Fortschritte Der Physik-Progress of Physics最新文献

We formulate scalar electrodynamics in the braided $�L_{\infty }$-algebra formalism and study its perturbative expansion in the algebraic framework of Batalin–Vilkovisky quantization. We also confirm that UV/IR mixing is absent at one-loop order in this noncommutative field theory, and that the non-anomalous Ward-Takahashi identities for the braided gauge symmetry are satisfied.

Motivated by the notion that the mathematics of gravity can be reproduced from a statistical requirement of maximal entropy, the consequences of introducing an entropic source term in the Einstein–Hilbert action are studied. For a spatially homogeneous cosmological system driven by this entropic source and enveloped by a time-evolving apparent horizon, a modified version of the second law of thermodynamics is formulated. An explicit differential equation governing the internal entropy profile is found. Using a Hessian matrix analysis of the internal entropy, the author checked the thermodynamic stability for three categorically different toy models describing (i) a $��\Lambda �\mathrm{CDM}�$ cosmology, (ii) a unified cosmic expanson, and (iii) a non-singular ekpyrotic bounce. The mathematical condition for a second order phase transition during these evolutions from the divergence of specific heat at constant volume is found. The new-found condition is purely kinematic and quadratic in nature, relating the deceleration parameter and the jerk parameter that chalks out an interesting curve on the parameter space. This condition is valid even without the entropic source term and may be treated as a general property of any phase transition.

The late time behavior of the slow-roll parameter in the stringy quintessence model is studied when axion as well as saxion are allowed to move. Even though the potential is independent of the axion at tree level, the axion can move through its coupling to the saxion and the background geometry. Then the contributions of the axion kinetic energy to the slow-roll parameter and the vacuum energy density are not negligible when the slow-roll approximation does not hold. As the dimension of the field space is doubled, the fixed point at which the time variation of the slow-roll parameter vanishes is not always stable. It is found that the fixed point in the saxion–axion system is at most partially stable, in particular when the volume modulus and the axio-dilaton, the essential ingredients of the string compactification, are taken into account. It seems that as more saxion–axion pairs are considered, achieving the stability of the fixed point becomes difficult.

It was recently shown that integrating out M2 states on Calabi-Yau manifolds captures non-perturbative topological string physics in the free energy. In this note, It has been shown that the resulting expression manifests a certain duality symmetry: the free energy at strong string coupling is equal to the Calabi-Yau period at weak string coupling. The duality yields the appropriate prescription for completing the integrating out in the ultraviolet.

This article shows that the integral flow-lines of the RG-flow of open string theory can be interpreted as the solitons of a Hořova–Lifshitz sigma-model of open membranes. The authors argue that the effective background description of this model implies the g-theorem of open string theory. Its close connection to boundary string field theory is described. Additionally, the study endows the Hilbert space of the open membrane with a graded non-commutative, associative, cyclic algebra and construct an open membrane field theory, whose action measures the energy difference between different backgrounds in open string field theory. The authors use an identity-based membrane field to proof Sen's conjecture. Finally, the ideas are applied to the topological string and it is shown that the membrane action is quantized in equivariant K-theory of the moduli space of framed instantons.

Four $��S�U�\left(�5�\right)��N�=�1�$ supersymmetric models which exhibit $�S_3$ and/or $�Z_N$ symmetries are studied, that are finite to two or all loops, and their corresponding mass matrices. The first is an all-loop finite model based on an $��S_3�\times �Z_3�\times �Z_2�$ flavor symmetry, which leads to phenomenologically nonviable mass matrices. The remaining models, based on cyclic symmetries, show various mass textures, some of which are phenomenologically promising. For the two-loop finite models, the parametric solutions to the finiteness conditions determine completely some of the Yukawa couplings, and lead to a restricted range of values for other ones at the GUT scale, with a considerable reduction in the number of free parameters. One particular solution of the two-loop models shows an enhanced symmetry, leading to an all-loop finite model, which has a significant parameter reduction and could in principle reproduce the observed quark masses and mixing pattern. In this case the finiteness conditions determine the absolute value of all the Yukawa couplings at the unification scale. Finally, the minimum number of phases in the mass matrices and their position are determined, a task not previously done in Finite Unified Theories, which contributes towards the reduction of parameters and a better understanding of the Yukawa couplings.