57,526 research outputs found
The Pion Velocity at Chiral Restoration and the Vector Manifestation
We study the effects of Lorentz non-invariance on the physical pion velocity
at the critical temperature in an effective theory of hidden local
symmetry (HLS) with the "vector manifestation" fixed point. We match at a
"matching scale" the axial-vector current correlator in the HLS
with the one in the operator product expansion for QCD, and present the
matching condition to determine the bare pion velocity. We find that the
physical pion velocity, which is found to be one at when starting from
the Lorentz invariant bare HLS, remains close to one with the Lorentz
non-invariance, . This result is quite similar to
the pion velocity in dense matter.Comment: 13 pages, discussions for clarifying the matching procedure are adde
Effective Degrees of Freedom at Chiral Restoration and the Vector Manifestation in HLS theory
The question as to what the relevant effective degrees of freedom at the
chiral phase transition are remains largely unanswered and must be addressed in
confronting both terrestrial and space laboratory observations purporting to
probe matter under extreme conditions. We address this question in terms of the
vector susceptibility \chi_V (VSUS in short) and the axial-vector
susceptibility \chi_A (ASUS in short) at the temperature-induced chiral
transition. We consider two possible, albeit simplified, cases that are
contrasting, one that is given by the standard chiral theory where only the
pions figure in the vicinity of the transition and the other that is described
by hidden local symmetry (HLS) theory with the Harada-Yamawaki vector
manifestation (VM) where nearly massless vector mesons also enter. We find that
while in the standard chiral theory, the pion velocity v_\pi proportional to
the ratio of the space component f_\pi^s of the pion decay constant over the
time component f_\pi^t tends to zero near chiral restoration with f_\pi^t\neq
0, in the presence of the vector mesons with vanishing mass, the result is
drastically different: HLS with VM {\it predicts} that \chi_V automatically
equals \chi_A in consistency with chiral invariance and that v_\pi\sim 1f_\pi^t\approx f_\pi^s\to 0 as T\to T_c. These results are obtained in the
leading order in power counting but we expect their qualitative features to
remain valid more generally in the chiral limit thanks to the VM point.Comment: 32 pages, 2 figure
Discrimination of -nucleus potentials in the angular distribution of elastic scattering of hyperons from nuclei
We theoretically investigate the elastic scattering of 50-MeV
hyperons from Si and Pb in order to clarify the radial
distribution of -nucleus (optical) potentials. The angular
distributions of differential cross sections are calculated using several
potentials that can explain experimental data of the atomic X-ray
and (, ) reaction spectra simultaneously. The magnitude and
oscillation pattern of the angular distributions are understood by the use of
nearside/farside decompositions of their scattering amplitudes. It is shown
that the resultant angular distributions can considerably discriminate among
the radial distributions of the potentials that have a repulsion inside the
nuclear surface and an attraction outside the nucleus with a sizable
absorption
Entanglement branching operator
We introduce an entanglement branching operator to split a composite
entanglement flow in a tensor network which is a promising theoretical tool for
many-body systems. We can optimize an entanglement branching operator by
solving a minimization problem based on squeezing operators. The entanglement
branching is a new useful operation to manipulate a tensor network. For
example, finding a particular entanglement structure by an entanglement
branching operator, we can improve a higher-order tensor renormalization group
method to catch a proper renormalization flow in a tensor network space. This
new method yields a new type of tensor network states. The second example is a
many-body decomposition of a tensor by using an entanglement branching
operator. We can use it for a perfect disentangling among tensors. Applying a
many-body decomposition recursively, we conceptually derive projected entangled
pair states from quantum states that satisfy the area law of entanglement
entropy.Comment: 11 pages, 13 figure
Vector Manifestation in Hot and/or Dense Matter
In this talk I summarize main features of the vector manifestation (VM) which
was recently proposed as a novel manifestation of the Wigner realization of
chiral symmetry in which the symmetry is restored at the critical point by the
massless degenerate pion (and its flavor partners) and the rho meson (and its
flavor partners) as the chiral partner. I show how the VM is realized in hot
and dense QCD using the effective field theory of QCD based on the hidden local
symmetry.Comment: Talk given at YITP-RCNP Workshop ``Chiral Restoration in Nuclear
Medium'' (October 7-9,2002). 12 pages, PTPTe
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