Supernova bangs as a tool to study big bang

Supernovae and gamma-ray bursts are the most powerful explosions in observed Universe. This educational review tells about supernovae and their applications in cosmology. It is explained how to understand the production of light in the most luminous events with minimum required energy of explosion. These most luminous phenomena can serve as primary cosmological distance indicators. Comparing the observed distance dependence on red shift with theoretical models one can extract information on evolution of the Universe from Big Bang until our epoch.     

Was the big bang a whimper?

In many cases the spatially homogeneous cosmological models of General Relativity begin or end at a “big bang” where the density and temperature of the matter in the universe diverge. However in certain cases the spatially homogeneous development of these universes terminates at a singularity where all physical quantities are well—behaved (a “whimper”) and an associated Cauchy horizon. We examine the existence and nature of these singularities, and the possible fate of matter which crosses the Cauchy horizon in such a universe. The nature of both kinds of singularity is illustrated by simple models based on two-dimensional Minkowski space-time; and the possibility of other types of singularity occuring is considered.     

The big bang for beginners

A review of The Origin of the Universe. By J. D. Barrow. (Weidenfeld & Nicolson, 1994.) [Pp. xv + 150.] £9·99 (hbk). ISBN 0 297 81497 4. Scope: popular review. Level: general reader.     

A cosmology without big bang

In contrast to standard ECSK theory with the Brans-Dicke scalar field () nonminimally coupled to the curvature scalar, an additional new pseudo scalar term ⁿ E R (contraction between Levi-Civita pseudo tensor and curvature tensor) has been included in the Lagrangian. The new term is non-zero due to the non-symmetric nature of the connection and vanishes identically in the general theory of relativity. We show that there exists a nonsingular cosmological solution for a spatially flat (k=0) Robertson-Walker line element in the radiation era; therefore our model has no big bang.     

Quantum nature of the big bang

Some long-standing issues concerning the quantum nature of the big bang are resolved in the context of homogeneous isotropic models with a scalar field. Specifically, the known results on the resolution of the big-bang singularity in loop quantum cosmology are significantly extended as follows: (i) the scalar field is shown to serve as an internal clock, thereby providing a detailed realization of the "emergent time" idea; (ii) the physical Hilbert space, Dirac observables, and semiclassical states are constructed rigorously; (iii) the Hamiltonian constraint is solved numerically to show that the big bang is replaced by a big bounce. Thanks to the nonperturbative, background independent methods, unlike in other approaches the quantum evolution is deterministic across the deep Planck regime.     

Exotic relics from the big bang

New, exotic (very heavy and/or very weakly interacting) particles would have been produced in the hot, dense environment of the early Universe. If sufficiently long-lived, some exotic relics would have survived to influence the subsequent evolution of the Universe; some may be present today. The laboratory and astrophysical information which can constrain the properties of such new particles is outlined and guidelines are presented for testing models of elementary particle physics.     

Supersymmetric relics from the big bang

We consider the cosmological constraints on supersymmetric theories with a new, stable particle. Circumstantial evidence points to a neutral gauge/Higgs fermion as the best candidate for this particle, and we derive bounds on the parameters in the lagrangian which govern its mass and couplings. One favored possibility is that the lightest neutral supersymmetric particle is predominantly a photino $\text{～}\text{γ}$ with mass above $\text{1}\text{2}$ GeV, while another is that the lightest neutral supersymmetric particle is a Higgs fermion with mass above 5 GeV or less than O(100) eV. We also point out that a gravitino mass of 10 to 100 GeV implies that the temperature after completion of an inflationary phase cannot be above 10¹⁴ GeV, and probably not above 3 × 10¹² GeV. This imposes constraints on mechanisms for generating the baryon number of the universe.     

Pregeometric origin of the big bang

The temperature-dependent effective action for gravity is calculated in pregeometry. It indicates that the effective potential for the space-time metric has the minimum at the origin for extremely high temperature. The origin of the big bang can be taken as a local and spontaneous phase transition of the space-time from the pregeometric phase to the geometric one.     

The big bang is not needed

Recent computer simulations indicate that a system ofn gravitating masses breaks up, even when the total energy is negative. As a result, almost any initial phase-space distribution results in a universe that eventually expands under the Hubble law. Hence Hubble expansion implies little regarding an initial cosmic state. Especially it does not imply the singularly dense superpositioned state used in the big bang model.     

Five-dimensional null-cone structure of big bang singularity

Firedmann model of positive space curvature, vanishing pressure and cosmological constant when isometrically imbedded as a hypersurface in five dimensional Minkowski spaceM ⁵ is globally rigid: if F() and F() are isometric imbeddings inM ⁵ there is a motion of M⁵ such that F= °f. The big bang singularity is the vertex of a null half-cone inM ⁵. Global rigidity leads to an invariant characterization of the singularity. The structure of matter at the singularity is governed by the de Sitter group.     

Strange matter and big bang helium synthesis

Stable strange quark matter produced in the QCD phase transition in the early universe will trap neutrons and repel protons, thus reducing primordial helium production, Y_p. For reasonable values of Y_p, the radius of strange droplets must exceed 10^?6 cm if strange matter shall solve the dark-matter problem without spoiling Big Bang helium synthesis.     

Particle physics catalysis of thermal big bang nucleosynthesis

We point out that the existence of metastable, tau>10(3) s, negatively charged electroweak-scale particles (X-) alters the predictions for lithium and other primordial elemental abundances for A>4 via the formation of bound states with nuclei during big bang nucleosynthesis. In particular, we show that the bound states of X- with helium, formed at temperatures of about T=10(8) K, lead to the catalytic enhancement of 6Li production, which is 8 orders of magnitude more efficient than the standard channel. In particle physics models where subsequent decay of X- does not lead to large nonthermal big bang nucleosynthesis effects, this directly translates to the level of sensitivity to the number density of long-lived X- particles (tau>10(5) s) relative to entropy of nX-/s less, approximately <3x10(-17), which is one of the most stringent probes of electroweak scale remnants known to date.     

Neutrino astronomy and massive long-lived particles from the big bang

We consider the neutrino flux from the decay of long-lived big-bang particles. The red-shift z_tr at which the neutrino transparency of the universe sets in is calculated as a function of neutrino energy: z_tr 1 × 10⁵ for TeV neutrinos and z_tr 3 × 10⁶ for 10 MeV neutrinos. One might expect the production of detectable neutrino flux at z z_tr, but, as demonstrated in this paper, the various upper limits, most notably due to nucleosynthesis and diffuse X- and gamma-rays, preclude this possibility. Unless the particle decay is strongly dominated by the pure neutrino channel, observable neutrino flux can be produced only at the current epoch, corresponding to red-shift z ≈ 0. For the thermal relics which annihilate through the gauge bosons of SU(3)×SU(2)×U(1) group, the neutrino flux can be marginally detectable at 0.1 < E_v < 10 TeV. As an example of non-thermal relics we consider gravitinos. If gravitinos are the lightest supersymmetric particles (LSP) they can produce the detectable neutrino flux in the form of a neutrino line with energy , where M_G is the gravitino mass. The flux strongly depends on the mechanisms of R-parity violation. It is shown that heavy gravitinos (M_G 100 GeV) can make up the dark matter in the universe.