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A. B. Balantekin

Publications and source records attributed to A. B. Balantekin.

At least 199 records · Page 11Linked to original sources
arXiv2003

Do the KamLAND and Solar Neutrino Data Rule out Solar Density Fluctuations?

We elucidate effects of solar density fluctuations on neutrino propagation through the Sun. Using data from the recent solar neutrino and KamLAND experiments we provide stringent limits on solar density fluctuations. It is shown that the neutrino data constrains solar density fluctuations to be less than beta = 0.05 at the 70 % confidence level, where beta is the fractional fluctuation around the value given by the Standard Solar Model. We find that the best fit to the combined solar neutrino and KamLAND data is given by beta = 0.

hep-ph↗
arXiv2003

Global Analysis of Solar Neutrino and KamLAND Data

A global analysis of the data from all the solar neutrino experiments combined with the recent KamLAND data is presented. A formula frequently used in the literature gives survival probability for three active solar neutrino flavors in terms of a suitably-modified two-flavor survival probability. Corrections to this formula, which depend on $θ_{13}$ and $δm_{31}^2$, are calculated. For the mass scale suggested by the atmospheric neutrino experiments the contributions of $δm_{31}^2$ to these corrections is found to be negligible. The role of $θ_{13}$ in solar neutrino physics is elaborated. For electron neutrino oscillations into another active flavor, we find best fit values of $\tan^2 θ_{12} \sim 0.46$, $\tan^2 θ_{13} \sim 0$, and $δm_{21}^2 \sim 7.1 \times 10^{-5}$ eV$^2$. It is found that the combined solar neutrino and KamLAND date provide the limit $\cos^4 θ_{13} < 0.8$ at the 90 % confidence level.

hep-ph↗
arXiv2002

Radiation correction to astrophysical fusion reactions and the electron screening problem

We discuss the effect of electromagnetic environment on laboratory measurements of the nuclear fusion reactions of astrophysical interest. The radiation field is eliminated using the path integral formalism in order to obtain the influence functional, which we evaluate in the semi-classical approximation. We show that enhancement of the tunneling probability due to the radiation correction is extremely small and does not resolve the longstanding problem that the observed electron screening effect is significantly larger than theoretical predictions.

nucl-th↗
arXiv2002

Active-Sterile Neutrino Conversion: Consequences for the r-Process and Supernova Neutrino Detection

We examine active-sterile neutrino conversion in the late time post-core-bounce supernova environment. By including the effect of feedback on the Mikheyev-Smirnov-Wolfenstein (MSW) conversion potential, we obtain a large range of neutrino mixing parameters which produce a favorable environment for the r-process. We look at the signature of this effect in the current generation of neutrino detectors now coming on line. We also investigate the impact of the neutrino-neutrino forward scattering-induced potential on the MSW conversion.

hep-ph↗
arXiv2002

Overview of Neutrino-Nucleus Interactions

An overview of neutrino-nucleus interactions is presented. After a brief discussion of theory and applications of detector response three examples are discussed: i) Recent work on neutrino-deuteron reactions, ii) Probing strangeness content of the nucleon with neutrinos, and iii) The role of neutrino reactions in supernova dynamics and r-process nucleosynthesis.

nucl-th↗
arXiv2001

Neutrinos in Stochastic Media: From Sun to Core-Collapse Supernovae

Recent work on neutrino propagation in stochastic media and its implications for the Sun and core-collapse supernovae are reviewed. It is shown that recent results from Sudbury Neutrino Observatory and SuperKamiokande combined with a best global fit value of $δm^2= 5\times 10^{-5}$ eV$^2$ and $\tan^2 θ= 0.3$ rule out solar electron density fluctuations of a few percent or more. It is argued that solar neutrino experiments may be able to rule out even smaller fluctuations in the near future.

hep-ph↗
arXiv2001

Partition Functions in Statistical Mechanics, Symmetric Functions, and Group Representations

Partition functions for non-interacting particles are known to be symmetric functions. It is shown that powerful group-theoretical techniques can be used not only to derive these relationships, but also to significantly simplify calculation of the partition functions for particles that carry internal quantum numbers. The partition function is shown to be a sum of one or more group characters. The utility of character expansions in calculating the partition functions is explored. Several examples are given to illustrate these techniques.

cond-mat.stat-mech↗
arXiv2001

Character Expansions for the Orthogonal and Symplectic Groups

Formulas for the expansion of arbitrary invariant group functions in terms of the characters for the Sp(2N), SO(2N+1), and SO(2N) groups are derived using a combinatorial method. The method is similar to one used by Balantekin to expand group functions over the characters of the U(N) group. All three expansions have been checked for all N by using them to calculate the known expansions of the generating function of the homogeneous symmetric functions. An expansion of the exponential of the traces of group elements, appearing in the finite-volume gauge field partition functions, is worked out for the orthogonal and symplectic groups.

hep-th↗
arXiv2001

Character Expansions, Itzykson-Zuber Integrals, and the QCD Partition Function

A combinatorial formula to generate U(N) character expansions is presented. It is shown that the resulting character expansion formulas greatly simplify a number of problems where integrals over the group manifolds need to be calculated. Several examples are given, including direct and very quick calculations of the Itzykson-Zuber integral and the finite volume effective partition function of QCD in the sector with a given topological charge.

hep-th↗
arXiv2001

Supersymmetric and Shape-Invariant Generalization for Nonresonant and Intensity-Dependent Jaynes-Cummings Systems

A class of shape-invariant bound-state problems which represent transition in a two-level system introduced earlier are generalized to include arbitrary energy splittings between the two levels as well as intensity-dependent interactions. We show that the couple-channel Hamiltonians obtained correspond to the generalizations of the nonresonant and intensity-dependent nonresonant Jaynes-Cummings Hamiltonians, widely used in quantized theories of laser. In this general context, we determine the eigenstates, eigenvalues, the time evolution matrix and the population inversion matrix factor.

quant-ph↗
arXiv2000

Supersymmetric and Shape-Invariant Generalization for Non-resonant Jaynes-Cummings Systems

A class of shape-invariant bound-state problems which represent transitions in a two-level system introduced earlier are generalized to include arbitrary energy splittings between the two levels. We show that the coupled-channel Hamiltonians obtained correspond to the generalization of the non-resonant Jaynes-Cummings Hamiltonian, widely used in quantized theories of laser. In this general context, we determine the eigenstates, eigenvalues, the time evolution matrix and the population inversion matrix factor.

quant-ph↗
arXiv2000

Symplectic Symmetry of the Neutrino Mass and the See-Saw Mechanism

We investigate the algebraic structure of the most general neutrino mass Hamiltonian and place the see-saw mechanism in an algebraic framework. We show that this Hamiltonian can be written in terms of the generators of an Sp(4) algebra. The Pauli-Gursey transformation is an SU(2) rotation which is embedded in this Sp(4) group. This SU(2) also generates the see-saw mechanism.

hep-th↗
arXiv2000

Unitarity Constraints on Neutrino Mass and Mixings

We explore the implications of imposing the constraint that two neutrino flavors (which for definiteness we take to be muon and tau neutrinos) are similarly coupled to the mass basis in addition to the unitarity constraints. Implications of this scheme for specific experimental situations are discussed.

hep-ph↗
arXiv1999

Barrier Penetration for Supersymmetric Shape-Invariant Potentials

Exact reflection and transmission coefficients for supersymmetric shape-invariant potentials barriers are calculated by an analytical continuation of the asymptotic wave functions obtained via the introduction of new generalized ladder operators. The general form of the wave function is obtained by the use of the F-matrix formalism of Froman and Froman which is related to the evolution of asymptotic wave function coefficients.

quant-ph↗