27,136 research outputs found
Metastability of R-Charged Black Holes
The global stability of R-charged AdS black holes in a grand canonical
ensemble is examined by eliminating the constraints from the action, but
without solving the equations of motion, thereby constructing the reduced
action of the system. The metastability of the system is found to set in at a
critical value of the chemical potential which is conjugate to the R-charge.
The relation among the small black hole, large black hole and the instability
is discussed. The result is consistent with the metastability found in the
AdS/CFT-conjectured dual field theory. The "renormalized" temperature of AdS
black holes, which has been rather ad hoc, is suggested to be the boundary
temperature in the sense of AdS/CFT correspondence. As a byproduct of the
analysis, we find a more general solution of the theory and its properties are
briefly discussed.Comment: 36 pages, 7 figures, v2 is the published version. the exposition is
made slightly shorter and hopefully cleare
Hydrogen-Bonded Liquids: Effects of Correlations of Orientational Degrees of Freedom
We improve a lattice model of water introduced by Sastry, Debenedetti,
Sciortino, and Stanley to give insight on experimental thermodynamic anomalies
in supercooled phase, taking into account the correlations between
intra-molecular orientational degrees of freedom. The original Sastry et al.
model including energetic, entropic and volumic effect of the
orientation-dependent hydrogen bonds (HBs), captures qualitatively the
experimental water behavior, but it ignores the geometrical correlation between
HBs. Our mean-field calculation shows that adding these correlations gives a
more water-like phase diagram than previously shown, with the appearance of a
solid phase and first-order liquid-solid and gas-solid phase transitions.
Further investigation is necessary to be able to use this model to characterize
the thermodynamic properties of the supercooled region.Comment: 7 pages latex, 3 figures EP
Localization Properties of Electronic States in Polaron Model of poly(dG)-poly(dC) and poly(dA)-poly(dT) DNA polymers
We numerically investigate localization properties of electronic states in a
static model of poly(dG)-poly(dC) and poly(dA)-poly(dT) DNA polymers with
realistic parameters obtained by quantum-chemical calculation. The randomness
in the on-site energies caused by the electron-phonon coupling are completely
correlated to the off-diagonal parts. In the single electron model, the effect
of the hydrogen-bond stretchings, the twist angles between the base pairs and
the finite system size effects on the energy dependence of the localization
length and on the Lyapunov exponent are given. The localization length is
reduced by the influence of the fluctuations in the hydrogen bond stretchings.
It is also shown that the helical twist angle affects the localization length
in the poly(dG)-poly(dC) DNA polymer more strongly than in the
poly(dA)-poly(dT) one. Furthermore, we show resonance structures in the energy
dependence of the localization length when the system size is relatively small.Comment: 6 pages, 6 figure
Multi-cluster dynamics in and analogy to clustering in
We investigate structure of and discuss the difference
and similarity between the structures of and by answering the questions if the linear-chain and gaslike cluster states,
which are proposed to appear in , survives, or new structure
states appear or not. We introduce a microscopic cluster model called,
Hyper-Tohsaki-Horiuchi-Schuck-R\"opke (H-THSR) wave function, which is an
extended version of the THSR wave function so as to describe
hypernuclei. We obtained two bound states and two resonance (quasi-bound)
states for in , corresponding to the four
states in . However, the inversion of level ordering
between the spectra of and , i.e. that the
and states in correspond to the
and states in , respectively, is shown to occur. The
additional particle reduces sizes of the and states
in very much, but the shrinkage of the state is
only a half of the other states. In conclusion, the Hoyle state becomes quite a
compact object with configuration in
and is no more gaslike state composed of the
clusters. Instead, the state in , coming from the
state, appears as a gaslike state composed of
configuration, i.e. the Hoyle analog
state. A linear-chain state in a hypernucleus is for the first time
predicted to exist as the state in with more
shrunk arrangement of the clusters along -axis than the
linear-chain configuration realized in the state.Comment: 9 pages, 6 figures, figures rearranged, accepted for publication in
PL
Influence of the definition of dissipative events on their statistics
A convenient and widely used way to study the turbulent plasma in the solar
corona is to do statistics of properties of events (or structures), associated
with flares, that can be found in observations or in numerical simulations.
Numerous papers have followed such a methodology, using different definitions
of an event, but the reasons behind the choice of a particular definition (and
not another one) is very rarely discussed. We give here a comprehensive set of
possible event definitions starting from a one-dimensional data set such as a
time-series of energy dissipation. Each definition is then applied to a
time-series of energy dissipation issued from simulations of a shell-model of
magnetohydrodynamic turbulence as defined in Giuliani and Carbone (1998), or
from a new model of coupled shell-models designed to represent a magnetic loop
in the solar corona. We obtain distributions of the peak dissipation power,
total energy, duration and waiting-time associated to each definition. These
distributions are then investigated and compared, and the influence of the
definition of an event on statistics is discussed. In particular, power-law
distributions are more likely to appear when using a threshold. The sensitivity
of the distributions to the definition of an event seems also to be weaker for
events found in a highly intermittent time series. Some implications on
statistical results obtained from observations are discussed.Comment: 8 pages, 13 figures. Submitted to Astronomy&Astrophysic
A light Higgs scenario based on the TeV-scale supersymmetric strong dynamics
We consider a model based on the supersymmetric QCD theory with N_c=2 and
N_f=3. The theory is strongly coupled at the infrared scale \Lambda_H. Its low
energy effective theory below \Lambda_H is described by the supersymmetric
standard model with the Higgs sector that contains four iso-spin doublets, two
neutral iso-spin singlets and two charged iso-spin singlets. If \Lambda_H is at
the multi-TeV to 10 TeV, coupling constants for the F-terms of these composite
fields are relatively large at the electroweak scale. Nevertheless, the SM-like
Higgs boson is predicted to be as light as 125 GeV because these F-terms
contribute to the mass of the SM-like Higgs boson not at the tree level but at
the one-loop level. A large non-decoupling effect due to these F-terms appears
in the one-loop correction to the triple Higgs boson coupling, which amounts to
a few tens percent. Such a non-decoupling property in the Higgs potential
realizes the strong first order phase transition, which is required for a
successful scenario of electroweak baryogenesis
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