10,024 research outputs found
Comment on ``Confirmation of the Sigma Meson''
We comment on the recent paper by N.A. Tornqvist and M. Roos published in
Phys. Rev. Lett. 76, 1575 (1996).Comment: 3 pages (LaTeX), 1 PostScript Figur
Effective Theory Approach to the Skyrme model and Application to Pentaquarks
The Skyrme model is reconsidered from an effective theory point of view. From
the most general chiral Lagrangian up to including terms of order ,
and (), new interactions, which have never
been considered before, appear upon collective coordinate quantization. We
obtain the parameter set best fitted to the observed low-lying baryon masses,
by performing the second order perturbative calculations with respect to
. We calculate the masses and the decay widths of the other members
of (mainly) anti-decuplet pentaquark states. The formula for the decay widths
is reconsidered and its baryon mass dependence is clarified.Comment: 65 pages, 1 figure. Revised version:the complete second order
perturbative calculations performed and two appendices adde
Chiral Doubling of Heavy-Light Hadrons and the Vector Manifestation of Hidden Local Symmetry
Starting with a hidden local symmetry Lagrangian at the vector manifestation
(VM) fixed point that incorporates heavy-quark symmetry and matching the bare
theory to QCD, we calculate the splitting of chiral doublers of heavy-light
mesons proposed by Nowak, Rho and Zahed, and Bardeen and Hill. We show, in the
three-flavor chiral limit, that the splitting is directly proportional to the
light-quark condensate and comes out to be \sim (1/3) m_N where m_N
is the nucleon mass, implying that the splitting vanishes in the chiral limit
at the chiral restoration point -- temperature T_c, density n_c or number of
flavors N_F^c. The result turns out to be surprisingly simple with the vector
(\rho) meson playing the crucial role in quantum corrections, pointing to the
relevance of the VM to QCD in the way chiral symmetry is manifested in hadronic
matter. We also make predictions on the hadronic decay processes of the excited
heavy (charm) -light mesons \tilde{D}.Comment: 28 pages, 3 figure, sectionalized, added several new analyses
including an analysis on the decay processes of excited heavy meson
A Reversibility Parameter for a Markovian Stepper
Recent experimental studies on the stepwize motion of biological molecular
motors have revealed that the ``characteristic distance'' of a step is usually
less than the actual step size. This observation implies that the
detailed-balance condition for kinetic rates of steps is violated in these
motors. In this letter, in order to clarify the significance of the
characteristic distance, we study a Langevin model of a molecular motor with a
hidden degree of freedom. We find that the ratio of the characteristic distance
to the step size is equal to unity if the dominant paths in the state space are
one dimensional, while it deviates from unity if the dominant paths are
branched. Therefore, this parameter can be utilized to determine the
reversibility of a motor even under a restricted observation.Comment: 6 pages, 2 figures - minor revision
Is there a black hole minimum mass?
Applying the first and generalised second laws of thermodynamics for a
realistic process of near critical black hole formation, we derive an entropy
bound, which is identical to Bekenstein's one for radiation. Relying upon this
bound, we derive an absolute minimum mass ,
where and is the effective degrees of freedom for the
initial temparature and the Planck mass, respectively. Since this minimum mass
coincides with the lower bound on masses of which black holes can be regarded
as classical against the Hawking evaporation, the thermodynamical argument will
not prohibit the formation of the smallest classical black hole. For more
general situations, we derive a minimum mass, which may depend on the initial
value for entropy per particle. For primordial black holes, however, we show
that this minimum mass can not be much greater than the Planck mass at any
formation epoch of the Universe, as long as is within a reasonable
range. We also derive a size-independent upper bound on the entropy density of
a stiff fluid in terms of the energy density.Comment: 4 pages, accepted for publication in Physical Review D, minor
correctio
Exact transformation of a Langevin equation to a fluctuating response equation
We demonstrate that a Langevin equation that describes the motion of a
Brownian particle under non-equilibrium conditions can be exactly transformed
to a special equation that explicitly exhibits the response of the velocity to
a time dependent perturbation. This transformation is constructed on the basis
of an operator formulation originally used in nonlinear perturbation theory for
differential equations by extending it to stochastic analysis. We find that the
obtained expression is useful for the calculation of fundamental quantities of
the system, and that it provides a physical basis for the decomposition of the
forces in the Langevin description into effective driving, dissipative, and
random forces in a large-scale description.Comment: 14 pages, to appear in J. Phys. A: Math. Ge
Coarse-grained loop algorithms for Monte Carlo simulation of quantum spin systems
Recently, Syljuasen and Sandvik proposed a new framework for constructing
algorithms of quantum Monte Carlo simulation. While it includes new classes of
powerful algorithms, it is not straightforward to find an efficient algorithm
for a given model. Based on their framework, we propose an algorithm that is a
natural extension of the conventional loop algorithm with the split-spin
representation. A complete table of the vertex density and the worm-scattering
probability is presented for the general XXZ model of an arbitrary S with a
uniform magnetic field.Comment: 12 pages, 7 figures, insert a word "squared" in the first line of the
caption of Fig.7 and correct the label of vertical axis of Fig.
Stochastic series expansion algorithm for the S=1/2 XY model with four-site ring exchange
We describe a stochastic series expansion (SSE) quantum Monte Carlo method
for a two-dimensional S=1/2 XY-model (or, equivalently, hard-core bosons at
half-filling) which in addition to the standard pair interaction J includes a
four-particle term K that flips spins on a square plaquette. The model has
three ordered ground state phases; for K/J<8 it has long-range xy spin order
(superfluid bosons), for K/J>15 it has staggered spin order in the z direction
(charge-density-wave), and between these phases it is in a state with columnar
order in the bond and plaquette energy densities. We discuss an implementation
of directed-loop updates for the SSE simulations of this model and also
introduce a "multi-branch" cluster update which significantly reduces the
autocorrelation times for large K/J. In addition to the pure J-K model, which
in the z basis has only off-diagonal terms, we also discuss modifications of
the algorithm needed when various diagonal interactions are included.Comment: 23 pages, 21 figure
Conformal Phase Transition and Fate of the Hidden Local Symmetry in Large N_f QCD
It is observed that the Hidden Local Symmetry (HLS) for the vector mesons in
the ordinary QCD with smaller N_f plays the role of the "Higgsed magnetic gauge
symmetry" for the Seiberg duality in the SUSY QCD. For large N_f where the
conformal phase transition with chiral restoration and deconfinement is
expected to take place, we find that the HLS model also exhibits the chiral
restoration by the loop corrections (including the quadratic divergence) in a
manner similar to that in the CP^{N-1} model, provided that the bare HLS
Lagrangian respects the Georgi's vector limit at a certain N_f (\approx 7).Comment: 4 Pages (RevTeX), 3 PS figures are included Minor corrections are
made for the introductory part. This is the version to appear in Physical
Review Letter
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