6,004 research outputs found
Entropic force and entanglement system
We introduce the isothermal cavity, static holographic screen, and
accelerating surface as holographic screen to study the entropic force in the
presence of the Schwarzschild black hole. These may merge to provide a
consistent holographic screen to define the entropic force on the stretched
horizon near the event horizon. Considering the similarity between the
stretched horizon of black hole and the entanglement system, we may define the
entropic force in the entanglement system without referring the source mass.Comment: 17 pages, 2 figures, version to appear in PR
Dilute magnetic topological semiconductors: What's new beyond the physics of dilute magnetic semiconductors?
Role of localized magnetic moments in metal-insulator transitions lies at the
heart of modern condensed matter physics, for example, the mechanism of high
T superconductivity, the nature of non-Fermi liquid physics near heavy
fermion quantum criticality, the problem of metal-insulator transitions in
doped semiconductors, and etc. Dilute magnetic semiconductors have been studied
for more than twenty years, achieving spin polarized electric currents in spite
of low Curie temperatures. Replacing semiconductors with topological
insulators, we propose the problem of dilute magnetic topological
semiconductors. Increasing disorder strength which corresponds to the size
distribution of ferromagnetic clusters, we suggest a novel disordered metallic
state, where Weyl metallic islands appear to form inhomogeneous mixtures with
topological insulating phases. Performing the renormalization group analysis
combined with experimental results, we propose a phase diagram in
, where the spin-orbit coupling
controls a topological phase transition from a topological semiconductor to a
semiconductor with temperature and the distribution for ferromagnetic
clusters gives rise to a novel insulator-metal transition from either
a topological insulating or band insulating phase to an inhomogeneously
distributed Weyl metallic state with such insulating islands. Since
electromagnetic properties in Weyl metal are described by axion
electrodynamics, the role of random axion electrodynamics in transport
phenomena casts an interesting problem beyond the physics of percolation in
conventional disorder-driven metal-insulator transitions. We also discuss how
to verify such inhomogeneous mixtures based on atomic force microscopy
A topological Fermi-liquid theory for interacting Weyl metals with time reversal symmetry breaking
Introducing both Berry curvature and chiral anomaly into Landau's
Fermi-liquid theory, we construct a topological Fermi-liquid theory, applicable
to interacting Weyl metals in the absence of time reversal symmetry. Following
the Landau's Fermi-liquid theory, we obtain an effective free-energy functional
in terms of the density field of chiral fermions. The density field of chiral
fermions is determined by a self-consistent equation, minimizing the effective
free-energy functional with respect to the order-parameter field. Beyond these
thermodynamic properties, we construct Boltzmann transport theory to encode
both the Berry curvature and the chiral anomaly in the presence of forward
scattering of a Fermi-liquid state, essential for understanding dynamic
correlations in interacting Weyl metals. This generalizes the Boltzmann
transport theory for the Landau's Fermi-liquid state in the respect of
incorporating the topological structure and extends that for noninteracting
Weyl metals in the sense of introducing the forward scattering. Finally, we
justify this topological Fermi-liquid theory, generalizing the
first-quantization description for noninteracting Weyl metals into the
second-quantization representation for interacting Weyl metals. First, we
derive a topological Fermi-gas theory, integrating over high-energy electronic
degrees of freedom deep inside a pair of chiral Fermi surfaces. As a result, we
reproduce a topological Drude model with both the Berry curvature and the
chiral anomaly. Second, we take into account interactions between such
low-energy chiral fermions on the pair of chiral Fermi surfaces. We perform the
renormalization group analysis, and find that only forward scattering turns out
to be marginal above possible superconducting transition temperatures,
justifying the topological Fermi-liquid theory of interacting Weyl metals with
time reversal symmetry breaking
Nonexistence of quasinormal modes in the extremal BTZ black hole
We show that quasinormal modes cannot exist in the extremal BTZ black hole.
For this purpose, we consider propagations of a minimally coupled scalar and a
single massive graviton obtained from the cosmological topologically massive
gravity on the extremal BTZ black hole. The would-be quasinormal modes for a
scalar and graviton could not exist because it is impossible to make an ingoing
flux into the extremal (degenerate) horizon. This is consistent with the
argument that there is no propagating dynamics in the self-dual orbifold of
AdS(3) which is just the near-horizon limit of the extremal BTZ black hole.Comment: 13 pages, 2 figures, references adde
BRST quantization of a sixth-order derivative scalar field theory
We study a sixth order derivative scalar field model in Minkowski spacetime
as a toy model of higher-derivative critical gravity theories. This model is
consistently quantized when using the Becchi-Rouet-Stora-Tyutin (BRST)
quantization scheme even though it does not show gauge symmetry manifestly.
Imposing a BRST quartet generated by two scalars and ghosts, there remains a
non-trivial subspace with positive norm. This might be interpreted as a
Minkowskian dual version of the unitary truncation in the logarithmic conformal
field theory.Comment: 13 pages, 2 figures, version to appear in MPL
Entropy of black holes in topologically massive gravity
We study the issue of black hole entropy in the topologically massive
gravity. Assuming that the presence of gravitational Chern-Simons term with the
coupling does modify the horizon radius , we propose
as the Bekenstein-Hawking entropy. This
entropy of CS-BTZ black hole satisfies the first-law of thermodynamics and the
area-law but it is slightly different from the shifted-entropy based on the BTZ black hole with outer
and inner horizon . In the case of , represents
the entropy of non-rotating BTZ black hole with the Chern-Simons term
(NBTZ-CS), while reduces to the entropy of NBTZ black hole. It shows that
may be a candidate for the entropy of the CS-BTZ black hole.Comment: 11 pages, an expanded version to discuss thermodynamic aspects of
BTZ-CS and CS-BTZ black hole
Entropy function approach to charged BTZ black hole
We find solution to the metric function f(r)=0 of charged BTZ black hole
making use of the Lambert function. The condition of extremal charged BTZ black
hole is determined by a non-linear relation of M_e(Q)=Q^2(1-\ln Q^2). Then, we
study the entropy of extremal charged BTZ black hole using the entropy function
approach. It is shown that this formalism works with a proper normalization of
charge Q for charged BTZ black hole because AdS_2 x S^1 represents near-horizon
geometry of the extremal charged BTZ black hole. Finally, we introduce the
Wald's Noether formalism to reproduce the entropy of the extremal charged BTZ
black hole without normalization when using the dilaton gravity approach.Comment: 18 pages, 8 figures, version to appear in GR
Dynamical Structures of High-Frequency Financial Data
We study the dynamical behavior of high-frequency data from the Korean Stock
Price Index (KOSPI) using the movement of returns in Korean financial markets.
The dynamical behavior for a binarized series of our models is not completely
random. The conditional probability is numerically estimated from a return
series of KOSPI tick data. Non-trivial probability structures can be
constituted from binary time series of autoregressive (AR), logit, and probit
models, for which the Akaike Information Criterion shows a minimum value at the
15th order. From our results, we find that the value of the correct match ratio
for the AR model is slightly larger than the findings of other models.Comment: 4 pages, 4 figure
Black hole thermodynamics with generalized uncertainty principle
We apply the generalized uncertainty principle to the thermodynamics of a
small black hole. Here we have a black hole system with the UV cutoff. It is
shown that the minimal length induced by the GUP interrupts the
Gross-Perry-Yaffe phase transition for a small black hole. In order to see
whether the black hole remnant takes place a transition to a large black hole,
we introduce a black hole in a cavity (IR system). However, we fail to show the
phase transition of the remnant to the large black hole.Comment: 11 pages, 4 eps.figures, version to appear in PL
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