20,698 research outputs found
Critical Phenomena and Thermodynamic Geometry of RN-AdS Black Holes
The phase transition of Reissner-Nordstr\"om black holes in
-dimensional anti-de Sitter spacetime is studied in details using the
thermodynamic analogy between a RN-AdS black hole and a van der Waals liquid
gas system. We first investigate critical phenomena of the RN-AdS black hole.
The critical exponents of relevant thermodynamical quantities are evaluated. We
find identical exponents for a RN-AdS black hole and a Van der Waals liquid gas
system. This suggests a possible universality in the phase transitions of these
systems. We finally study the thermodynamic behavior using the equilibrium
thermodynamic state space geometry and find that the scalar curvature diverges
exactly at the van der Waals-like critical point where the heat capacity at
constant charge of the black hole diverges.Comment: 18 pages, 5 figure
The meson annihilation to leptons and inclusive light hadrons
The annihilation of the meson to leptons and inclusive light hadrons is
analyzed in the framework of nonrelativistic QCD (NRQCD) factorization. We find
that the decay mode, which escapes from the helicity suppression, contributes a
sizable fraction width. According to the analysis, the branching ratio due to
the contribution from the color-singlet component of the meson can be of
order (10^{-2}). We also estimate the contributions from the color-octet
components. With the velocity scaling rule of NRQCD, we find that the
color-octet contributions are sizable too, especially, in certain phase space
of the annihilation they are greater than (or comparative to) the color-singlet
component. A few observables relevant to the spectrum of charged lepton are
suggested, that may be used as measurements on the color-octet and
color-singlet components in the future experiments. A typical long
distance contribution in the annihilation is estimated too.Comment: 26 pages, 5 figures (6 eps-files), submitted to Phys. Rev.
A Comparison of the Use of Binary Decision Trees and Neural Networks in Top Quark Detection
The use of neural networks for signal vs.~background discrimination in
high-energy physics experiment has been investigated and has compared favorably
with the efficiency of traditional kinematic cuts. Recent work in top quark
identification produced a neural network that, for a given top quark mass,
yielded a higher signal to background ratio in Monte Carlo simulation than a
corresponding set of conventional cuts. In this article we discuss another
pattern-recognition algorithm, the binary decision tree. We have applied a
binary decision tree to top quark identification at the Tevatron and found it
to be comparable in performance to the neural network. Furthermore,
reservations about the "black box" nature of neural network discriminators do
not apply to binary decision trees; a binary decision tree may be reduced to a
set of kinematic cuts subject to conventional error analysis.Comment: 14pp. Plain TeX + mtexsis.tex (latter available through 'get
mtexsis.tex'.) Two postscript files avail. by emai
The Casimir force of Quantum Spring in the (D+1)-dimensional spacetime
The Casimir effect for a massless scalar field on the helix boundary
condition which is named as quantum spring is studied in our recent
paper\cite{Feng}. In this paper, the Casimir effect of the quantum spring is
investigated in -dimensional spacetime for the massless and massive
scalar fields by using the zeta function techniques. We obtain the exact
results of the Casimir energy and Casimir force for any , which indicate a
symmetry of the two space dimensions. The Casimir energy and Casimir
force have different expressions for odd and even dimensional space in the
massless case but in both cases the force is attractive. In the case of
odd-dimensional space, the Casimir energy density can be expressed by the
Bernoulli numbers, while in the even case it can be expressed by the
-function. And we also show that the Casimir force has a maximum value
which depends on the spacetime dimensions. In particular, for a massive scalar
field, we found that the Casimir force varies as the mass of the field changes.Comment: 9 pages, 5 figures, v2, massive case added, refs. adde
Newton-Hooke Limit of Beltrami-de Sitter Spacetime, Principles of Galilei-Hooke's Relativity and Postulate on Newton-Hooke Universal Time
Based on the Beltrami-de Sitter spacetime, we present the Newton-Hooke model
under the Newton-Hooke contraction of the spacetime with respect to the
transformation group, algebra and geometry. It is shown that in Newton-Hooke
space-time, there are inertial-type coordinate systems and inertial-type
observers, which move along straight lines with uniform velocity. And they are
invariant under the Newton-Hooke group. In order to determine uniquely the
Newton-Hooke limit, we propose the Galilei-Hooke's relativity principle as well
as the postulate on Newton-Hooke universal time. All results are readily
extended to the Newton-Hooke model as a contraction of Beltrami-anti-de Sitter
spacetime with negative cosmological constant.Comment: 25 pages, 3 figures; some misprints correcte
Gravity waves over topographical bottoms: Comparison with the experiment
In this paper, the propagation of water surface waves over one-dimensional
periodic and random bottoms is investigated by the transfer matrix method. For
the periodic bottoms, the band structure is calculated, and the results are
compared to the transmission results. When the bottoms are randomized, the
Anderson localization phenomenon is observed. The theory has been applied to an
existing experiment (Belzons, et al., J. Fluid Mech. {\bf 186}, 530 (1988)). In
general, the results are compared favorably with the experimental observation.Comment: 15 pages, 7 figure
Pseuduscalar Heavy Quarkonium Decays With Both Relativistic and QCD Radiative Corrections
We estimate the decay rates of ,
, and ,
, by taking into account both relativistic and
QCD radiative corrections. The decay amplitudes are derived in the
Bethe-Salpeter formalism. The Bethe-Salpeter equation with a QCD-inspired
interquark potential are used to calculate the wave functions and decay widths
for these states. We find that the relativistic correction to the
ratio is negative and tends to compensate the positive contribution from
the QCD radiative correction. Our estimate gives and ,
which are smaller than their nonrelativistic values. The hadronic widths
and are then indicated accordingly to the first order
QCD radiative correction, if . The decay widths for
states are also estimated. We show that when making the assmption
that the quarks are on their mass shells our expressions for the decay widths
will become identical with that in the NRQCD theory to the next to leading
order of and .Comment: 14 pages LaTex (2 figures included
The Application of Micro-Raman Spectroscopy to Analysis and Identification of Minerals in Thin Section
Micro-Raman spectroscopy is a useful analytical tool for studying minerals in thin section. The advantages of this technique as a structural probe for analysis of micron-size minerals are demonstrated with a study of polymorphism of SiO2 and MgSiO3. Three polymorphs of silica, -quartz, coesite, and glass, in a thin section of Coconino sandstone were identified in situ with a Raman microprobe. The Raman spectra of these phases were compared to that measured for stishovite obtained from the same rock. Spectra of protoenstatite, orthoenstatite, and clinoenstatite, three polymorphs of MgSiO3, are consistent with their similar pyroxene chain structures but different space groups. The characteristic Raman spectra in each instance could be used for finger-printing identification of the phases and their orientations
Gluonic and leptonic decays of heavy quarkonia and the determination of and
QCD running coupling constant and are
determined from heavy quarkonia and decays. The
decay rates of and for and
are estimated by taking into account both relativistic and QCD
radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter
formalism, and the decay rates are estimated by using the meson wavefunctions
which are obtained with a QCD-inspired inter-quark potential. For the
decay we find the relativistic correction to be very large
and to severely suppress the decay rate. Using the experimental values of ratio
R_g\equiv \frac {\Gamma (V\longrightarrow 3g)}% {\Gamma (V\longrightarrow
e^{+}e^{-})}\approx 10,~32 for respectively, and the
calculated widths , we find and
. These values for the QCD running coupling
constant are substantially enhanced, as compared with the ones obtained without
relativistic corrections, and are consistent with the QCD scale parameter
. We also find that these
results are mainly due to kinematic corrections and not sensitive to the
dynamical models.Comment: 15 pages in Late
Mechanisms for electron transport in atomic-scale one-dimensional wires: soliton and polaron effects
We study one-electron tunneling through atomic-scale one-dimensional wires in
the presence of coherent electron-phonon (e-ph) coupling. We use a full quantum
model for the e-ph interaction within the wire with open boundary conditions.
We illustrate the mechanisms of transport in the context of molecular wires
subject to boundary conditions imposing the presence of a soliton defect in the
molecule. Competition between polarons and solitons in the coherent transport
is examined. The transport mechanisms proposed are generally applicable to
other one-dimensional nanoscale systems with strong e-ph coupling.Comment: 7 pages, 4 figures, accepted for publication in Europhys. Let
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