Modern Physics Letters A

Possible effects of the non-vanishing sizes of particles (atoms, nuclei, nucleons, quarks, and leptons) in the early universe (the temperature T) are discussed in an extended Friedmann model of the universe (the scale a). In particular we point out the following possibilities: (a) if r_q>(2N_B/π)^-1/3a, most of the proposed scenarios for T>10³TeV including the inflationary universe are unrealistic, (b) r_q<(2N_B/π)^-1/3a due to the smallness of r_q(≲ 10^-27cm), (c) r_q<(2N_B/π)^-1/3a due to the smallness of N_B in which the baryon number (or quark number) must be generated at T≲0³TeV if r_q≳ 10^-17cm (where r_q and N_B are the effective radius of quarks and the baryon number in the universe, respectively), and (d) for T≳ 10³TeV, the universe was filled not with quark–gluon plasma but with "subquark plasma".

Using gravitational action for four-dimensional theory of R²-gravity, it has been shown earlier that, at high energy level, Ricci scalar R behaves like a physical field in addition to its usual nature as a geometrical field. The physical aspect of R is represented by spinless particles, called riccions. It is shown here that riccions can also be obtained from multi-dimensional R²-gravity. Further it is shown that these riccions disintegrate into fermion and anti-fermion pairs under certain conditions. Some physical properties of these fermions (here called riccinos) are discussed. On the basis of the results obtained here, one is tempted to speculate that our physical universe might have emerged through decay of riccions and riccinos.

The variational theory of the perfect fluid with intrinsic spin and dilatonic charge (dilaton-spin fluid) is developed. The spin tensor obeys the classical Frenkel condition. The Lagrangian density of such fluid is stated, and the equations of motion of the fluid, the Weyssenhoff-type evolution equation of the spin tensor and the conservation law of the dilatonic charge are derived. The expressions of the matter currents of the fluid (the canonical energy-momentum three-form, the metric stress-energy four-form and the dilaton-spin momentum three-form) are obtained.

We develop a perturbation theory for evaluating the boundary S-matrix in 2D quantum field theory. We apply this approach to calculate the one-loop boundary S-matrix for the elementary particle of the sine–Gordon model with a boundary interaction. Our perturbative result agrees with the exact expression of the S-matrix conjectured by Goshal; it also allows us to derive the perturbative relation between the parameter ϑ in the S-matrix and the free parameter M in the boundary action, in the particular case in which its other free parameter φ₀ is zero.

Given an associative algebra A generated by {e_k, k=1, 2,…} and with an internal law of type: , we first show that it is possible to construct a quantum bi-algebra with unit and generated by (non-necessarily commutative) elements satisfying the relations: . This leads one to define a quantum homomorphism. We then treat the example of the algebra of functions on a set of N elements and we show, for the case N=2, that the resulting bihyphen;algebra is an inhomogeneous quantum group. We think that this method can be used to construct quantum inhomogeneous groups.

A few analytical results are presented for the bunching parameters analysis applied to study the fluctuations of hadron multiplicity density in high energy collisions. The behaviors of bunching parameters are analyzed in the cases of concatenate and partitioning fluctuations. The effect of pairing in partition is also studied. As the phase-space decreases, the concatenation can be observed as the divergence of one of the bunching parameters, which also implies a strong short range correlation. In the case of a weak short range correlation, both types of binomial partitions lead to saturation for all the bunching parameters. As the phase-space increases, the effects of pair production can be observed as the oscillatory bunching parameters η_q — a function of order q. The characteristics of the observed features are discussed. Comparisons to experimental data are also presented.

A variational approach is applied to the description of temperature effects in an N-particle exactly solvable schematic model, with SU(2) symmetry. The ground-state energy and the strength distribution for different couplings and temperatures are compared with the exact results.

We suggest a super-Poincaré invariant action for closed 11-dimensional superstring. The sector of physical variables xⁱ, θ_a, , with ,…,8 and xⁱ the transverse part of the D=11 x^μ coordinate is shown to possess free dynamics.

In this letter we provide a simple explanation of the recent finding of anisotropy in electromagnetic (EM) propagation claimed by Nodland and Ralston. We consider, as a possible origin of such effect, the effective coupling between EM fields and some tiny background torsion field. The coupling is obtained after integrating out charged fermions, it is gauge-invariant and does not require the introduction of any new physics.