17,094 research outputs found
T/B scaling without quasiparticle mass divergence: YbCo2Ge4
YbCoGe is a clean paramagnetic Kondo lattice which displays non-Fermi
liquid behavior. We report a detailed investigation of the specific heat,
magnetic Gr\"uneisen parameter () and temperature derivative
of the magnetization () on a high-quality single crystal at temperatures
down to ~K and magnetic fields up to 7~T. and
display a divergence upon cooling and obey scaling. Similar behavior has
previously been found in several other Yb-based Kondo lattices and related to a
zero-field quantum critical point without fine tuning of pressure or
composition. However, in the approach of the electronic heat
capacity coefficient of YbCoGe saturates at low , excluding
ferromagnetic quantum criticality. This indicates that scaling is
insufficient to prove a zero-field quantum critical point.Comment: 6 pages, 6 figures (including supplemental material
Dynamics of Gravitating Magnetic Monopoles
According to previous work on magnetic monopoles, static regular solutions
are nonexistent if the vacuum expectation value of the Higgs field is
larger than a critical value , which is of the order of the
Planck mass. In order to understand the properties of monopoles for
, we investigate their dynamics numerically. If is
large enough (), a monopole expands exponentially and a
wormhole structure appears around it, regardless of coupling constants and
initial configuration. If is around , there are three
types of solutions, depending on coupling constants and initial configuration:
a monopole either expands as stated above, collapses into a black hole, or
comes to take a stable configuration.Comment: 11 pages, revtex, postscript figures; results for various initial
conditions are added; to appear in Phys. Rev.
A Hybrid Model for QCD Deconfining Phase Boundary
Intensive search for a proper and realistic equations of state (EOS) is still
continued for studying the phase diagram existing between quark gluon plasma
(QGP) and hadron gas (HG) phases. Lattice calculations provide such EOS for the
strongly interacting matter at finite temperature () and vanishing baryon
chemical potential (). These calculations are of limited use at finite
due to the appearance of notorious sign problem. In the recent past,
we had constructed a hybrid model description for the QGP as well as HG phases
where we make use of a new excluded-volume model for HG and a
thermodynamically-consistent quasiparticle model for the QGP phase and used
them further to get QCD phase boundary and a critical point. Since then many
lattice calculations have appeared showing various thermal and transport
properties of QCD matter at finite and . We test our hybrid
model by reproducing the entire data for strongly interacting matter and
predict our results at finite so that they can be tested in future.
Finally we demonstrate the utility of the model in fixing the precise location,
the order of the phase transition and the nature of CP existing on the QCD
phase diagram. We thus emphasize the suitability of the hybrid model as
formulated here in providing a realistic EOS for the strongly interacting
matter.Comment: 22 pages, 10 figures. corrected version published in Physical Review
D. arXiv admin note: substantial text overlap with arXiv:1201.044
Transport Coefficients of Gluon Plasma
Transport coefficients of gluon plasma are calculated for a SU(3) pure gauge
model by lattice QCD simulations on and
lattices. Simulations are carried out at a slightly above the deconfinement
transition temperature , where a new state of matter is currently being
pursued in RHIC experiments. Our results show that the ratio of the shear
viscosity to the entropy is less than one and the bulk viscosity is consistent
with zero in the region, .Comment: 10 pages, Late
Effect of Applied Orthorhombic Lattice Distortion on the Antiferromagnetic Phase of CeAuSb
We study the response of the antiferromagnetism of CeAuSb to orthorhombic
lattice distortion applied through in-plane uniaxial pressure. The response to
pressure applied along a lattice direction shows a
first-order transition at zero pressure, which shows that the magnetic order
lifts the symmetry of the unstressed lattice. Sufficient
pressure appears to rotate the principal axes of the
order from to . At low pressure, the transition at is weakly first-order, however it
becomes continuous above a threshold pressure. We discuss
the possibility that this behavior is driven by order parameter fluctuations,
with the restoration of a continuous transition a result of reducing the
point-group symmetry of the lattice.Comment: 6 pages, 7 figure
Magnetized Domain Walls in the Deconfined Sakai-Sugimoto Model at Finite Baryon Density
The magnetized pure pion gradient () phase in the deconfined
Sakai-Sugimoto model is explored at zero and finite temperature. We found that
the temperature has very small effects on the phase. The thermodynamical
properties of the phase shows that the excitations behave like a scalar
solitonic free particles. By comparing the free energy of the pion gradient
phase to the competing multiquark-pion gradient (MQ-) phase,
it becomes apparent that the pure pion gradient is less thermodynamically
preferred than the MQ- phase. However, in the parameter space
where the baryonic chemical potential is smaller than the onset value of the
multiquark, the dominating magnetized nuclear matter is the pion gradient
phase.Comment: 20 pages, 9 figure
Numerical Renormalization Group Study of non-Fermi-liquid State on Dilute Uranium Systems
We investigate the non-Fermi-liquid (NFL) behavior of the impurity Anderson
model (IAM) with non-Kramers doublet ground state of the f configuration
under the tetragonal crystalline electric field (CEF). The low energy spectrum
is explained by a combination of the NFL and the local-Fermi-liquid parts which
are independent with each other. The NFL part of the spectrum has the same form
to that of two-channel-Kondo model (TCKM). We have a parameter range that the
IAM shows the divergence of the magnetic susceptibility together with
the positive magneto resistance. We point out a possibility that the anomalous
properties of UThRuSi including the decreasing resistivity
with decreasing temperature can be explained by the NFL scenario of the TCKM
type. We also investigate an effect of the lowering of the crystal symmetry. It
breaks the NFL behavior at around the temperature, , where
is the orthorhombic CEF splitting. The NFL behavior is still expected above the
temperature, .Comment: 25 pages, 12 figure
Sequence of Potentials Lying Between the U(5) and X(5) Symmetries
Starting from the original collective Hamiltonian of Bohr and separating the
beta and gamma variables as in the X(5) model of Iachello, an exactly soluble
model corresponding to a harmonic oscillator potential in the beta-variable (to
be called X(5)-) is constructed. Furthermore, it is proved that the
potentials of the form (with n being integer) provide a ``bridge''
between this new X(5)- model (occuring for n=1) and the X(5) model
(corresponding to an infinite well potential in the beta-variable, materialized
for n going to infinity. Parameter-free (up to overall scale factors)
predictions for spectra and B(E2) transition rates are given for the potentials
, , , , corresponding to E(4)/E(2) ratios
of 2.646, 2.769, 2.824, and 2.852 respectively, compared to the E(4)/E(2)
ratios of 2.000 for U(5) and 2.904 for X(5). Hints about nuclei showing this
behaviour, as well as about potentials ``bridging'' the X(5) symmetry with
SU(3) are briefly discussed.Comment: 18 pages, LaTeX, 5 postscript figure
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