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Expansion of the Universe
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Title: Expansion of the Universe - Standard Big Bang Model
Authors: Matts Roos

After a brief introduction to the sixteenth and seventeenth century views of the Universe and the nineteenth century paradox of Olbers, we start the history of the cosmic expansion with Hubble's epochal discovery of the recession velocities of spiral galaxies. By then Einstein's theories of relativity were well known, but no suitable metric was known. Prior to introducing General Relativity we embark on a non-chronological derivation of the Robertson-Walker metric directly from Special Relativity and the Minkowski metric endowed with a Gaussian curvature. This permits the definition of all relativistic distance measures needed in observational astronomy. Only thereafter do we come to General Relativity, and describe some of its consequences: gravitational lensing, black holes, various tests, and the cornerstone of the standard Big Bang model, the Friedmann-Lemaitre equations. Going backwards in time towards Big Bang we first have to trace the thermal history, and then understand the needs for a cosmic inflation and its predictions. The knowledge of the Big Bang model is based notably on observations of the Cosmic Microwave Background Radiation, large scale structures, and the redshifts of distant supernovae. They tell us that gravitating matter is dominated by a dark and dissipationless component of unknown composition, and that the observable part of the Universe exhibits an accelerated expansion representing a fraction of the energy even larger than gravitating matter.

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RE: Big Bang
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The history of cosmology the study of the Universe for the last five hundred years is often portrayed as a clash between science on the one hand, and the cold hand of religious dogma on the other.
Part of this is rooted in fact the Catholic Church of the Counter-Reformation for instance was suspicious of intellectual innovation and experiment, with its harsher elements longing for the certainties of the age before Martin Luther and the Protestant Reformation. The desire to make the Universe fit into a pre-ordained and orderly scheme that needed no correction reached its infamous, idiotic height as the Dominican Order and the Inquisition persecuted Galileo for his accurate insistence that the Earth orbited the Sun. Galileo's fate at the hands of Pope Urban VIII was not inevitable - but for various historical contingencies, the Church might have not have set its face against him. But this is far from the only episode of a reactionary Church choosing to block knowledge and progress instead of contributing towards it.

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Quark-gluon plasma
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What do sand and quarks have in common? The answer, according to physicists in the US, is that they both behave like liquids under certain circumstances. When Sidney Nagel and colleagues at University of Chicago fired jets of sand-like granular materials at solid targets, some of the resulting spray patterns were very similar to what has been seen when heavy nuclei collide to produce a quark-gluon plasma. The discovery could shed light on why such a plasma appears to behave like a liquid rather than a gas something that has puzzled physicists since the behaviour was first seen in 2005.

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Title: CPT violations in Astrophysics and Cosmology
Authors: G. Auriemma

In this paper it is given a brief review of the current limits on the magnitude of CPT and Lorentz Invariance violations, currently predicted in connection with quantum gravity and string/M-theory, that can be derived from astrophysical and cosmological data. Even if not completely unambiguous, these observational tests of fundamental physics are complementary to the ones obtained by accelerator experiments and by ground or space based direct experiments, because potentially can access very high energies and large distances.

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Title: Axion Inflation in Type II String Theory
Authors: Thomas W. Grimm

Inflationary models driven by a large number of axion fields are discussed in the context of type IIB compactifications with N=1 supersymmetry. The inflatons arise as the scalar modes of the R-R two-forms evaluated on vanishing two-cycles in the compact geometry. The vanishing cycles are resolved by small two-volumes or NS-NS B-fields which sit together with the inflatons in the same supermultiplets. String world-sheets wrapping the vanishing cycles correct the metric of the R-R inflatons. They can help to generate kinetic terms close to the Planck scale and a mass hierarchy between the axions and their non-axionic partners during inflation. At small string coupling, D-brane corrections are subleading in the metric of the R-R inflatons. However, an axion potential can be generated by D1 instantons or gaugino condensates on D5 branes. Models with sufficiently large number of axions admit regions of chaotic inflation which can stretch over the whole axion field range for potentials from gaugino condensates. These models could allow for a possibly detectable amount of gravitational waves with tensor to scalar ratio as high as r<0.14.

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Time = 10-6 seconds; Temp = 3x1013
The temperature is too cool for Protons to get broken down to energy. Photon radiation cannot undergo matter-antimatter particle transformation using massive particles like protons and neutrons.
In 1964it was found that the laws of nature were not completely symmetric with respect to matter and antimatter. An ephemeral particle known as K-mesons, or kaons, violated the so-called charge-parity (CP) symmetry
There was a discrepancy in the decay between kaons and anti-kaons.
In 1967, Andrei Sakharov wrote his landmark paper; "Violation of CP Invariance, C Asymmetry, and Baryon Asymmetry of the Universe" took the dynamic generation of the baryon asymmetry of the universe seriously. He laid out the basic principles needed to understand this asymmetry and how it led to the dominance of matter in the universe. Its a modification of the Standard Model called supersymmetry; nature should show a new symmetry at extremely high energies. This paper, though slightly cryptic, showed that the violation of CP symmetry is just one of three conditions that must be satisfied to explain how an imbalance arose between matter and antimatter.
Violation of the "conservation of baryon number" law. If baryon number is conserved in all reactions, then the present baryon asymmetry can only reflect asymmetric initial conditions, and we are back to the first case in the previous list.
C and CP violation. Even in the presence of baryon-violating reactions, without a preference for matter over antimatter the baryon-violation will take place at the same rate in both directions, leaving only very tiny statistical excess.
Thermodynamic Nonequilibrium. CPT guarantees equal masses for baryons and antibaryons. The early universe cannot always have been in thermal equilibrium. Therefore chemical equilibrium would drive the necessary reactions to correct for any developing baryon asymmetry.

Supersymmetry allows stronger CP violation than the Standard Model, and predicts a whole new class of subatomic particles and new ways for CP violation to come about. It is capable of simultaneously satisfying all three conditions and generating the right magnitude of the asymmetry.

Observations of decay of kaons showed that there was a `direction` involved in the reactions, CP-violation (that's "charge conjugation" and "parity"), although small there was a preference or `chirality` in the experiments. But the violation of CP symmetry allowed by the Standard Model is too small to account for the amount of matter observed in the universe

"The Standard Model has been a source of frustration because it can't fully explain where the asymmetry between matter and antimatter comes from. If these new experiments support the Standard Model, then we will still have a puzzle,"

The origin of large-scale structure, the matter/antimatter asymmetry and the dark matter of the universe may be due to Cosmic strings Why are we Matter dominated today?:
The Universe began that way. But it doesn't work because of "inflation" theories, which dilute any initial abundance. Baryogenesis occurred around the Grand Unified (GUT) scale. Long thought to be the only viable candidate, GUT's generically have baryon-violating reactions, such as proton decay (with half-life of 1032years. This is not observed). Also neutrinos have mass and vast numbers of magnetic monopoles were created.

A major theoretical problem, in fact, is that there may be too much B-violation in the Standard Model,
Some GUTs predict that neutrinos have a very small mass, perhaps 0.001% of the electron mass. Even with this small mass they could have promoted galaxy formation. They can start clumping by gravity well before other particles can. Atoms would have gathered around neutrino clumps. Massive neutrinos may form invisible matter, the Dark matter, sought after.

Time = 10-? Seconds; Temp = 3x109
Electrons condense out,

When the universe had cooled to a temperature of 6 109 K and the electron-positron production and annihilation process stopped. Also the number of neutrons stopped increasing by the proton-electron fusion process. The number of neutrons was fixed at a ratio of 1 neutron for every 5 protons. There was a very slight excess of ordinary matter over antimatter (by about 1 part in 109).
All of the protons, neutrons, and electrons in the universe today were created in the first few seconds after the BigBang.

Electroweak Baryogenesis?
Electroweak Phase Transition (EWPT).

The matter-antimatter asymmetry in the universe could have been produced at the electroweak phase transition, when the electromagnetic and the weak nuclear forces became decoupled. This is the era when the Higgs first acquired a vacuum expectation value (vev), so other particles acquired masses.

Radiation era
The interval of domination by radiation is called the radiation era.

3 minutes

Cosmic Abundance of Helium and Hydrogen

The expanding universe had cooled to below about 109 K so that protons and neutrons could fuse to make stable deuterium nuclei (a hydrogen isotope with one proton and one neutron). Most of the helium in the universe was created from the primordial neutrons and protons (Although stars do produce some of the helium visible today), by the time the nucleosynthesis epoch ended. Stars to fuse hydrogen nuclei to make a helium nucleus use fusion. The fusion chain process in the early universe was slightly different than what occurs in stars because of the abundant free neutrons in the early universe. However, the general process is the same: protons react to produce deuterium (heavy hydrogen), deuterium nuclei react to make Helium-3 nuclei, and Helium-3 nuclei react to make the stable Helium-4 nucleus.
The amount of the final Helium-4 product is not as sensitive to the density of the early universe
The deuterium nucleus is the weak link of the chain process, so the fusion chain reactions could not take place until the universe had cooled enough. The exact temperature depends sensitively on the density at that time. Extremely small amounts of Lithium-7 were also produced during the early universe nucleosynthesis process. Lithium-7 and deuterium density depends sensitively upon the density of protons (2 up + 1 down quarks
) and neutrons during this time. If the universe were too dense, then most of the deuterium would have fused into helium. The more neutrons that decay before combining with protons, the smaller the abundances of heavier elements. Only in a low-density universe can the deuterium survive. A denser universe would have had more deuterium fused to form helium, so the amount of the remaining deuterium seen today is used as a probe of the early density because of the sensitivity of its production to the density of the protons and neutrons and temperature in the early universe.

Comparing the observed densities of the primordial isotopes to those computed from models and translating the results into Omega, the density parameter, gives Omega = 0.015/h2 where h is the Hubble parameter divided by 100 km/sec/Mpc. The smaller Ho, the larger Omega; if Ho=50, Omega is approximately 0.06, whereas Ho=100 gives Omega of only 0.015. This range is still much less than Omega=1, but nucleosynthesis limits can indicate only the density of baryons, because only baryons participate in nuclear reactions. Hence we must conclude that the universe contains less than the critical density of baryons.

After about 15 minutes

Too cold for fusion. Free neutrons and protons were synthesised into the light elements: deuterium (D), helium-3, and helium-4. The universe consisted of 10% helium and 90% hydrogen, (25% helium and 75% hydrogen, by mass).
There were also extremely small amounts of the Lithium-7 produced.
The elements heavier than helium were produced in the cores of stars.

The number of deuterium nuclei that do not later undergo fusion reaction to make Helium-3 nuclei also depends sensitively on the temperature and density of the protons and neutrons. A less dense universe would have had more deuterium remaining. Therefore, measurement of the primordial deuterium can show if there is enough matter to make the universe positively-curved and eventually stop the expansion.

10,000 yearsThe cosmic background radiation (CBR)

The radiation temperature IS about 3000 degrees Kelvin.


About 100,000 years map of the universe after the Big Bang, the temperature of the Universe had dropped sufficiently for electrons and protons to combine into hydrogen atoms, p + e --> H. From this time onwards, radiation was effectively unable to interact with the background gas; it has propagated freely ever since, while constantly losing energy because its wavelength is stretched by the expansion of the Universe. You can switch on your TV and `detune it` the static you detect is the radiation of the Universe at a very early stage on what is known as the `surface of last scattering'. Photons in the cosmic microwave background have been travelling towards us for over ten billion years, and have covered a distance of about a million billion billion miles.
The heavier elements, of which we are partly made, were created later in the interiors of stars and spread widely in supernova explosions.

1 MILLION YEARS Ordinary matter consisted of hot plasma of nuclei and electrons. The free electrons made the plasma opaque; a photon of radiation could not have travelled far before being scattered. However, once the universe cooled to approximately 3000 K, the electrons did not have enough energy to escape the pull of the nuclei, and atoms were created. This EVENT is known as recombination. Before this time the universe was opaque, and forms the surface of last scattering. No optical telescopes can see past this opaque plasma. . These photons at the surface of last scattering make up the Cosmic Background Radiation. Their energy has been red-shifted to the microwave wavelength. At some point before or near recombination, the matter density and the energy density were equally important. This is the epoch in which large-scale structure formation began. Large-scale structure formation could not have begun earlier, during the GUT epoch, because of the tight coupling between radiation and matter stopping the density perturbations from forming. Once matter and radiation were separated, density perturbations could evolve on their own. The most over dense areas collapsed gravitationally, forming galaxies and clusters of galaxies. Less dense areas formed voids, the large under dense areas we see on the sky today.

TODAY

Cosmic background radiation (CBR) is only 3K.





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