G. Paál

Inflation and compactification from Galaxy redshifts

The distribution of galaxies in the pencil-beam surveys of Broadhurstet al. which proved periodical across 8–10 consecutive steps in a flat dust model withq0=0.5 is found to reveal extended periodicity up to 16–17 phase-coherent steps, covering the total sample, in a flat, moderately inflationary model withq0=−0.5 (vacuum/dust ratio 2/1). In the latter model the vacuum component helps to reach the critical density and lengthens the expansion time-scale. It is shown that the explanation of the found periodicity as a consequence of space compactification as suggested by G. Paál twenty years ago in connection with apparent quasar periodicities is still possible.

Symmetry breaking gut phase transitions with irreversibilities

Abstract For some values of the GUT energy scale parameter, irreversibilities essentially modify the cosmological expansion and may drive inflation even without supercooling. Since in this case the GUT phase transition is affected too, a proper dynamical treatment of the evolution of the early universe is given.

Entropy production in tepid inflation

Abstract We demonstrate that tepid inflation at moderate temperature may be accompanied by entropy enhancement sufficient to dilute the GUT monopoles below the observational limit.

ONCE MORE ON QUASAR PERIODICITIES

In an earlier paper Arp, Bi, Chu and Zhu investigated various quasar samples and recognized a periodicity of remarkable degree in them. Their conclusion was that the existence of such a periodicity is a counterevidence against the cosmological origin of quasar redshifts. Since this question is of great importance in a cosmological context, here we reanalyze some of the samples together with a galaxy sample of the pencil-beam survey of Broadhurstet al. Our result is that on the plane of cosmological parameters (Ω0, λ0) there is a non-negligible region where two quasar samples and the galaxy sample are simultaneously fairly periodic. Pure periodicity is still compatible with cosmological principles, at least on length scales much longer than the period length. So the regularities can fit into a cosmological context.

Nontrivial Pfaffian forms in cosmology

The compatibility of possible continuous cosmologic particle creation with thermodynamics is studied. It is found that with the usualK=2 Pfafflan (dQ=TdS) is compatible only in very special cases.K≥3 Pfafflans can easily be reconciled with continuous creation. Since then the full thermodynamic state space is accessible by quasistatic adiabatic processes, such systems show local rather than global irreversibility. This property may prevent Heat Death even with idefinitely old model Universes.

Galaxy formation from tepid inflation

It is argued that the primordial density fluctuations needed for galaxy formation may have been of thermal origin in a quasi-exponential state of inflation.

Thermodynamics of the vacuum

The fact that the energy-momentum tensor has nonzero vacuum expectation value in some space-times (the so-called back reaction) indicates a nontrivial thermodynamics of such vacua. A consequent thermodynamic analysis of the problem in Robertson-Walker space-times shows that, in the generic case, the number of the independent extensives is 2, in spite of the fact that the energy density is completely determined by the time-evolution of the geometry since the preparation of the vacuum state. The appearance of a second independent extensive seems to be in direct connection with the extra entropy term in theGeneralized Second Law of Bekenstein and Hawking.

Technical constraints for the GUT scale parameter

The influence of the Grand Unification scale on the thermal history of the early Universe is discussed. AboveM≈6.8·1015 GeV the irreversibilities seem to be too strong to ignore them, and the usual calculations lose their validity. Therefore at such scale parameters the low upper bound yielded by observations for the monopole entropy ratio is not neccessarily a counterevidence against the minimal SU(5) GUT.