International Journal of Modern Physics A

We discuss cosmology in the context of Liouville strings, characterized by a central-charge deficit Q², in which target time is identified with (the worldsheet zero mode of the) Liouville field: Q-Cosmology. We use a specific example of colliding braneworlds to illustrate the phase diagram of this cosmological framework. The collision provides the necessary initial cosmological instability, expressed as a departure from conformal invariance in the underlying string model. The brane motion provides a way of breaking target-space supersymmetry, and leads to various phases of the brane and bulk Universes. Specifically, we find a hot metastable phase for the bulk string Universe soon after the brane collision in which supersymmetry is broken, which we describe by means of a subcritical worldsheet σ-model dressed by a spacelike Liouville field, representing finite temperature (Euclidean time). This phase is followed by an inflationary phase for the brane Universe, in which the bulk string excitations are cold. This is described by a super-critical Liouville string with a timelike Liouville mode, whose zero mode is identified with the Minkowski target time. Finally, we speculate on possible ways of exiting the inflationary phase, either by means of subsequent collisions or by deceleration of the brane Universe due to closed-string radiation from the brane to the bulk. While phase transitions from hot to cold configurations occur in the bulk string universe, stringy excitations attached to the braneworld remain thermalized throughout, at a temperature which can be relatively high. The late-time behavior of the model results in dilaton-dominated dark energy and present-day acceleration of the expansion of the Universe, asymptoting eventually to zero.

In this paper another class of Dark Matter candidate particles — the pseudoscalar and scalar light bosonic candidates — is discussed. Particular care is devoted to the study of the processes for their detection (which only involves electrons and photons/X-rays) in a suitable underground experimental setup. For this purpose the needed calculations are developed and various related aspects and phenomenologies are discussed. In particular, it is shown that — in addition to the WIMP cases already discussed elsewhere — there is also possibility for a bosonic candidate to account for the 6.3σ C.L. model independent evidence for the presence of a particle DM component in the galactic halo observed by DAMA/NaI. Allowed regions in these scenarios are presented also paying particular care on the cosmological interest of the bosonic candidate.

Invoking the formation of a fireball we analyze the experimental data on pion multiplicity from La + La collision at and its kinetic energy spectrum. We discuss the freeze-out scenario, the possible role of the delta and strange particles and whether the hadronic repulsion (leading to an excluded volume effect) plays any role at the thermochemical and the hydrodynamical freeze-out stage. The importance of collective flow is realized in explaining the pion spectrum at this collision energy. The analysis also provides evidence of the presence of strange particles and the delta resonance in partial chemical equilibrium, at an initial chemical freeze-out stage when the hydrodynamic flow has not developed to have any significant effect. At the final "hydrodynamical freeze-out" we do not find any evidence of the deltas and the strange particles when the thermal temperature has dropped considerably. The importance of the collective flow vis a vis the resonance decay contribution is also discussed in explaining the pion kinetic energy spectra. Further, all the model parameters are determined uniquely, unlike previous analysis, thus avoiding any arbitrariness.

We argue that the geodesic rule, for global defects, is a consequence of the randomness of the values of the Goldstone field ϕ in each causally connected volume. As these volumes collide and coalescence, ϕ evolves by performing a random walk on the vacuum manifold . We derive a Fokker–Planck equation that describes the continuum limit of this process. Its fundamental solution is the heat kernel on , whose leading asymptotic behavior establishes the geodesic rule.

We investigate the general solution with the symmetry ISO(1, p) × SO(9-p) of Type II supergravity (the three-parameter solution) from the viewpoint of the superstring theory. We find that one of the three parameters (c₁) is closely related to the "dilaton charge" and the appearance of the dilaton charge is a consequence of deformations of the boundary condition from that of the boundary state for BPS D-branes. We give three examples of the deformed D-branes by considering the tachyon condensation from systems of -branes, unstable D9-branes and unstable D-instantons to the BPS saturated Dp-branes, respectively. We argue that the deformed systems are generally regarded as tachyonic and/or massive excitations of the open strings on -brane systems.

Considering energy conservation, adopting KKW method, the tunneling effect of global monopole charged black hole was deeply studied. The result shows that the emission of particle on the event horizon relates to the change of Bekenstein–Hawking entropy and the spectrum is not pure thermal. Moreover, the corrections to the entropy and temperature of the black hole are presented.

We present an "algebraic treatment" of the analytical Bethe ansatz for open spin chains with soliton nonpreserving (SNP) boundary conditions. For this purpose, we introduce abstract monodromy and transfer matrices which provide an algebraic framework for the analytical Bethe ansatz. It allows us to deal with a generic open SNP spin chain possessing on each site an arbitrary representation. As a result, we obtain the Bethe equations in their full generality. The classification of finite dimensional irreducible representations for the twisted Yangians are directly linked to the calculation of the transfer matrix eigenvalues.

Using the modern equations of state derived from microscopic calculations, we have calculated the neutron star structure. For the neutron star, we have obtained a minimum mass about 0.1 M_⊙ which is nearly independent of the equation of state, and a maximum mass between 1.47 M_⊙ and 1.98 M_⊙ which is strongly dependent on the equation of state. It is shown that among the equations of state of neutron star matter which we have used, the stiffest one leads to higher maximum mass and radius and lower central density. It is seen that the given maximum mass for the Reid-93 equation of state shows a good consistency with the accurate observations of radio pulsars. We have indicated that the thickness of neutron star crust is very small compared to the predicted neutron star radius.

The analysis of the equivalence between the Hamiltonian and Lagrangian formalisms, for a sp(2) BRST theory, is achieved. The proof of this equivalence, apart from its intrinsic importance, allows the explanation of some results which seem artificially implanted in the theory: the structure of the extended spaces, and the form of the master equation. As a new image on the BRST operator, this paper suggests that its action can be split into a canonical part and a noncanonical part.

A general scheme to find string boundary states is developed within the framework of the theory of KP hierarchy. The method is applied to calculate correlation function of intersecting D-branes and rederived from the results of our previous works as special examples. A matrix generalization of this scheme provides a method to study dynamics of coincident multi D-branes.