International Journal of Modern Physics A

It is a challenge to explain why neutrinos are so light compared to other leptons. Small neutrino masses can be explained if right-handed fermions propagate in large extra dimensions. Fermions propagating in the bulk would have implications on Higgs boson decays. If the Higgs boson is discovered at the Large Hadron Collider (LHC), a detailed analysis may reveal the presence of large extra dimensions. This paper reviews the status of large extra-dimensional models in the context of the current limits on Higgs boson masses and the fundamental Planck scale in extra dimensions.

Within Yang–Mills gravity with translation group T(4) in flat space–time, the invariant action involving quadratic translation gauge-curvature leads to quadrupole radiations, which are shown to be consistent with experiments. The radiation power turns out to be the same as that in Einstein's gravity to the second-order approximation. We also discuss an interesting physical reason for the accelerated cosmic expansion based on the long-range Lee–Yang force of U_b(1) gauge field associated with the established conservation law of baryon number. We show that the Lee–Yang force can be related to a linear potential ∝ r, provided the gauge field satisfies a fourth-order differential equation in flat space–time. Furthermore, we consider an experimental test of the Lee–Yang force related to the accelerated cosmic expansion. The necessity of generalizing Lorentz transformations for accelerated frames of reference and accelerated Wu–Doppler effects are briefly discussed.

We study effective gauge theory at finite temperature on a three-sphere in the presence of an IR cutoff using AdS/CFT. Comparing with the thermodynamic behavior of its gravity dual, we analyze a phenomenological matrix model which describes the gauge theory in the strongly coupled regime. Subsequently, we study the behavior of the model as a function of the IR cutoff. We further argue that a similar matrix model represents the effective gauge theory on R³ with an IR-cutoff and analyze the model numerically.

We discuss some of the issues relating to information loss and black hole thermodynamics in the light of recent work on local black hole horizons. Understood in terms of pure states evolving into mixed states, the possibility of information loss in black holes is closely related to the global causal structure of space–time, as is the existence of event horizons. However, black holes need not be defined by event horizons, and in fact we argue that in order to have a fully unitary evolution for black holes, they should be defined in terms of something else, such as a trapping horizon. The Misner–Sharp mass in spherical symmetry shows very simply how trapping horizons can give rise to black hole thermodynamics, Hawking radiation and singularities. We show how the Misner–Sharp mass can also be used to give insights into the process of collapse and evaporation of locally defined black holes.

This paper is concerned with the development of a gravitational field theory having locally a covariant version of the Galilei group. We show that this Galilean gravity can be used to study the advance of perihelion of a planet, following in parallel with the result of the (relativistic) theory of general relativity in the post-Newtonian approximation.

We study pair-production as well as the triple self-couplings of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) at the future International Linear e⁺e^- Collider (ILC) and Compact Linear Collider (CLIC). The analysis is based on the reactions with h_i = h, H, A. We evaluate the total cross-section for both and calculate the total number of events considering the complete set of Feynman diagrams at tree-level. We vary the triple couplings κλ_hhh, κλ_Hhh, κλ_hAA, κλ_HAA, κλ_hHH and κλ_HHH within the range κ = -1 and +2. The numerical computation is done for the energies expected at the ILC with a center-of-mass energy 500, 1000, 1600 GeV and a luminosity 1000 fb^-1. The channels and are also discussed to a center-of-mass energy of 3 TeV and luminosities of 1000 fb^-1 and 5000 fb^-1.

A novel method for quantization of non-Lagrangian (open) systems is proposed. It is argued that the essential object, which provides both classical and quantum evolution, is a certain canonical two-form defined in extended velocity space. In this setting classical dynamics is recovered from the stringy-type variational principle, which employs umbilical surfaces instead of histories of the system. Quantization is then accomplished in accordance with the introduced variational principle. The path integral for the transition probability amplitude (propagator) is rearranged to a surface functional integral. In the standard case of closed (Lagrangian) systems the presented method reduces to the standard Feynman's approach. The inverse problem of the calculus of variation, the problem of quantization ambiguity and the quantum mechanics in the presence of friction are analyzed in detail.

The experiments at LHC have shown that the SUSY (exotic) bound states are likely to form bound states in an entirely similar fashion as ordinary quarks form bound states, i.e. quarkonium. Also, the interaction between two squarks is due to gluon exchange which is found to be very similar to that interaction between two ordinary quarks. This motivates us to solve the Schrödinger equation with a strictly phenomenological static quark–antiquark potential: using the shifted large N-expansion method to calculate the low-lying spectrum of a heavy quark with antisbottom and sbottom with antisbottom bound states with is set free. To have a full knowledge on spectrum, we also give the result for a heavier as well as for lighter sbottom masses. As a test for the reliability of these calculations, we fix the parameters of this potential by fitting the spin-triplet (n³S₁) and center-of-gravity l≠0 experimental spectrum of the ordinary heavy quarkonia , and to few MeV. Our results are compared with other models to gauge the reliability of these predictions and point out differences.

The phase structure of a model with a scalar type eight-fermion interaction is investigated in weakly curved space–time. The ground state of the model is obtained by observing the minimum of the effective potential. Applying the Riemann normal coordinate expansion, we calculate an effective potential of the model in a weakly curved space–time. The result is extended to models with multifermion interactions. We numerically show the behavior of the effective potential and obtain the phase structure of the model.

We discuss the exact solution to Einstein's equation corresponding to a static and plane symmetric distribution of matter with constant positive density located below z = 0 matched to vacuum solutions. The internal solution depends essentially on two constants: the density ρ and a parameter κ. We show that these space–times finish down below at an inner singularity at finite depth . We show that for κ ≥ 0.3513 ⋯, the dominant energy condition is satisfied all over the space–time.

We match these singular solutions to the vacuum one and compute the external gravitational field in terms of slab's parameters. Depending on the value of κ, these slabs are either attractive, repulsive or neutral. The external solution turns out to be a Rindler's space–time. Repulsive slabs explicitly show how negative, but finite pressure can dominate the attraction of the matter. In this case, the presence of horizons in the vacuum shows that there are null geodesics which never reach the surface of the slab.

We also consider a static and plane symmetric nonsingular distribution of matter with constant positive density ρ and thickness surrounded by two external vacuums. We explicitly write down the pressure and the external gravitational fields in terms of ρ and d. The solution turns out to be attractive and remarkably asymmetric: the "upper" solution is Rindler's vacuum, whereas the "lower" one is the singular part of Taub's plane symmetric solution. Inside the slab, the pressure is positive and bounded, presenting a maximum at an asymmetrical position between the boundaries. We show that if , the dominant energy condition is satisfied all over the space–time. We also show how the mirror symmetry is restored at the Newtonian limit.

We also find thinner repulsive slabs by matching a singular slice of the inner solution to the vacuum.

We also discuss solutions in which an attractive slab and a repulsive one, and two neutral ones are joined. We also discuss how to assemble a "gravitational capacitor" by inserting a slice of vacuum between two such slabs.

A sort of calculus is developed to find the chiral algebras of N = 2 superconformal interacting bosonic models. Many examples are discussed. It is shown that the algebras share a common structure, which we call almost Landau Ginzburg. For one or two generators, the number of relations is equal to the number of generators and they are algebraically independent.

The accelerated expansion of the universe has now been confirmed by several independent observations including those of high redshift type Ia supernovae, and the cosmic microwave background combined with the large scale structure of the universe. Another way of presenting this kinematic property of the universe is to postulate the existence of a new and exotic entity, with negative pressure, the dark energy (DE). In spite of observationally well established, no single theoretical model provides an entirely compelling framework within which cosmic acceleration or DE can be understood. At present all existing observational data are in agreement with the simplest possibility that the cosmological constant be a candidate for DE. This case is internally self-consistent and noncontradictory. The extreme smallness of the cosmological constant expressed in either Planck, or even atomic units means only that its origin is not related to strong, electromagnetic, and weak interactions. Although in this case DE reduces to only a single fundamental constant we still have no derivation from any underlying quantum field theory for its small value. From the principles of quantum cosmologies, for example, it is possible to obtain the reason for an inverse-square law for the cosmological constant with no conflict with observations. Despite the fact that this general expression is well known, in this work we introduce families of analytical solutions for the scale factor different from the current literature. The knowledge of the scale factor behavior might shed some light on these questions mentioned above since the entire evolution of a homogeneous isotropic universe is contained in the scale factor. We use different parameters for these solutions and with these parameters we establish a connection with the equation of state for different DE scenarios.

We perform a Noether analysis for a description of translation transformations in 4D κ-Minkowski noncommutative space–time which is based on the structure of a 5D differential calculus. The techniques that had been previously developed for a description of translation transformations based on a 4D differential calculus turn out to be applicable without any modification, and they allow us to show that the basis usually adopted for the 5D calculus does not take into account certain aspects of the structure of time translations in κ-Minkowski. We propose a change of basis for the 5D calculus which leads to a more intuitive description of time translations.

From an supersymmetric electric gauge theory with the gauge group SU(N_c) × SU(N′_c) with fundamentals for each gauge group, the bifundamentals and a symmetric flavor and a conjugate symmetric flavor for SU(N_c), we apply Seiberg dual to each gauge group independently and obtain two supersymmetric dual magnetic gauge theories with dual matters including the gauge singlets. By analyzing the F-term equations of the dual magnetic superpotentials, we describe the intersecting brane configurations of type IIA string theory corresponding to the meta-stable nonsupersymmetric vacua of these gauge theories. The case where the above symmetric flavor is replaced by an antisymmetric flavor is also discussed.

We construct the type IIA nonsupersymmetric meta-stable brane configuration consisting of (2k+1) NS5-branes and D4-branes where the electric gauge theory superpotential has an order (2k+2) polynomial for the bifundamentals. We find a rich pattern of nonsupersymmetric meta-stable states as well as the supersymmetric stable ones. By adding the orientifold 4-plane to this brane configuration, we also describe the intersecting brane configuration of type IIA string theory corresponding to the meta-stable nonsupersymmetric vacua of corresponding gauge theory.

We developed a new and simple approximation scheme for centrifugal term. Using the new approximate formula for 1/r² we derived approximately analytical solutions to the radial Schrödinger equation of the Hulthén potential with arbitrary l-states. Normalized analytical wave-functions are also obtained. Some energy eigenvalues are numerically calculated and compared with those obtained by C. S. Jia et al. and other methods such as the asymptotic iteration, the supersymmetry, the numerical integration methods and a Mathematica program, schroedinger, by W. Lucha and F. F. Schöberl.