International Journal of Modern Physics A

Neutrino masses originate most likely at some high energy scale M≫M_Z. To obtain reliable predictions for neutrino masses and mixing angles one has to take into account quantum corrections which, in cases of degenerate or partly degenerate neutrino spectra, can significantly change the pattern of the mixing angles. We review the calculation of these quantum corrections in the case in which the neutrino masses are effectively described by the single dimension 5 operator. In the framework of the Standard Model or its minimal supersymmetric extension we discuss both the corrections described by the renormalization group equations (RGE) and the low energy threshold corrections. We emphasize that the infrared fixed points of the RGE predict a relation between the mixing angles which is incompatible with the presently favoured LMA solution to the solar neutrino problem. We also show that in the MSSM the threshold corrections can lead to qualitatively different predictions for the mixing angles.

The calculations of the extended knot families and to satisfy the diffeomorphism constraint, Hamiltonian constraint and Mandelstam identities are given in the extended loop representation.

We introduce the "chain-by-chain" method for constructing the constraint structure of a system possessing both first- and second-class constraints. We show that the whole constraint can be classified into completely irreducible first- or second-class chains. We found an appropriate redefinition of second-class constraints to obtain a symplectic algebra among them.

Six different models, straightforward extensions of the standard model to of SU(3)_c ⊗ SU(3)_L ⊗ U(1)_X, which do not contain particles with exotic electric charges are presented. Two of the models are one family and four are three family models. In two of the three family models one of the families transforms different from the others, and in the other two all the three families are different.

We herein construct a Heisenberg-like algebra for the one-dimensional quantum free Klein–Gordon equation defined on the interval of the real line of length L. Using the realization of the ladder operators of this Heisenberg-type algebra in terms of physical operators we build a (3+1)-dimensional free quantum field theory based on this algebra. We introduce fields written in terms of the ladder operators of this Heisenberg-type algebra and a free quantum Hamiltonian in terms of these fields. The mass spectrum of the physical excitations of this quantum field theory is given by , where n=1,2,… and m_q is the mass of a particle in a relativistic infinite square-well potential of width L.

The effect of limiting the acceptance in rapidity on event-by-event multiplicity fluctuations in nucleus–nucleus collisions has been investigated. Our analysis shows that the multiplicity fluctuations decrease when the rapidity acceptance is decreased. We explain this trend by assuming that the probability distribution of the particles in the smaller acceptance window follows binomial distribution. Following a simple statistical analysis, we conclude that the event-by-event multiplicity fluctuations for full acceptance are likely to be larger than those observed in the experiments, since the experiments usually have detectors with limited acceptance. We discuss the application of our model to simulated data generated using VENUS, a widely used event generator in heavy-ion collisions. We also discuss the results from our calculations in the presence of dynamical fluctuations and possible observation of these in the actual data.

We write the renormalization group equation for the Higgs mass m_H and use it to improve calculations of m_H in the standard model. This improvement changes the results considerably and should be taken into account in a reliable calculation. Our numerical results give the upper bound m_H≤173 GeV under the condition that the effective potential is real at its absolute minimum. This result is in agreement with recent experimental and theoretical estimates.

We derive a new Weyl ordering operator formula which recasts given operators into Weyl ordering. In so doing, the Weyl ordering formulation of the entangled state representation is obtained, which turns out to be the Weyl ordered Dirac δ-operator functions. The Weyl ordering of the Wigner operator and squeezing operator in entangled state representation are also deduced.