8,643 research outputs found

### Microstates of black holes in expanding universe from interacting branes

Thermodynamics of the near extremal black p-branes can be described by
collective motions of gravitationally interacting branes. This proposal is
called the p-soup model. In this paper, we check this proposal in the case of
black brane system which is asymptotically Friedmann-Lemaitre-Robertson-Walker
universe in an infinite distance. As a result, we can show that the
gravitationally interacting branes explain free energy, entropy, temperature
and other physical quantities in these systems. This implies that the
microstates of this kind of brane system can be also understood in the p-soup
model.Comment: 18 page

### Entanglement Entropy of Disjoint Regions in Excited States : An Operator Method

We develop the computational method of entanglement entropy based on the idea
that $Tr\rho_{\Omega}^n$ is written as the expectation value of the local
operator, where $\rho_{\Omega}$ is a density matrix of the subsystem $\Omega$.
We apply it to consider the mutual Renyi information
$I^{(n)}(A,B)=S^{(n)}_A+S^{(n)}_B-S^{(n)}_{A\cup B}$ of disjoint compact
spatial regions $A$ and $B$ in the locally excited states defined by acting the
local operators at $A$ and $B$ on the vacuum of a $(d+1)$-dimensional field
theory, in the limit when the separation $r$ between $A$ and $B$ is much
greater than their sizes $R_{A,B}$. For the general QFT which has a mass gap,
we compute $I^{(n)}(A,B)$ explicitly and find that this result is interpreted
in terms of an entangled state in quantum mechanics. For a free massless scalar
field, we show that for some classes of excited states,
$I^{(n)}(A,B)-I^{(n)}(A,B)|_{r \rightarrow \infty} =C^{(n)}_{AB}/r^{\alpha
(d-1)}$ where $\alpha=1$ or 2 which is determined by the property of the local
operators under the transformation $\phi \rightarrow -\phi$ and $\alpha=2$ for
the vacuum state. We give a method to compute $C^{(2)}_{AB}$ systematically.Comment: 22 pages; v3, typos corrected, published versio

### Half-magnetization plateau stabilized by structural distortion in the antiferromagnetic Heisenberg model on a pyrochlore lattice

Magnetization plateaus, visible as anomalies in magnetic susceptibility at
low temperatures, are one of the hallmarks of frustrated magnetism. We show how
an extremely robust half-magnetization plateau can arise from coupling between
spin and lattice degrees of freedom in a pyrochlore antiferromagnet, and
develop a detailed symmetry of analysis of the simplest possible scenario for
such a plateau state. The application of this theory to the spinel oxides
CdCr2O4 and HgCr2O4, where a robust half magnetization plateau has been
observed, is discussed.Comment: 4 pages, 4 figure

### A Quantum Perfect Lattice Action for Monopoles and Strings

A quantum perfect lattice action in four dimensions can be derived
analytically as a renormalized trajectory when we perform a block spin
transformation of monopole currents in a simple but non-trivial case of
quadratic monopole interactions. The spectrum of the lattice theory is
identical to that of the continuum theory. The perfect monopole action is
transformed exactly into a lattice action of a string model. A perfect operator
evaluating a static potential between electric charges is also derived
explicitly. If the monopole interactions are weak as in the case of infrared
SU(2) QCD, the string interactions become strong. The static potential and the
string tension is estimated analytically by the use of the strong coupling
expansion and the continuum rotational invariance is restored completely.Comment: 16 pages, 1 figure; to be published in Phys. Lett.

### Monopole action and condensation in SU(2) QCD

An effective monopole action for various extended monopoles is derived from
vacuum configurations after abelian projection in the maximally abelian gauge
in $SU(2)$ QCD. The action appears to be independent of the lattice volume.
Moreover it seems to depend only on the physical lattice spacing of the
renormalized lattice, not on $\beta$. Entropy dominance over energy of monopole
loops is seen on the renormalized lattice with the spacing $b>b_c\simeq
5.2\times10^{-3} \Lambda_L^{-1}$. This suggests that monopole condensation
always (for all $\beta$) occurs in the infinite-volume limit of lattice QCD.Comment: 15 Pages+7 figures, KANAZAWA 94-1

### Risks after Disasters: A Note on the Effects of Precautionary Saving on Equity Premiums

This paper studies the effects on equity premiums of grisks after disastersh, which are defined as a sharp rise in volatility of real per capita GDP growth rates immediately following disasters. This paper makes three contributions. First, we analytically demonstrate that if and only if the degree of relative prudence is higher than 2, risks after disasters decrease equity premiums. Second, we find that the differences between equity premiums with and without risks after disasters are quantitatively significant. Third, equity premiums are still higher in the case of disaster than without a disaster.

### Risks after disasters: a note on the effects of precautionary saving on equity premiums

This paper studies the effects on equity premiums of Âgrisks after disastersÂh, which are defined as a sharp rise in volatility of real per capita GDP growth rates immediately following disasters. This paper makes three contributions. First, we analytically demonstrate that if and only if the degree of relative prudence is higher than 2, risks after disasters decrease equity premiums. Second, we find that the differences between equity premiums with and without risks after disasters are quantitatively significant. Third, equity premiums are still higher in the case of disaster than without a disaster.

### A perfect monopole action for SU(2) QCD

We found a quantum perfect lattice action in the 4-dimensional monopole
current theory which is known as an effective theory in the infrared region of
QCD. The perfect monopole action is transformed exactly into a lattice action
of a string model. When the monopole interactions are weak as in the case of
infrared SU(2) QCD, the string interactions are strong. The static potential
and the string tension in this region can be estimated analytically by the use
of the strong coupling expansion.Comment: Lattice99:Confinement sessio

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