The Strange Universe
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Transcript of The Strange Universe
The Strange UniverseThe Strange Universe
Sanjay K. GhoshDepartment of Physics
Bose InstituteKolkata
Early EffortsEarliest astronomical records : 2000 - 1500 BC
Mesopotamian priests : systematic astronomical records Sumarians, Babylonians, and Egyptians develop astronomy
Greece School : 600BC - 200AD Anaximander, Pythagores, Aristotle, Hipparchus, Ptolmey Earth is the center of Universe
Indian Contribution : 500 – 600 AD
Aryabhatta: Sun is the centre of the Solar System. Varahamihira : earth attract bodies.
Arab School : 850 - 1200AD Al-Battani, Al-Sufi, Al-Biruni, Arzachel
Andromeda Galaxy, idea of elliptical orbits for planets, Appearance of Milky way
Modern Astronomy 1543ADPolish priest, Nicholas Copernicus: Sun centered solar system (Revival of the idea of Aristarchus of Samos 200BC) 1572ADDanish Astronomer,Tycho Brahe – Last naked-eye astronomer :exploding star- NOVA, Comet orbit
Spectacle maker Hans Lippershey (1570 -1619): Assembled first telescope
1610ADItalian, Galileo Galilei : Use of telescope1620AD John Kepler : Kepler’s Law
More and better observational data
Distance measurement known from 1700
Works only for nearby star
Need for Standard Candles to measure larger distances
Standard Candles : Cepheid Variables
giant yellow star pulsing regularly by expanding and contracting
fairly tight correlation between period of variability and absolute stellar luminosity (total light per sec)
Luminosity related to apparent brightness (light received/area/sec.) and distance (from parallax method)
Period – Luminosity Law
(Henrietta Swan Leavittin 1912)
A photograph such as this shows bright stars as larger disks than fainter stars
Harvard College Observatory
Edward Charles Pickering Director of HCO (1877-1919)
"Pickering's Harem" or, Harvard Computers.
The synthesis of helium At temperatures above 1010 K, any deuteron formed from a neutron—proton collision was quickly disrupted by a collision because the thermal energies involved often exceeded the 2.2 MeV binding energy of the deuteron. The only nuclei existing at these temperatures were single protons and neutrons.
In normal circumstances a neutron beta decays with a mean life of about 15 minutes to a proton, an electron and an anti-neutrino,
At high temperature and density, neutrons can be transformed to protons, and protons can be transformed to neutrons in collisions involving thermal neutrinos, anti-neutrinos,electrons & positrons
Heavier neutron – more energy needed for creation –
no. of neutron < no.of proton
proton &neutron
of difference massMeV3.1 m
n and p ratio decreased with decreasing T – expanding Universe
Ratio became about 1/5 just below 1010 K – further decrease due neutron decay
After a few minutes, when n decay had reduced the n-p ratio to about 1/7, the universe was cool enough for a sequence of two-body reactions - bound states of n and p. At about 109 K deuteron nuclei began to be present in significant amounts as n-p radiative capture, n + p d + , competed successfully with deuteron photodisintegration, + d n + p. Capture of neutrons and protons by deuterons led to the formation of tritons and helium-3.
These nuclei in turn captured p and n to form helium-4. Since helium-4 is by far the most stable nucleus in this region of the periodic table, nearly all the neutrons that existed when the temperature was 109 K were converted into helium-4. Moreover, the absence of stable nuclei with mass 5 and 8 prevented the formation of more massive nuclei, apart from small amounts of lithium-7.
• Problem with BBN • Input for BBN – baryon to photon ratio• 5.89 x 10-10 < η < 6.39 x 10-10 baryons/photon
• BBN provided the raw material for the first stars
• Gravitational Contraction
Gravity is the driving force behind stellar evolution. Most importantly it leads
to the compression of matter and thence to the formation of stars. It leads to the conditions where nuclear forces play a constructive role in thermonuclear fusion. The transformation of hydrogen to helium in the hot compressed centres of stars is often followed by a further compression and the transformation of helium into more massive elements such as carbon, oxygen and iron, the star dust out of which we are all made.
Burning Chain H He C O Ne Si Fe
Process Fuel Product Temperature (K)
Minimum Mass M
H Burning H He 10-30 X 106 0.1
He Burning He C, O 2 X 108 1
C Burning C O, Ne, Na, Mg
8 X 108 1.4
Ne Burning Ne O, Mg 1.5 X 109 5
O Burning O Si, S, Kr, Ca 2 X 109 10
Si Burning Si Fe 3 X 109 20
Arthur Eddington (1924) : Mass-Luminosity relationship
Outward radiation pressure = inward gravity
Fritz Zwicky (1933) :
Measured velocity of eight galaxies in COMA cluster
Mass/Luminosity is much larger than expected from mass-luminosity relation
Vera Rubin (1975) most stars in spiral galaxy orbit roughly at the same speed
Presence of DARK MATTER in the galaxies
The average speed of galaxies within a cluster depends on the total mass of the cluster, since each galaxy is attracted by the gravity of all the others.
From the observed speeds of galaxies moving within the Coma cluster, Zwicky calculated its total mass. -added up all the light from the galaxies in the cluster and used it to calculate the mass in the form of luminous stars. - mass of the cluster based on the speed of its galaxies was about ten times more than the mass of the cluster based on its total light output. - Coma cluster must contain an enormous quantity of unseen matter, with enough gravity to keep the rapidly moving galaxies from flying apart
- Dark Matter
r
GMv
22
• Gravitational lensing : one or more images of a distant source
Gravitational Microlensing
Darkmatter: What are they
• DEAD stars ????
• Primordial black holes ???
• Weakly Interacting massive particles???
Hubble’s Law (1929) : Expanding Universe
- Cepheid variables – Leavittin’s relation
• Recessional Velocity = Hubble's constant times distance
• V = Ho D where
• V is the observed velocity of the galaxy away from us, usually in km/sec
• H is Hubble's "constant", in km/sec/Mpc
• D is the distance to the galaxy in Mpc
V is related to red shift
Doppler Effect
Doppler Effect
Gravitational Red Shift:
A heavy object is denoted by a deformation of space represented by the funnel. As light leaves the vicinity of this object it is shifted towards the red: for a sufficiently compact and massive object a blue laser on the surface will be seen as red in outer space.
Comological red shift
Going the distance
Although Cepheid variable stars have proved extremely valuable as standard candles in astronomy for many years, they are not bright enough to be used at high redshifts. However, astronomers have found a very special type of supernova to take their place.
The light emitted by stars and gas in distant galaxies has been stretched to longer wavelengths during its journey to Earth. This shift in wavelength is given by the redshift, z = (λobs – λ0)/λ0, where λobs is the wavelength we see on Earth and λ0 is the wavelength of the emitted light.
Prime methods for measuring extragalactic distances - “standard candles” such as Cepheid variable stars.
The distance to a Cepheid - first measure its period to obtain the luminosity
-then compare this with the observed intensity to calculate the distance.
-Thus, redshifts and distances to objects moving in the “Hubble flow” (the region beyond the gravitational influence of our local group of galaxies) have been charted, revealing the Hubble law: d = (cz/H0), where c is the speed of light and H0 = 72 ± 8 km s-1 per megaparsec (Mpc) is the Hubble constant (1 Mpc is equal to 3.26 million light-years).
Can one explore farther : New Candles
Type IA supernova
Binary system of white dwarf and red giant
accretion onto the white dwarf
reaches Chandrasekhar Limit
Gigantic thermonuclear reaction
Mid 1990
High z Supernova search
(Mt. Stromlo and Siding spring
Observatory,Australia)
International Supernova Cosmology
Project (LABL, USA)
1998 - Recorded 100 or so supernova
Observations of supernovae can be used to chart the history of the cosmic expansion. (a) The distance to a type 1a supernova is obtained from its luminosity, which is calibrated by its light curve and spectrum, and its observed intensity.
(b) Meanwhile, the expansion of the universe shifts features in the supernova spectrum to longer wavelengths by a factor characterized by the redshift.
(c) By plotting distance versus redshift for a large number of supernovae, we can chart how the universe has expanded over time.
orange circles -data points along with the theoretical prediction:
a universe with 30% matter and 70% cosmological constant (blue).
universe with 30% matter and spatial curvature (red dashed)
100% matter (purple dashed).
Green- no acceleration or deceleration
(Rainer Sachs & Art Wolfe)
Integrated Sachs-Wolfe (ISW) Effect:Integrated Sachs-Wolfe (ISW) Effect:Gravitational potential wells of dense and overdense
regions in the universe have been stretched and made shallower over time
Influence of repulsive gravity (or acceleration)
• The Sloan Digital Sky Survey (SDSS) identifies Galaxy Concentrations and determines their positions on the sky.
• The Wilkinson Microwave Anisotropy Probe (WMAP) measures the angular pattern of energies of the Cosmic Microwave Background Radiation (CMBR) [reds,yellows, greens, blues, purples, in order of increasing energy].
Position of the peak in this spectrum depends on the geometry of the universe. Recent observations confirm that the peak occurs at the position predicted for a flat universe (blue). In an open universe the peak would be to the left (red), and in a closed universe it would be on the right (green).
Expansion of the Universe is Expansion of the Universe is acceleratingaccelerating
Evidence of Dark Energy
• WMAP• (Wilkinson Microwave
Anisotropy Probe)
• Universe is 13.7 billion years old (±1%) • First stars ignited 200 million years after
the Big Bang
• Content of the Universe: 4% Atoms, 23% Cold Dark Matter, 73% Dark Energy
• Expansion rate (Hubble constant): H0= 71 km/sec/Mpc (±5%)
Evolution of the conceptEinstein : Cosmological Constant
General theory of relativity (1916)
Universe either expands or contracts
For Static Universe
Cosmological Constant
Hubble’s Theory (1929) Expanding Universe
Cosmological Constant dropped
Attempts for revival 1960 : Vacuum energy of particles and
fields should generate 1980 : Theory of Inflation
Early Universe goes through brief period of accelerated exponential expansion
-ve pressure drives the expansion
Inflaton
Candidates : ( pDark = w eDark )
Cosmological Constant : Static (w = -1)
Quintessence : Dynamic (w > -1)
Other Vacuum Energy (w < -1)
Modification of GTR
Dark Energy
CDM : Dust like equation of state Pressure p=0 Energy density e > 0
Dark energy : p=w e; w < 0 (Ideally w= -1)
+ve energy -ve pressure
• Dark Energy
(a) emits no light
(b) it has large –ve pressure
(c) does not show its presence in galaxies
and cluster of galaxies, it must be smoothly
distributed
e c~ 10-47 GeV4 , So for DE ~ 0.7,
eDE ~ 10-48 GeV4 Natural Units
Natural Explanation : Vacuum energy density
with correct equation of state
Difficulties : higher energy scales
Planck era : ~ 1077 GeV4
GUT : ~ 1064 GeV4
Electroweak : ~ 108 GeV4
QCD : ~ 10-4 GeV4
Puzzle Why eDE is so small ???
Dark-Matter & Dark-Energy
Coloured Gluon exchange between coloured quarks
Overlapping nucleons
First order phase transition
T> Tc : coloured quarks and gluons in thermal equilibrium At Tc : bubbles of hadronic phase
grow in size and form an infinite chain of
connected bubbles
universe turns over to hadronic phase
in hadronic phase quark phase gets trapped in
large bubbles
Trapped false vacuum domains (TFVD) evolve to
Strange Quark Nugget (SQN)
For Stable SQNs A > 1044
Characteristics of SQN• large mass & non-relativistic
• large mutual separation ~ 300m at Temperature of 100Mev
• Discrete bodies in the background radiation fluid
• radiation pressure & Gravitational Potential due to other SQNs
Thermal and gravitational motion
• Density of SQNs decrease as t-3/2
mutual separation increases as t1/2
• mutual gravitational pull decreases as t-1
Force due to radiation decreases as T4 or t-2
gravitation will overcome radiation pressure
No. of MACHO TODAY
Total No. of MACHO ~ 1022-23
1013-14 MACHO in Milky Way Halo
T> Tc : coloured quarks and gluons in thermal equilibrium At Tc : bubbles of hadronic phase
grow in size and form an infinite chain of
connected bubbles
universe turns over to hadronic phase
in hadronic phase quark phase gets trapped in
large bubbles
Trapped domains evolve to SQN
What did we miss ???
Role of colour Charge
Assumption : Many body system
Colour is averaged
Only statistical degeneracy
Too Simplified ?????
Quantum Entanglement
• Typical quantum phenomena
Particles which are far apart seem to be influencing each other
Condition : Particles must have interacted with each other earlier
Measurement on one immediately specifies the other
Interacting particles always entangled
• Before P.T. Universe singlet
Wave functions of coloured objects entangled
Universe characterized by perturbative vacuum
During P.T. local colour neutral hadrons
Gradual decoherence of entangled wave functions
Proportionate reduction of vacuum energy
Provides latent heat of the transition
In Quantum mechanical sense
completion of quark-hadron P.T.
Complete decoherence of colour wave function
Entire vacuum energy disappear
Perturbative vacuum is replaced by non-perturbative one
Does that really happen ????
Stable nuggets
Colour neutral
All have integer baryon number
At the moment of formation quark number multiples of 3
Statistical system some residual colour
For colour neutrality : one or two residual quarks
End of cosmic quark-hadron phase transition
few coloured quarks separated in space
Colour wave functions are still entangled
Incomplete decoherence
Residual perturbative vacuum energy
Dark Energy ~ 10-48 GeV4
DE Constant
Matter density decreases as R-3
DE is dominant at late times
Dark-Matter & Dark-Energy
Strange Quark Matter & Orphan quarks
Consequence of Early Universe
Quark-Hadron Phase Transition
The Strange Universe
Collaborators
1. A. Bhattacharyya (Scottish Church College, Kolkata)
2. S. Banerjee (St. Xaviers College, Kolkata)
3. S. Raha (Bose Institute, Kolkata)
4. E. Ilgenfritz (RCNP, Osaka)
5. B. Sinha (VECC, Kolkata)
6. E. Takasugi (Osaka University, Osaka)
7. H. Toki (RCNP, Osaka)
Natural Units
Velocity of light c = = 1
Planck’s Constant
Temperature Energy Mass = MeV (106 eV)
Length Time = fm (10-15 m)
sec103 8 m
m103sec.1 8
J)106.1eV1(
1
sec.eV106.6
sec.J1005.1
19
16
34
Natural Units
Boltzman Constant k =1
Me = 0.511 MeV = 9.1 10-31 Kg
1 MeV (Temperature) = 1010 0K
1 M (Solar Mass) = 2 1030 Kg
back
No. of MACHO today
• T ~30K t ~ 4 X 1017 seconds
• Total baryons today from η = 10-10
• With CDM~ 0.3 ; baryon ~ 0.01
• Baryons in CDM = CDM / baryon X visible baryons
1.6 X 1079
• No. of MACHO = baryons in CDM / baryons in MACHO ~ 1022-23
• Milky Way visible mass ~ 1.6 X 1011M
2 X1068 baryons
2 X 10-9 of visible baryons inside
horizon
• Scaling 1013-14 MACHOs in Milky Way
Halo.
• Estimate : Bag model
• Bag pressure B difference between two vacuum
Beginning of P.T. vacuum energy B
This decreases with increasing decoherence
What will be Measure of entanglement
Measure : Volume Fraction of coloured degrees of freedom
Initially : fraction is unity complete entanglement
Finally : Small entanglement tiny but non-zero colour fraction
Amount of perturbative vacuum energy at any time= B X instantaneous colour fraction volume
Order of magnitude estimateFor percolating system : characteristic
critical fraction ~ 0.3 for high T phase Volume fraction in the form of TFVD
~ 0.3 Most likely length scale of TFVD ~ few cm
So at percolation time of 100 s No. of TFVD ~ Nq,O ~ 1018-20
Inter-TFVD separation ~ 0.01 cm
Order of magnitude estimate
Effective radius of orphan quark
qq= 1/9 pp ; pp ~ 20mb
rq,O=10-14 cm
Number of orphan quarks = Number of TFVD Nq,O ~ 1018-20
Coloured Volume fraction = Nq,O X (vq,O/VH) ~ 10-42 - 10-44
Residual vacuum energy =
Coloured Volume fraction X B
~ 10-44 X B
GeV)4
DE ~ 0.7
Alternative Prescription Problem with Inter-quark potential at large r Usual way- phenomenological string model
for quark-antiquark Richardson’s potential :
Linear potential in the large r limit
Our system : Dilute many body system of quarks (only)
Density dependent effective quark mass (DDQM) model
DDQM model mq ~ 1/nq
s = 1/log(1 + Q4/4)
Familiar perturbative form for large Q2.
V(r) = { (r)3 – 12/(r) }
For large r, V(r) ~ r3
Estimation of inter quark potential
nq,O Nq,O/VH
= (3/4) Nq,O / R3H
r = (3 nq,O/4)1/3
= RH / N1/3q,O
Potential energy density for inter-quark interaction is
V = nq,O V(r)/2 ~ (3/8) 4
Constant Independent of time
How to fix :
for hadronic bag ~ 100 MeV Our case appropriate length scale size of the smallest TFVD Stable Nuggets baryon density 1038 cm-3
Size ~ several cm Baryon density in Universe ~ 1030 cm-3 For TFVD with density 1030 cm-3 Size ~ 0.01cm
Other possible length scale Inter TFVD separation is of same order
~ 10-12 GeV Dark Energy ~ 10-48 GeV4