Mass loss and axial rotation are playing key roles in shaping the evolution of massive stars. They affect the tracks in the HR diagram, the lifetimes, the surface abundances, the hardness of the radiation field, the chemical yields, the presupernova status, the nature of the remnant, the mechanical energy released in the interstellar medium, etc... In this paper, after recalling a few characteristics of mass loss and rotation, we review the effects of these two processes at different metallicities. Rotation probably has its most important effects at low metallicities, while mass loss and rotation deeply affect the evolution of massive stars at solar and higher than solar metallicities.
The early stage of the Universe is discussed and the time lengths of its first six days, as well as its age, are given. There seems to be no contradiction with the Bible's ascertain that the Universe was created in six days.
The early stage of the Universe is discussed and the time lengths of its first days are given. If we denote the Hubble time in the zero-gravity limit by T (approximately 12.16 billion years), and T(n) denotes the length of the n-th day, then we have the very simple relation T(n)=T/(2n-1). Hence we obtain for the first days the following lenghts of time: T(1)=T, T(2)=T/3, T(3)=T/5, etc.
We develop a stochastic formulation of cosmology in the early universe, after considering the scatter in the redshift-apparent magnitude diagram in the early epochs as an observational evidence for the non-deterministic evolution of early universe. We consider the stochastic evolution of density parameter in the early universe after the inflationary phase qualitatively, under the assumption of fluctuating $w$ factor in the equation of state, in the Fokker-Planck formalism. Since the scale factor for the universe depends on the energy density, from the coupled Friedmann equations we calculated …
In this talk, I will illustrate how one can use the cosmic microwave background anisotropy measurements, in order to test theoretical models aiming at describing the early universe.
Matter collapsing to a singularity in a gravitational field is still an intriguing question. Similar situation arises when discussing the very early universe or a universe recollapsing to a singularity. It is suggested that inclusion of mutual gravitational interactions among the collapsing particles can avert a singularity and give finite value for various physical quantities like entropy, density, etc.
The ingredients required to create a magnetic field in the early Universe are identified, and compared with Sakharov's conditions for baryogenesis. It is also shown that a long range coherent magnetic field is not generated by the classical rolling Higgs vacuum expectation value during the electroweak phase transition.
We investigate the possible effect of the residual annihilations of heavy particles after freeze-out from equilibrium in the early universe. An error in previous work on this subject is pointed out and the correct method of solving the Boltzmann equation for this case is developed. For Majorana particles there are significant differences relative to previous work.
Within an early Universe scenario, nonextensive thermostatistics (NET) is investigated on the basis of data concerning primordial Helium abundance. We obtain first order corrections to the energy densities and weak interactions rates, and use them to compute the deviation in the primordial Helium abundance. After compare with observational results, a severe bound is stablished.
The cosmic microwave background radiation (CMBR) is providing important clues into the evolution of the early universe. In this Science Perspective, Joy and Carlstrom discuss one feature of the CMBR, the Sunyaev-Zel'dovich effect, which can be used to determine the abundance and evolution of clusters of galaxies, thereby constraining key cosmological parameters such as the matter density of the universe and its expansion rate.
Topological defects are common in many everyday systems. In general, they appear if a symmetry is broken at a rapid phase transition. In this article, I explain why it is believed that they should have also been formed in the early universe and how that would have happened. If topological defects are found, this will provide a way to study observationally the first fractions of a second after the Big Bang, but their apparent absence can also tell us many things about the early universe.
Atomic and molecular transitions for high Z objects in the early universe give bounds to the possible existence of extra spatial dimensions $D = 3+ε$. We review the theory and present observational data, based on Lyman and Balmer hydrogen transitions of distant quasars and CO rotational transitions of far away giant molecular clouds.
We present a general set of calculations decribing the chemical evolution of young massive galaxies and predict the evolution of the CO, O2, and dust abundances as a function of age and metallicity.
In these lectures we dwell upon the cosmological corner-stones of the Very Early Universe (VEU) theory: Parametric Amplification Effect (PAE) responsible for the generation of Primordial Cosmological Perturbations (PCPs), Chaotic and Stochastic Inflation, Principal Tests of VEU, and others.
At early times the Universe was filled up with an extremely dense and hot gas. Due to the expansion it cooled below the binding energies of atoms which led to the formation of the first nuclei. In the physical environment of the post-recombination period of hydrogen, molecules such as $H_2$, $HD$ and $LiH$ can be formed. The proto-object formation, resulting from the growth of linear density fluctuations in the early Universe, can have an important impact on the chemical state of the Universe. Hence it can be enriched with metals, and thus lead to the formation of the first pre-biotic molecule…
We discuss the concept of measurement in cosmology from the relativistic and quantum mechanical points of view. The uncertainty principle within the particle horizon, excludes the momentum of particles to be less than $π\hbar H/c$. This effect modifies the standard thermodynamics of early universe for the ultra-relativistic particles such that the equation of state as well as dependence of energy density and pressure to the temperature. We show that this modification to the thermodynamics of early universe is important for energies $E>10^{17} GeV$. During the inflation, the particle horizon in…
We present aspects of a model which attempts to unify the creation of cold dark matter, a CP-violating baryon asymmetry, and also a small, residual vacuum energy density, in the early universe. The model contains a primary scalar (inflaton) field and a primary pseudoscalar field, which are initially related by a cosmological, chiral symmetry. The nonzero vacuum expectation value of the pseudoscalar field spontaneously breaks CP invariance.
Old, metal-poor globular clusters trace the formation and evolution of early-type galaxies. Their are the best probes, at low redshift, of the building-up of galaxy halos at high redshift. Their properties constrain the characteristics of their progenitors. Recent results suggest that DLAs at z>3 are the likely hosts for their formation. Finally, they shed light on the old, metal-poor halos probably present around all early-type galaxies.
We investigate the observability of hydrogen molecules in absorption. The absorption efficiency of the hydrogen molecules become comparable with or larger than that of the dust grains in the metal-poor condition expected in the early Universe. If we can use bright infrared continuum sources behind the molecular gas clouds, the absorption measurement of the hydrogen molecules will be an important technique to explore the primordial gas clouds that are contracting into first-generation objects.
Temperature and polarization power spectra of the cosmic microwave background can provide essentially incontrovertible evidence for coherent acoustic oscillations in the early universe. A simple model calculation demonstrates explicitly how polarization couples to velocities at the surface of last scatter and is nearly independent of gravitational or density perturbations. For coherent acoustic oscillations, peaks in the temperature and polarization power spectra are precisely interleaved. If observed, such a signal would provide strong support for initial density perturbations on scales large…
In the framework of inflationary models with non-vacuum initial states for cosmological perturbations, we study non-Gaussian signatures on the cosmic microwave background radiation produced by a broken-scale-invariant model which incorporates a feature at a privileged scale in the primordial power spectrum.
The observational and theoretical status of neutrino oscillations in connection with solar and atmospheric neutrino anomalies is presented in brief. The effect of neutrino oscillations on the early Universe evolution is discussed in detail. A short review is given of the standard Big Bang Nucleosynthesis and the influence of resonant and nonresonant neutrino oscillations on active neutrinos and on primordial nucleosynthesis of He-4. BBN cosmological constraints on neutrino oscillation parameters are discussed.
Observational data on the early galactic abundances of the light elements lithium, beryllium and boron are combined with data related to the reionization of the intergalactic medium (IGM) in a search of processes happening in the early universe. Early massive metal-free stars (Pop III), largely held responsible for the reionization of the IGM, are proposed to have been also at the origin of the lithium-6 plateau, through their winds. In this sense the evolution of the Li-6/Be-9 ratio appears to be a key parameter for the history of nucleosynthesis, as a monitor of the early formation of metals…
Recent key observational results on the variation of fine structure constant, the proton to electron mass ratio and the gravitational constant are reviewed. The necessity to substantiate the dark sector of cosmology and to test gravity on astrophysical scales is also emphasized.
In the previous parts of the discussion on the same topic, various aspects of the very early universe were discussed. We discussed how inclusion of large dark energy term compensates for the net gravity. Here the discussion is taken further including the effects of charge, magnetic fields and rotation. The role of large extra dimensions under the extreme initial conditions is discussed and possible connection with the cyclic brane theory is explored. We constrain various cosmic quantities like the net charge, number density of magnetic monopoles, primordial magnetic fields, size of the extra d…
It is shown, for the first time , that surprisingly the electric charge loses all physical meaning above the electro-weak phase transition temperature. Implications of this discovery in the context of the early universe within the framework of various unified models are discussed.
We discuss the cosmological consequences of QCD phase transition(s) on the early universe. We argue that our recent knowledge about the transport properties of quark-gluon plasma (QGP) should throw additional lights on the actual time evolution of our universe. Understanding the nature of QCD phase transition(s), which can be studied in lattice gauge theory and verified in heavy ion experiments, provides an explanation for cosmological phenomenon stem from early universe.
We expose briefly the role of entropy in the early universe and in particular the importance of searching for new mechanisms of entropy production. We describe a mechanism that shows how entropy is produced during early annihilations and under which conditions the production is not negligible. A MeV tau neutrino provides an interesting application.
In this report of the workshop on `Physics of the Very Early Universe' held at GR14, the recent status and open problems in a selected number of major areas of interest are reviewed, focusing on attempts to develop a superstring cosmology and on progress in understanding current theories of structure formation.
An introductory account is given of the modern understanding of the physics of the early Universe. Particular emphasis is placed on the paradigm of cosmological inflation, which postulates a period of accelerated expansion during the Universe's earliest stages. Inflation provides a possible origin for structure in the Universe, such as microwave background anisotropies, galaxies and galaxy clusters; these observed structures can therefore be used to test models of inflation. A brief account is given of other early Universe topics, namely baryogenesis, topological defects, dark matter candidate…
Loop quantum cosmology applies techniques derived for a background independent quantization of general relativity to cosmological situations and draws conclusions for the very early universe. Direct implications for the singularity problem as well as phenomenology in the context of inflation or bouncing universes result, which will be reviewed here. The discussion focuses on recent new results for structure formation and generalizations of the methods.
In the early Universe matter was crushed to high densities, in a manner similar to that encountered in gravitational collapse to black holes. String theory suggests that the large entropy of black holes can be understood in terms of fractional branes and antibranes. We assume a similar physics for the matter in the early Universe, taking a toroidal compactification and letting branes wrap around the cycles of the torus. We find an equation of state p_i=w_i rho, for which the dynamics can be solved analytically. For black holes, fractionation can lead to non-local quantum gravity effects across…
In this talk I will describe the role of supersymmetric flat directions in the early Universe cosmology. Particularly I will discuss how supergravity effects lift the flat direction potential and leads to interesting cosmological consequences.
We investigate the mixing of heavy gauge singlet neutrinos in a mirror matter model employing the seesaw mechanism. The parameter constraints that must be satisfied to prevent the overproduction of mirror matter in the early universe are deduced. We find that no fine tuning in the heavy neutral fermion sector is required for this mirror matter model to satisfy cosmological constraints. Baryogenesis scenarios are briefly discussed in the context of the mirror model.
A simple perturbation description unique for all signs of curvature, and based on the gauge-invariant formalisms is proposed to demonstrate that: (1) The density perturbations propagate in the flat radiation-dominated universe in exactly the same way as electromagnetic or gravitational waves propagate in the epoch of the matter domination. (2) In the open universe, sounds are dispersed by curvature. The space curvature defines the minimal frequency $ω_{\rm c}$ below which the propagation of perturbations is forbidden. Gaussian acoustic fields are considered and the curvature imprint in the per…
Supersymmetric flat directions can have a number of important consequences in the very early universe. Depending on the form of the SUSY breaking potential arising from the finite energy density at early times, coherent production of scalar condensates can result along such directions. This leads a cosmological disaster for Polonyi type flat directions with only Planck suppressed couplings, but can give rise to the baryon asymmetry for standard model flat directions. Flat directions are also natural candidates to act as inflatons. Achieving density fluctuations of the correct magnitude general…
We examine in the context of supersymmetric models whether the usual cosmological upper bound on the axion decay constant can be relaxed by assuming a period of stronger QCD in the early universe. By evaluating the axion potential in the early universe and also taking into account the dilaton potential energy, it is argued that a stronger QCD is not useful for raising up the bound.
Very recently, it has been shown by the author that the Standard Model Higgs cannot be a physical particle. Here, on most general grounds it is established that as per the Standard Model there is no electric charge above the electro-weak phase transition temperature. Hence there was no electric charge present in the early universe. The Superstring Theories are flawed in as much as they are incompatible with this requirement. Hence the Superstring Theories are inconsistent with this basic structure and requirement of the Standard Model.
We study the modified theory of gravity in Friedmann Robertson Walker universe composed of several perfect fluids. We consider the power law inflation and determine the equation of state parameters in terms of the parameters of modified gravity's Lagrangian in the early universe. We also discuss briefly the gravitational baryogenesis in this model.
Two introductory lectures on inflation and dark matter presented at the NATO Advanced Study Institute on Techniques and Concepts of High-Energy Physics.
In the early universe, neutrinos decouple from equilibrium with the electromagnetic plasma at a temperature which is only slightly higher than the temperature where electrons and positrons annihilate. Therefore neutrinos to some extent share in the entropy transfer from e^+e^- to other species, and their final temperature is slightly higher than the canonical value T_nu = (4/11)^{1/3} T_gamma. We study neutrino decoupling in the early universe with effects of neutrino oscillations included, and find that the change in neutrino energy density from e^+ e^- annihilations can be about 2-3% higher …
Using a formalism recently introduced we study the decaying of the cosmological parameter during the early evolution of an universe, whose evolution is governed by a vacuum equation of state. We use a stochastic approach in a nonperturbative treatment of the inflaton field from a Noncompact Kaluza-Klein (NKK) theory, to study the evolution of energy density fluctuations in the early universe.
After a brief summary of general relativity and cosmology, we present the basic concepts underlying inflation, the currently best motivated models for the early Universe. We describe the simplest inflation models, based on a single scalar field, and discuss how primordial cosmological perturbations are generated. We then review some recent developments concerning multi-field inflation models, in particular multi-field Dirac-Born-Infeld inflation.
Quantum electrodynamics predicts that photons undergo one-loop scattering. The combined effect of this on the behaviour of a photon gas for temperatures above 10^{10} K results in a softening of the equation of state. We calculate the effect this has on the effective equation of state in the early universe, taking into account all the species of the Standard Model. The change to the dynamics of the early universe is discussed.
In the context of current particle physics theories, it is quite likely that topological defects may be present in our universe. An observation of these fossils from the early universe would lead to invaluable insight into cosmology and particle physics, while their absence provides important constraints on particle-cosmology model building. I describe recent efforts to address cosmological issues in condensed matter systems such as He-3 and a possible solution to the magnetic monopole problem due to defect interactions. (Invited talk at the 1997 RESCEU Symposium, University of Tokyo.)
Using a previously introduced model in which the expansion of the universe is driven by a single scalar field subject to gravitational attraction induced by a white hole during the expansion (from a 6D vacuum state), we study the origin of squared inflaton fluctuations spectrum on astrophysical scales.
Appealing to classical methods of order reduction, we reduce the Lifshitz system to a second order differential equation. We demonstrate its equivalence to well known gauge-invariant results. For a radiation dominated universe we express the metric and density corrections in their exact forms and discuss their acoustic character.
I explore some consequences of Milgrom's modified dynamics for cosmology. There appear to be two promising tests for distinguishing MOND from CDM: (1) the rate of growth of structure and (2) the baryon fraction. These should be testable with observations of clusters at high redshift and the microwave background, respectively.
We put limits on the time variation of the electron mass in the early universe using observational primordial abundances of D, He4 and Li7, recent data from the Cosmic Microwave Background and the 2dFGRS power spectrum. Furthermore, we use these constraints together with other astronomical and geophysical bounds from the late universe to test Barrow-Magueijo's model for the variation in m_e. From our analysis we obtain -0.615 < Gω/c^4 < -0.045 (3σinterval) in disagreement with the result obtained in the original paper.
In this letter we complete a previously introduced formalism to study the gauge-invariant metric fluctuations from a noncompact Kaluza-Klein theory of gravity, to study the evolution of the early universe. The evolution of both, metric and inflaton field fluctuations are reciprocally related. We obtain that <δρ/ρ_b$ depends on the coupling of $Φ$ with $δϕ$ and the spectral index of its spectrum is: $0.9483 < n_1 < 1$.
According to the inflationary scenario for the very early Universe, all inhomogeneities in the Universe are of genuine quantum origin. On the other hand, looking at these inhomogeneities and measuring them, clearly no specific quantum mechanical properties are observed. We show how the transition from their inherent quantum gravitational nature to classical behaviour comes about -- a transition whereby none of the successful quantitative predictions of the inflationary scenario for the present-day universe is changed. This is made possible by two properties. First, the quantum state for the sp…
