International Journal of Modern Physics A

In this talk I discuss a range of topics on developing creativity and innovation in engineering and science: the constraints on creativity and innovation such as the necessity of a fitting into the realities of the physical world; necessary personal qualities; getting a good idea in engineering and science; the art of obsession; the technology you use; and the technology of the future.

A review is presented of the current experimental status of the top quark sector of the Standard Model. The measurements summarized include searches for electroweak single top production, the latest results on the production cross-section, and searches for new physics in top quark production and decay. In addition, the recent measurement of the top quark mass to a precision of 0.7% is highlighted.

We investigate the prediction on the lepton phases in theories with a nontrivial correlation between quark (CKM) and lepton (PMNS) mixing matrices. We show that the actual evidence, under the only assumption that the correlation matrix V^M product of CKM and PMNS has a zero in the entry (1, 3), gives us a prediction for the three CP-violating invariants J, S₁ and S₂. A better determination of the lepton mixing angles will give stronger prediction for the CP-violating invariants in the lepton sector. These will be tested in the next generation experiments. To clarify how our prediction works, we show how a model based on a Grand Unified Theory and the permutation flavor symmetry S₃ predicts .

Variation of the von Neumann entropy by the Lorentz transformation is discussed. Taking the spin-singlet state in the center-of-mass frame, the von Neumann entropy in the laboratory frame is calculated from the reduced density matrix obtained by taking the trace over 4-momentum after the Lorentz transformation. As the model to discuss the EPR spin correlation, it is supposed that one parent particle splits into a superposition state of various pair states in various directions. Computing the von Neumann entropy and the Shannon entropy, we have shown a global behavior of the entropy to see a relativistic effect. We discuss also the superrelativistic limit, distinguishability between the two particles of the pair and so on.

Gravitational instabilities in a magnetized Friedman–Robertson–Walker (FRW) universe, in which the magnetic field was assumed to be too weak to destroy the isotropy of the model, are known and have been studied in the past. Accordingly, it became evident that the external magnetic field disfavors the perturbations' growth, suppressing the corresponding rate by an amount proportional to its strength. However, the spatial isotropy of the FRW universe is not compatible with the presence of large-scale magnetic fields. Therefore, in this paper we use the general-relativistic version of the (linearized) perturbed magnetohydrodynamic equations with and without resistivity, to discuss a generalized Jeans criterion and the potential formation of density condensations within a class of homogeneous and anisotropically expanding, self-gravitating, magnetized fluids in curved space–time. We find that, for a wide variety of anisotropic cosmological models, gravitomagnetic instabilities can lead to subhorizontal, magnetized condensations. In the nonresistive case, the power spectrum of the unstable cosmological perturbations suggests that most of the power is concentrated on large scales (small k), very close to the horizon. On the other hand, in a resistive medium, the critical wave-numbers so obtained, exhibit a delicate dependence on resistivity, resulting in the reduction of the corresponding Jeans lengths to smaller scales (well bellow the horizon) than the nonresistive ones, while increasing the range of cosmological models which admit such an instability.

We construct the thermal boundary states from the type IIB Green–Schwarz superstring in pp-wave background in the light-cone gauge. The superstring is treated in the canonical ensemble and in the TFD formalism which is appropriate to discuss canonically quantized systems. The thermal boundary states are obtained by thermalizing the total boundary states which are the boundary states of the total system that is composed by the superstring modes and the corresponding thermal reservoir modes. That analysis is similar to the one in the flat space–time case.⁶⁷ However, there are some subtleties concerning the construction of the total string which are discussed. Next, we compute the entropy of thermal boundary state which is defined as the expectation value of the superstring entropy operator in the thermal boundary state.

We applied the factorization method to the processes of two-particle scattering with an unstable particle in the intermediate state. It was shown, that in the framework of this method, the cross-section can be represented in the universal factorized form for an arbitrary set of particles. An exact factorization is caused by a specific structure of unstable particles propagators. Phenomenological analysis of the factorization effect is performed.

The development of the Wess–Zumino action or one-cycle is reviewed from the path integral approach. This is related to the occurrence of anomalies in the theory, and generally signifies a breakdown of gauge invariance. The Jackiw–Rajaraman version of the chiral Schwinger model is studied by means of path integrals. It is shown how the model can be made gauge invariant by using a Wess–Zumino term to write a gauge invariant Lagrangian. The model is considered only in bosonized form without any reference to fermions. The constraints are determined. These components are then used to write a path integral quantization for the bosonized form of the model. Some physical quantities and information, in particular, propagators are derived from the path integral.

Heavy multiquark potential in the SU(N) color group using hard-wall AdS/QCD at both zero and finite temperature is studied. A Cornell-like potential is obtained for baryons and other exotic configurations and compared with those in the quenched lattice calculation in N = 3 case. At the end we also discuss possible improvements in the UV region of potential.

We perform a Monte Carlo study of the lattice two-dimensional gauged XY-model. Our results confirm the strong-coupling expansion arguments that for sufficiently small values of the spin–spin coupling the "gauge symmetry breaking" terms decouple and the long-distance physics is that of the unbroken pure gauge theory. We find no evidence for the existence, conjectured earlier, of massless states near a critical value of the spin–spin coupling. We comment on recent remarks in the literature on the use of gauged XY-models in proposed constructions of chiral lattice gauge theories.

We consider a universal mass matrix model which has a seesaw-invariant structure with the most general texture based on flavor 2 ↔ 3 symmetry common to all quarks and leptons. The CKM quark mixing matrix of the model is analyzed. It is shown that the model is consistent with all the experimental data of quark mixings by tuning free parameters of the model. We also show that the values of parameters of the present model consistent with the experimental data are not far from the ones of the mass matrix model with a vanishing (1, 1) element.

In this paper, we elaborate the problem of energy–momentum in general relativity by energy–momentum prescriptions theory. Our aim is to calculate energy and momentum densities for the general form of gravitational waves. In this connection, we have extended the previous works by using the prescriptions of Bergmann and Tolman. It is shown that they are finite and reasonable. In addition, using Tolman prescription, exactly, leads to the same results that have been obtained by Einstein and Papapetrou prescriptions.

As toy models for space–time at the Planck scale, we consider examples of fermion systems in discrete space–time which are composed of one or two particles defined on two up to nine space–time points. We study the self-organization of the particles as described by a variational principle both analytically and numerically. We find an effect of spontaneous symmetry breaking which leads to the emergence of a discrete causal structure.

In this paper, we calculate the electromagnetic form-factor of the π meson with the light-cone QCD sum rules. The numerical value is in excellent agreement with the experimental data (extrapolated to the limit of zero momentum transfer or the normalization condition F_π(0) = 1). For large momentum transfers, the values from the two sum rules are all comparable with the experimental data and theoretical estimations.