675 research outputs found
Conformal Sigma Models with Anomalous Dimensions and Ricci Solitons
We present new non-Ricci-flat Kahler metrics with U(N) and O(N) isometries as
target manifolds of superconformally invariant sigma models with an anomalous
dimension. They are so-called Ricci solitons, special solutions to a Ricci-flow
equation. These metrics explicitly contain the anomalous dimension and reduce
to Ricci-flat Kahler metrics on the canonical line bundles over certain coset
spaces in the limit of vanishing anomalous dimension.Comment: 9 pages, no figure
Latent heat in the chiral phase transition
The chiral phase transition at finite temperature and density is discussed in
the framework of the QCD-like gauge field theory. The thermodynamical potential
is investigated using a variational approach. Latent heat generated in the
first-order phase transition is calculated. It is found that the latent heat is
enhanced near the tricritical point and is more than several hundred MeV per
quark.Comment: 6 pages, 3 figure
Chiral phase transition at high temperature in the QCD-like gauge theory
The chiral phase transition at high temperature is investigated using the
effect ive potential in the framework of the QCD-like gauge theory with a
variational a pproach. We have a second order phase transition at MeV.
We also investigate numerically the temperature dependence of condensate,
a nd (coefficient of the quadratic term in the effective
potential) and es timate the critical exponents of these quantities.Comment: 12 pages,7 figure
Scalar-Quark Systems and Chimera Hadrons in SU(3)_c Lattice QCD
Light scalar-quarks \phi (colored scalar particles or idealized diquarks) and
their color-singlet hadronic states are studied with quenched SU(3)_c lattice
QCD in terms of mass generation in strong interaction without chiral symmetry
breaking. We investigate ``scalar-quark mesons'' \phi^\dagger \phi and
``scalar-quark baryons'' \phi\phi\phi which are the bound states of
scalar-quarks \phi. We also investigate the bound states of scalar-quarks \phi
and quarks \psi, i.e., \phi^\dagger \psi, \psi\psi\phi and \phi\phi\psi, which
we name ``chimera hadrons''. All the new-type hadrons including \phi are found
to have a large mass even for zero bare scalar-quark mass m_\phi=0 at
a^{-1}\simeq 1GeV. We find that the constituent scalar-quark and quark picture
is satisfied for all the new-type hadrons. Namely, the mass of the new-type
hadron composed of m \phi's and n \psi's, M_{{m}\phi+{n}\psi}, satisfies
M_{{m}\phi+{n}\psi}\simeq {m} M_\phi +{n} M_\psi, where M_\phi and M_\psi are
the constituent scalar-quark and quark mass, respectively. M_\phi at m_\phi=0
estimated from these new-type hadrons is 1.5-1.6GeV, which is larger than that
of light quarks, M_\psi\simeq 400{\rm MeV}. Therefore, in the systems of
scalar-quark hadrons and chimera hadrons, scalar-quarks acquire large mass due
to large quantum corrections by gluons. Together with other evidences of mass
generations of glueballs and charmonia, we conjecture that all colored
particles generally acquire a large effective mass due to dressed gluon
effects.Comment: 9 pages, 9 figure
Non-Abelian Walls in Supersymmetric Gauge Theories
The Bogomol'nyi-Prasad-Sommerfield (BPS) multi-wall solutions are constructed
in supersymmetric U(N_C) gauge theories in five dimensions with N_F(>N_C)
hypermultiplets in the fundamental representation. Exact solutions are obtained
with full generic moduli for infinite gauge coupling and with partial moduli
for finite gauge coupling. The generic wall solutions require nontrivial
configurations for either gauge fields or off-diagonal components of adjoint
scalars depending on the gauge. Effective theories of moduli fields are
constructed as world-volume gauge theories. Nambu-Goldstone and
quasi-Nambu-Goldstone scalars are distinguished and worked out. Total moduli
space of the BPS non-Abelian walls including all topological sectors is found
to be the complex Grassmann manifold SU(N_F) / [SU(N_C) x SU(N_F-N_C) x U(1)]
endowed with a deformed metric.Comment: 62 pages, 17 figures, the final version in PR
Structure of Strange Dwarfs with Color Superconducting Core
We study effects of two-flavor color superconductivity on the structure of
strange dwarfs, which are stellar objects with similar masses and radii with
ordinary white dwarfs but stabilized by the strange quark matter core. We find
that unpaired quark matter is a good approximation to the core of strange
dwarfs.Comment: 8 pages 5 figures, J. Phys. G, accepte
Universality, the QCD critical/tricritical point and the quark number susceptibility
The quark number susceptibility near the QCD critical end-point (CEP), the
tricritical point (TCP) and the O(4) critical line at finite temperature and
quark chemical potential is investigated. Based on the universality argument
and numerical model calculations we propose a possibility that the hidden
tricritical point strongly affects the critical phenomena around the critical
end-point. We made a semi-quantitative study of the quark number susceptibility
near CEP/TCP for several quark masses on the basis of the
Cornwall-Jackiw-Tomboulis (CJT) potential for QCD in the improved-ladder
approximation. The results show that the susceptibility is enhanced in a wide
region around CEP inside which the critical exponent gradually changes from
that of CEP to that of TCP, indicating a crossover of different universality
classes.Comment: 18 pages, 10 figure
Non-trivial Infrared Structure in (2+1)-dimensional Quantum Electrodynamics
We show that the gauge-fermion interaction in multiflavour
-dimensional quantum electrodynamics with a finite infrared cut-off is
responsible for non-fermi liquid behaviour in the infrared, in the sense of
leading to the existence of a non-trivial fixed point at zero momentum, as well
as to a significant slowing down of the running of the coupling at intermediate
scales as compared with previous analyses on the subject. Both these features
constitute deviations from fermi-liquid theory. Our discussion is based on the
leading- resummed solution for the wave-function renormalization of the
Schwinger-Dyson equations . The present work completes and confirms the
expectations of an earlier work by two of the authors (I.J.R.A. and N.E.M.) on
the non-trivial infrared structure of the theory.Comment: 10 pages (LaTex), 5 figures (Postscript
Current quark mass effects on chiral phase transition of QCD in the improved ladder approximation
Current quark mass effects on the chiral phase transition of QCD is studied
in the improved ladder approximation. An infrared behavior of the gluon
propagator is modified in terms of an effective running coupling. The analysis
is based on a composite operator formalism and a variational approach. We use
the Schwinger-Dyson equation to give a ``normalization condition'' for the
Cornwall-Jackiw-Tomboulis effective potential and to isolate the ultraviolet
divergence which appears in an expression for the quark-antiquark condensate.
We study the current quark mass effects on the order parameter at zero
temperature and density. We then calculate the effective potential at finite
temperature and density and investigate the current quark mass effects on the
chiral phase transition. We find a smooth crossover for , and a
first-order phase transition for , T=0. Critical exponents are also
studied and our model gives the classical mean-field values. We also study the
temperature dependence of masses of scalar and pseudoscalar bosons. A critical
end point in the - plane is found at MeV,
MeV.Comment: 19 pages, 13 figure
Effective potential for composite operators and for an auxiliary scalar field in a Nambu-Jona-Lasinio model
We derive the effective potentials for composite operators in a
Nambu-Jona-Lasinio (NJL) model at zero and finite temperature and show that in
each case they are equivalent to the corresponding effective potentials based
on an auxiliary scalar field. The both effective potentials could lead to the
same possible spontaneous breaking and restoration of symmetries including
chiral symmetry if the momentum cutoff in the loop integrals is large enough,
and can be transformed to each other when the Schwinger-Dyson (SD) equation of
the dynamical fermion mass from the fermion-antifermion vacuum (or thermal)
condensates is used. The results also generally indicate that two effective
potentials with the same single order parameter but rather different
mathematical expressions can still be considered physically equivalent if the
SD equation corresponding to the extreme value conditions of the two potentials
have the same form.Comment: 7 pages, no figur
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