2,407 research outputs found
Squeezed Neutrino Oscillations in Quantum Field Theory
By resorting to recent results on fermion mixing which show that the Fock
space of definite flavor states is unitarily inequivalent to the Fock space of
definite mass states, we discuss the phenomenological implications on the
neutrino oscillation formula. For finite momentum the oscillation amplitude is
depressed, or "squeezed", by a momentum dependent factor. In the relativistic
limit the conventional oscillation formula is recovered.Comment: 12 pages, LaTex, 1 figure ( on request ), in press on Phys. Lett. B.
(minor changes: reformatted
Spectral properties of a spin-incoherent Luttinger Liquid
We present time-dependent density matrix renormalization group (DMRG) results
for strongly interacting one dimensional fermionic systems at finite
temperature. When interactions are strong the characteristic spin energy can be
greatly suppressed relative to the characteristic charge energy, allowing for
the possibility of spin-incoherent Luttinger liquid physics when the
temperature is high compared to the spin energy, but small compared to the
charge energy. Using DMRG we compute the spectral properties of the model
at arbitrary temperatures with respect to both spin and charge energies. We
study the full crossover from the Luttinger liquid regime to the
spin-incoherent regime,focusing on small , where the signatures of
spin-incoherent behavior are more manifest. Our method allows us to access the
analytically intractable regime where temperature is of the order of the spin
energy, . Our results should be helpful in the interpretation of
experiments that may be in the crossover regime, , and apply to
one-dimensional cold atomic gases where finite-temperature effects are
appreciable. The technique may also be used to guide the development of
analytical approximations for the crossover regime.Comment: 7 pages, 5 figure
Color superconducting 2SC+s quark matter and gapless modes at finite temperatures
We investigate the phase diagram of color superconducting quark matter with
strange quarks (2SC+s quark matter) in beta equliibrium at zero as well as
finite temperatures within a Nambu-Jona-Lasinio model. The variational method
as used here allows us to investigate simultaneous formation of condensates in
quark--antiquark as well as in diquark channels. Color and electric charge
neutrality conditions are imposed in the calculation of the thermodynamic
potential. Medium dependance of strange quark mass plays a sensitve role in
maintaining charge neutrality conditions. At zero temperature the system goes
from gapless phase to usual BCS phase through an intermediate normal phase as
density is increased. The gapless modes show a smooth behaviour with respect to
temperature vanishing above a critical temperature which is larger than the BCS
transition temperature. We observe a sharp transition from gapless
superconducting phase to the BCS phase as density is increased for the color
neutral matter at zero temperature. As temperature is increased this however
becomes a smooth transition.Comment: 18 pages, 14 figure
STUDY ON DEVELOPMENTS OF BODY COMPOSITION AND PHYSICAL FITNESS FOR A YEAR IN JAPANESE ADOLESCENT TRACK AND FIELD ATHLETES
It is well known that physical fitness develops with the increased muscle thickness in adolescent boys especially from 16 to 18 years. Fukunaga et al. (1989) investigated the developments of body composition in Japanese boys and girls, and revealed that the muscle and fat cross sectional area increased with age from 16 to 18 years. Seefeldt et al. (1986) had reported that vertical jump height and maximal running velocity improved linearly with age from 5 to 18 years in boys who had no habitual physical training. However, no studies have investigated development of physical fitness of adolescent athletes. In addition, duration of measurement of longitudinal studies was a year basically. It is necessary to assess physical fitness several times within a year.The purpose of this study was to investigate developments of body composition and physical fitness in Japanese adolescent track and field athletes
Noncommutative Thermofield Dynamics
The real-time operator formalism for thermal quantum field theories,
thermofield dynamics, is formulated in terms of a path-integral approach in
non-commutative spaces. As an application, the two-point function for a thermal
non-commutative theory is derived at the one-loop level. The
effect of temperature and the non-commutative parameter, competing with one
another, is analyzed.Comment: 13 pages; to be published in IJMP-A
TFD Approach to Bosonic Strings and -branes
In this work we explain the construction of the thermal vacuum for the
bosonic string, as well that of the thermal boundary state interpreted as a
-brane at finite temperature. In both case we calculate the respective
entropy using the entropy operator of the Thermo Field Dynamics Theory. We show
that the contribution of the thermal string entropy is explicitly present in
the -brane entropy. Furthermore, we show that the Thermo Field approach
is suitable to introduce temperature in boundary states.Comment: 6 pages, revtex, typos are corrected. Prepared for the Second
Londrina Winter School-Mathematical Methods in Physics, August 25-30, 2002,
Londrina-Pr, Brazil. To appear in a special issue of IJMP
The unmasking of thermal Goldstone bosons
The problem of extracting the modes of Goldstone bosons from a thermal
background is reconsidered in the framework of relativistic quantum field
theory. It is shown that in the case of spontaneous breakdown of an internal
bosonic symmetry a recently established decomposition of thermal correlation
functions contains certain specific contributions which can be attributed to a
particle of zero mass.Comment: 7 pages, LaTeX; new and considerably strengthened results after Eq.
(14); to appear in Phys. Rev.
Two-Dimensional Order and Disorder Thermofields
The main objective of this paper was to obtain the two-dimensional order and
disorder thermal operators using the Thermofield Bosonization formalism. We
show that the general property of the two-dimensional world according with the
bosonized Fermi field at zero temperature can be constructed as a product of an
order and a disorder variables which satisfy a dual field algebra holds at
finite temperature. The general correlation functions of the order and disorder
thermofields are obtained.Comment: 4 page
Finite Temperature Density Matrix Renormalization using an enlarged Hilbert space
We apply a generalization of the time-dependent DMRG to study finite
temperature properties of several quantum spin chains, including the frustrated
model. We discuss several practical issues with the method, including
use of quantum numbers and finite size effects. We compare with transfer-matrix
DMRG, finding that both methods produce excellent results.Comment: 4 pages and 4 figure
Maximum Entanglement in Squeezed Boson and Fermion States
A class of squeezed boson and fermion states is studied with particular
emphasis on the nature of entanglement. We first investigate the case of
bosons, considering two-mode squeezed states. Then we construct the fermion
version to show that such states are maximum entangled, for both bosons and
fermions. To achieve these results, we demonstrate some relations involving
squeezed boson states. The generalization to the case of fermions is made by
using Grassmann variables.Comment: 4 page
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