109,735 research outputs found
Ab initio study of the thermodynamic properties of rare-earthmagnesium intermetallics MgRE (RE=Y, Dy, Pr, Tb)
We have performed an ab initio study of the thermodynamical properties of
rare-earth-magnesium intermetallic compounds MgRE (RE=Y, Dy, Pr, Tb) with
CsCl-type B2-type structures. The calculations have been carried out the
density functional theory and density functional perturbation theory in
combination with the quasiharmonic approximation. The phonon-dispersion curves
and phonon total and partial density of states have been investigated. Our
results show that the contribution of RE atoms is dominant in phonon frequency,
and this character agrees with the previous discussion by using atomistic
simulations. The temperature dependence of various quantities such as the
thermal expansions, bulk modulus, and the heat capacity are obtained. The
electronic contributions to the specific heat are discussed, and found to be
important for the calculated MgRE intermetallics.Comment: 12 pages, 6 figure
Lattice Statistics in Three Dimensions: Exact Solution of Layered Dimer and Layered Domain Wall Models
Exact analyses are given for two three-dimensional lattice systems: A system
of close-packed dimers placed in layers of honeycomb lattices and a layered
triangular-lattice interacting domain wall model, both with nontrivial
interlayer interactions. We show that both models are equivalent to a 5-vertex
model on the square lattice with interlayer vertex-vertex interactions. Using
the method of Bethe ansatz, a closed-form expression for the free energy is
obtained and analyzed. We deduce the exact phase diagram and determine the
nature of the phase transitions as a function of the strength of the interlayer
interaction.Comment: 22 pages in Revtex, 6 PS files, submitted to PR
Hawking Radiation of an Arbitrarily Accelerating Kinnersley Black Hole: Spin-Acceleration Coupling Effect
The Hawking radiation of Weyl neutrinos in an arbitrarily accelerating
Kinnersley black hole is investigated by using a method of the generalized
tortoise coordinate transformation. Both the location and temperature of the
event horizon depend on the time and on the angles. They coincide with previous
results, but the thermal radiation spectrum of massless spinor particles
displays a kind of spin-acceleration coupling effect.Comment: 8 pages, no figure, revtex 4.0, revisted version with typesetting
errors and misprint correcte
Hawking radiation from the Schwarzschild black hole with a global monopole via gravitational anomaly
Hawking flux from the Schwarzschild black hole with a global monopole is
obtained by using Robinson and Wilczek's method. Adopting a dimension reduction
technique, the effective quantum field in the (3+1)--dimensional global
monopole background can be described by an infinite collection of the
(1+1)--dimensional massless fields if neglecting the ingoing modes near the
horizon, where the gravitational anomaly can be cancelled by the
(1+1)--dimensional black body radiation at the Hawking temperature.Comment: 4 pages, no figure, 3nd revsion with one reference adde
Two-photon absorption and broadband optical limiting with bis-donor stilbenes
Large two-photon absorptivities are reported for symmetrical bis-donor stilbene derivatives with dialkylamino or diphenylamino groups. These molecules exhibit strong optical limiting of nanosecond pulses over a broad spectral range in the visible. Relative to bis(di-n-butylamino)stilbene, bis(diphenylamino)stilbene exhibits a 90-nm red shift of its optical limiting band but only a minimal shift of ~13 nm of its lowest one-photon electronic absorption band. Mixtures of these compounds offer an unprecedented combination of broad optical limiting bandwidth and high linear transparency
Robust strongly-modulated transmission of a -shaped structure with local Rashba interaction
We propose a scheme of spin transistor using a -shaped structure with
local Rashba interaction. A wide antiresonance energy gap appears due to the
interplay of two types of interference, the Fano-Rashba interference and the
structure interference. A large current from the gap area can be obtained via
changing the Rashba strength and/or the length of the sidearm by using gate
voltage. The robustness of the antiresonance gap against strong disorder is
demonstrated and shows the feasibility of this structure for the real
application.Comment: 4 pages, 3 figures, To be published in PR
Two Higgs Bi-doublet Left-Right Model With Spontaneous P and CP Violation
A left-right symmetric model with two Higgs bi-doublet is shown to be a
consistent model for both spontaneous P and CP violation. The flavor changing
neutral currents can be suppressed by the mechanism of approximate global U(1)
family symmetry. We calculate the constraints from neural meson mass
difference and demonstrate that a right-handed gauge boson
contribution in box-diagrams with mass well below 1 TeV is allowed due to a
cancellation caused by a light charged Higgs boson with a mass range GeV. The contribution to can be suppressed from
appropriate choice of additional CP phases appearing in the right-handed
Cabbibo-Kobayashi-Maskawa matrix. The model is also found to be fully
consistent with mass difference , and the mixing-induced CP
violation quantity , which is usually difficult for the
model with only one Higgs bi-doublet. The new physics beyond the standard model
can be directly searched at the colliders LHC and ILC.Comment: 25 pages, 6 figures, typos corrected, 1 figure added, published
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