nghn ln chm hn cc sng in t. Tc

ca b nh nhit l mt vn ch yu yu cu c thm nhng nghin cu khc na, ng

ni. Mt khi v nu nh NDTR c nhn ra bng thc nghim, Li v cc ng s chc chn

rng b nh nhit s l bc tip theo hng ti cc my vi tnh nhit.

Michael Banks (physicsworld.com, 29/08/2008)

Bản tin Vật lí tháng 8/2008 (hiepkhachquay)

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Transcript of Bản tin Vật lí tháng 8/2008 (hiepkhachquay)