1,233,470 research outputs found
High Dielectric Permittivity in AFeBO Nonferroelectric Perovskite Ceramics (A - Ba, Sr, Ca; B - Nb, Ta, Sb)
AFeBO(A- Ba, Sr, Ca; B-Nb, Ta, Sb) ceramics were
synthesized and temperature dependencies of the dielectric permittivity were
measured at different frequencies. The experimental data obtained show very
high values of the dielectric permittivity in a wide temperature interval that
is inherent to so-called high-k materials. The analyses of these data establish
a Maxwell-Wagner mechanism as a main source for the phenomenon observed.Comment: 6 pages, 7 figure
Comment on "Equivalence of the variational matrix product method and the density matrix renormalization group applied to spin chains"
Dukelsky, Mart\'in-Delgado, Nishino and Sierra (Europhys. Lett., 43, 457
(1998) - hereafter referred to as DMNS) investigated the matrix product method
(MPM), comparing it with the infinite-size density matrix renormalization group
(DMRG). For equivalent basis size, the MPM produces an improved variational
energy over that produced by DMRG and, unlike DMRG, produces a
translationally-invariant wavefunction. The DMRG results presented were
significantly worse than the MPM, caused by a shallow bound state appearing at
the join of the two DMRG blocks. They also suggested that the DMRG results can
be improved by using an alternate superblock construction for
the last few steps of the calculation. In this comment, we show that the DMRG
results presented by DMNS are in error and the artificial bound state produced
by the standard superblock configuration is very small even for states
kept. In addition, we calculate explicitly the energy and wavefunction for the
superblock structure and verify that the energy coincides
with that of the MPM, as conjectured by S. Ostlund and S. Rommer (Phys. Rev.
Lett., 75, 3537 (1995)).Comment: 2 pages, 1 eps figure included. eps.cls include
Z_p scalar dark matter from multi-Higgs-doublet models
In many models, stability of dark matter particles is protected by a
conserved Z_2 quantum number. However dark matter can be stabilized by other
discrete symmetry groups, and examples of such models with custom-tailored
field content have been proposed. Here we show that electroweak symmetry
breaking models with N Higgs doublets can readily accommodate scalar dark
matter candidates stabilized by groups Z_p with any , leading to
a variety of kinds of microscopic dynamics in the dark sector. We give examples
in which semi-annihilation or multiple semi-annihilation processes are allowed
or forbidden, which can be especially interesting in the case of asymmetric
dark matter.Comment: 10 page
Ground-state properties of fermionic mixtures with mass imbalance in optical lattices
Ground-state properties of fermionic mixtures confined in a one-dimensional
optical lattice are studied numerically within the spinless Falicov-Kimball
model with a harmonic trap. A number of remarkable results are found. (i) At
low particle filling the system exhibits the phase separation with heavy atoms
in the center of the trap and light atoms in the surrounding regions. (ii)
Mott-insulating phases always coexist with metallic phases. (iii)
Atomic-density waves are observed in the insulating regions for all particle
fillings near half-filled lattice case. (iv) The variance of the local density
exhibits the universal behavior (independent of the particle filling, the
Coulomb interaction and the strength of a confining potential) over the whole
region of the local density values.Comment: 10 pages, 5 figure
Jet Physics in Heavy Ion Collisions with Compact Muon Solenoid detector at the LHC
The status of CMS jet simulations and physics analysis in heavy ion
collisions is presented. Jet reconstruction and high transverse momentum
particle tracking in the high multiplicity environment of heavy ion collisions
at the LHC using the CMS calorimetry and tracking system are described. The
Monte Carlo tools used to simulate jet quenching are discussed.Comment: Talk given at 5th International Conference on Physics and
Astrophysics of Quark Gluon Plasma, Salt Lake City, Kolkata, India, February
8-12, 2005; 4 pages including 4 figures as EPS-files; prepared using LaTeX
package for Journal of Physics
Simulation of jet quenching at RHIC and LHC
The model to simulate jet quenching effect in ultrarelativistic heavy ion
collisions is presented. The model is the fast Monte-Carlo tool implemented to
modify a standard PYTHIA jet event. The model has been generalized to the case
of the "full" heavy ion event (the superposition of soft, hydro-type state and
hard multi-jets) using a simple and fast simulation procedure for soft particle
production. The model is capable of reproducing main features of the jet
quenching pattern at RHIC and is applyed to analyze novel jet quenching
features at LHC.Comment: Talk given at 19th International Conference on Ultra-Relativistic
Nucleus-Nucleus Collisions "Quark Matter 2006" (Shanghai, China, November
14-20, 2006); 4 pages including 2 figures as EPS-files; prepared using LaTeX
package for Journal of Physics
Fundamental aspects of the feeding of the amphipod Gammarus (R.) balcanicus (Crustacea, Amphipoda). [Translation from: Nauchn.Dokl.vyssh.Shkoly (Biol.Nauk) 1970(7) 12-16, 1970]
The amphipods are major food items for many commercial fishes, and they are used as protein food for agricultural animals. In the present paper are presented the results of four-year observations on the feeding of Gammarus balcanicus in nature and in an aquarium. Among the studied aspects were the dependence of daily food ration on sex and physiological state (with and without eggs) and feeding on different kinds of plant food. The study concludes that Gammarus balcanicus willingly feed on soft half-decayed plant residues; into their ration also enters food of animal origin. In contrast to other amphipods, G. balcanicus eats representatives of its own species very rarely, and only dead or immobile ones
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