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F. C. Khanna

Publications and source records attributed to F. C. Khanna.

At least 73 records · Page 4Linked to original sources
arXiv2003

Boson Stars with Self-Interacting Quantum Scalar Fields

The Klein-Gordon-Einstein equations of classical real scalar fields have time-dependent solutions (periodic in time). We show that quantum real scalar fields can form non-oscillating (static) solitonic objects, which are quite similar to the solutions describing boson stars formed with classical and quantum complex scalar fields (the latter will be studied in this paper). We numerically analyze the difference between them concerning the mass of boson stars. On the other hand, we suggest an interesting test (a viable process that the boson star may undergo in the early universe) for the formation of boson stars. That is, it is questioned that after a second-order phase transition (a simple toy model will be considered here), what is the fate of the boson star composed of quantum real scalar field.

gr-qc↗
arXiv2003

Gauge Symmetry in Fokker-Planck dynamics

Using a Galilean metric approach, based in an embedding of the Euclidean space into a (4+1)-Minkowski space, we analyze a gauge invariant Lagrangian associated with a Riemannian manifold R, with metric g. With a specific choice of the gauge condition, the Euler-Lagrange equations are written covariantly in R, and then the Fokker-Planck equation is derived, such that the drift and the diffusion terms are obtained from g. The analysis is carried out for both, abelian and non abelian symmetries, and an example with the su(2) symmetry is presented.

hep-ph↗
arXiv2002

Properties of charmed and bottom hadrons in nuclear medium: Results for $Λ_c^+$ and $Λ_b$ hypernuclei

This reports our recent studies on changes in properties of heavy hadrons containing at least a charm or a bottom quark in nuclear matter, and that the results for the $Λ^+_c$ and $Λ_b$ hypernuclei are studied quantitatively. Comparisons are made with the results for the $Λ$ hypernuclei studied previously in the same approach. It is shown that although the scalar and vector potentials for the $Λ$, $Λ_c^+$ and $Λ_b$ in the hypernuclei multiplet with the same baryon numbers are quite similar, the wave functions obtained, e.g., for $1s_{1/2}$ state, are very different. The $Λ^+_c$ probability density distribution in $^{209}_{Λ^+_c}$Pb is much more pushed away from the center than that for the $Λ$ in $^{209}_Λ$Pb due to the Coulomb force. On the contrary, the $Λ_b$ probability density distributions in $Λ_b$ hypernuclei are much larger near the origin than those for the $Λ$ in the $Λ$ hypernuclei due to its heavy mass. A possibility of $B^-$ nuclear bound (atomic) states is also briefly discussed.

nucl-th↗
arXiv2002

$Λ^+_c$- and $Λ_b$-hypernuclei

$Λ^+_c$- and $Λ_b$-hypernuclei are studied in the quark-meson coupling (QMC) model. Comparisons are made with the results for $Λ$-hypernuclei studied in the same model previously. Although the scalar and vector potentials felt by the $Λ$, $Λ_c^+$ and $Λ_b$ in the corresponding hypernuclei multiplet which has the same baryon numbers are quite similar, the wave functions obtained, e.g., for $1s_{1/2}$ state, are very different. The $Λ^+_c$ baryon density distribution in $^{209}_{Λ^+_c}$Pb is much more pushed away from the center than that for the $Λ$ in $^{209}_Λ$Pb due to the Coulomb force. On the contrary, the $Λ_b$ baryon density distributions in $Λ_b$-hypernuclei are much larger near the origin than those for the $Λ$ in the corresponding $Λ$-hypernuclei due to its heavy mass. It is also found that level spacing for the $Λ_b$ single-particle energies is much smaller than that for the $Λ$ and $Λ^+_c$.

nucl-th↗
arXiv2002

Properties of charmed and bottom hadrons in nuclear matter: A plausible study

Changes in properties of heavy hadrons with a charm or a bottom quark are studied in nuclear matter. Effective masses (scalar potentials) for the hadrons are calculated using quark-meson coupling model. Our results also suggest that the heavy baryons containing a charm or a bottom quark will form charmed or bottom hypernuclei, which was first predicted in mid 70's. In addition a possibility of $B^-$-nuclear bound (atomic) states is briefly discussed.

nucl-th↗
arXiv2002

Generalized Bogoliubov Transformation for Confined Fields: Applications in Casimir Effect

The Bogoliubov transformation in thermofield dynamics, an operator formalism for the finite-temperature quantum-field theory, is generalized to describe a field in arbitrary confined regions of space and time. Starting with the scalar field, the approach is extended to the electromagnetic field and the energy-momentum tensor is written via the Bogoliubov transformation. In this context, the Casimir effect is calculated for zero and non-zero temperature, and therefore it can be considered as a vacuum condensation effect of the electromagnetic field. This aspect opens an interesting perspective for using this procedure as an effective scheme for calculations in the studies of confined fields, including the interacting fields.

hep-th↗
arXiv2002

Decoherence of Quantum Damped Oscillators

Quantum dissipation is studied within two model oscillators, the Caldirola-Kanai (CK) oscillator as an open system with one degree of freedom and the Bateman-Feshbach-Tikochinsky (BFT) oscillator as a closed system with two degrees of freedom. Though these oscillators describe the same classical damped motion, the CK oscillator retains the quantum coherence, whereas the damped subsystem of the BFT oscillator exhibits both quantum decoherence and classical correlation. Furthermore the amplified subsystem of the BFT oscillator shows the same degree of quantum decohernce and classical correlation.

quant-ph↗
arXiv2002

Non-Gaussian Effects on Domain Growth

The vacuum two-point function is calculated beyond the Gaussian approximation during the second order phase transition. It is found that the correlation function is dominated by the Gaussian term immediately after the phase transition but later is taken over by non-Gaussian terms as the spinodal instability continues. The non-Gaussian effects lead to larger size of domains and may imply a smaller density of topological defects than that predicted by the Hartree-Fock approximation.

hep-ph↗
arXiv2001

On radiative muon capture in hydrogen

We analyze photon spectra in the radiative muon capture in hydrogen using amplitudes derived from chiral Lagrangians. The model can describe the high energy part of the photon spectra, measured recently at TRIUMF, reasonably well.

nucl-th↗
arXiv2001

Finite temperature amplitudes and reaction rates in Thermofield dynamics

We propose a method for calculating the reaction rates and transition amplitudes of generic process taking place in a many body system in equilibrium. The relationship of the scattering and decay amplitudes as calculated in Thermo Field Dynamics the conventional techniques is established. It is shown that in many cases the calculations are relatively easy in TFD.

nucl-th↗
arXiv2001

Multiple-Scale Analysis and Renormalization of Quenched Second Order Phase Transitions

A quenched second order phase transition is modeled by an effective $Φ^4$-theory with a time-dependent Hamiltonian $\hat{H} (t)$, whose symmetry is broken spontaneously in time. The quantum field evolves out of equilibrium (nonequilibrium) during the phase transition as the density operator significantly deviates from $\hatρ (t) = e^{- β\hat{H} (t)}/Z_H$. The recently developed Liouville-von Neumann (LvN) method provides various quantum states for the phase transition in terms of a complex solution to the mean-field equation, which is equivalent to the Gaussian effective potential in the static case and to the time-dependent Hartree-Fock equation in the nonequilibrium case. Using the multiple scale perturbation theory (MSPT) we solve analytically the mean-field equation to the first order of coupling constant and find the quantum states during the quenched second order phase transition. We propose a renormalization scheme during the process of phase transition to regularize the divergences, which originate from the mode coupling between hard and hard modes or between the soft and hard modes. The effect of mode coupling is discussed.

hep-ph↗
arXiv2001

Generalized Statistics and High Tc Superconductivity

Introducing the generalized, non-extensive statistics proposed by Tsallis[1988], into the standard s-wave pairing BCS theory of superconductivity in 2D yields a reasonable description of many of the main properties of high temperature superconductors, provided some allowance is made for non-phonon mediated interactions.

cond-mat.supr-con↗
arXiv2001

On the muon capture in 28^Si and extraction of g_P

Comparison of the new data for the negative muon capture in 28^Si with the recent shell model calculations using a full 1s-0d model space and the USD empirical effective interaction and the one-nucleon weak current provides the induced pseudoscalar g_P substantially smaller than the value predicted by PCAC and pion-pole dominance. We find that adding the effect from the one-pion exchange axial charge density and using the same scheme of calculations does not change situation to the value of g_P.

nucl-th↗
arXiv2000

Screening length, dispersion relations and quark potential in thermo field dynamics

The screening length in a quark-gluon plasma, the dispersion relations of thermal gluon self-energy and the quark potential at high temperature are studied within thermo field dynamics framework. By calculation of the real and imaginary parts, of the gluon self-energy in one-loop order in thermo field dynamics, we obtain an expression for the screening length in a quark-gluon plasma and the dispersion relation between the real and imaginary parts. At high temperature, using photon exchange between electron-positron in a skeleton expansion and ladder approximation, the screened Coulomb potential is obtained, and using one-gluon and two-gluon exchange between a quark-antiquark, we get an expression for the screened quark potential up to $O(g amplitudes of generic process taking place in a many body system in equilibrium at temperature T. The relationship of the scattering and decay amplitudes as calculated in Thermo Field Dynamics to the conventional techniques is established. It is shown that in many cases the calculations are relatively easy in TFD.

hep-ph↗
arXiv2000

Electromagnetic isoscalar rho-pi-gamma exchange current and the anomalous action

Using modern data, we first refit constants needed to complete an anomalous pi-rho-omega-a_1 Lagrangian obtained within the approach of hidden local symmetries. Then we derive from this Lagrangian electromagnetic isoscalar rho-pi-gamma and rho-a_1-gamma currents needed in calculations of the deuteron electromagnetic form factors at large momentum transfers.

nucl-th↗
arXiv2000

Lepton U_l(1) symmetry and interaction of neutrinos with deuterons at high energies

The following items are discussed: 1. The lepton U_l(1) symmetry and its relation to the presence of the neutrino mass term in the Hamiltonian. 2. The possibility of the measurement of the neutrino-deuteron reactions with high energy neutrinos at SNO by using neutrinos from a neutrino factory. 3. The weak axial one-boson exchange currents for the Bethe-Salpeter equation.

nucl-th↗
arXiv2000

Generalized Invariants and Quantum Evolution of Open Fermionic System

Open systems acquire time-dependent coupling constants through interaction with an external field or environment. We generalize the Lewis-Riesenfeld invariant theorem to open system of quantum fields after second quantization. The generalized invariants and thereby the quantum evolution are found explicitly for time-dependent quadratic fermionic systems. The pair production of fermions is computed and other physical implications are discussed.

hep-th↗