922 research outputs found
The PMS project: Poor Man's Supercomputer
We briefly describe the Poor Man's Supercomputer (PMS) project carried out at
Eotvos University, Budapest. The goal was to develop a cost effective,
scalable, fast parallel computer to perform numerical calculations of physical
problems that can be implemented on a lattice with nearest neighbour
interactions. To this end we developed the PMS architecture using PC components
and designed a special, low cost communication hardware and the driver software
for Linux OS. Our first implementation of PMS includes 32 nodes (PMS1). The
performance of PMS1 was tested by Lattice Gauge Theory simulations. Using SU(3)
pure gauge theory or bosonic MSSM on PMS1 we obtained 3Mflop
price-to-sustained performance for double and single precision operations,
respectively. The design of the special hardware and the communication driver
are freely available upon request for non-profit organizations.Comment: Latex, 13 pages, 6 figures included, minor additions, typos correcte
-dimensions Dirac fermions BEC-BCS cross-over thermodynamics
An effective Proca Lagrangian action is used to address the vector
condensation Lorentz violation effects on the equation of state of the strongly
interacting fermions system. The interior quantum fluctuation effects are
incorporated as an external field approximation indirectly through a fictive
generalized Thomson Problem counterterm background. The general analytical
formulas for the -dimensions thermodynamics are given near the unitary limit
region. In the non-relativistic limit for , the universal dimensionless
coefficient and energy gap are
reasonably consistent with the existed theoretical and experimental results. In
the unitary limit for and T=0, the universal coefficient can even
approach the extreme occasion corresponding to the infinite effective
fermion mass which can be mapped to the strongly coupled
two-dimensions electrons and is quite similar to the three-dimensions
Bose-Einstein Condensation of ideal boson gas. Instead, for , the
universal coefficient is negative, implying the non-existence of phase
transition from superfluidity to normal state. The solutions manifest the
quantum Ising universal class characteristic of the strongly coupled unitary
fermions gas.Comment: Improved versio
Multi-layered Ruthenium-modified Bond Coats for Thermal Barrier Coatings
Diffusional approaches for fabrication of multi-layered Ru-modified bond coats for thermal
barrier coatings have been developed via low activity chemical vapor deposition and high activity
pack aluminization. Both processes yield bond coats comprising two distinct B2 layers, based on
NiAl and RuAl, however, the position of these layers relative to the bond coat surface is reversed
when switching processes. The structural evolution of each coating at various stages of the
fabrication process has been and subsequent cyclic oxidation is presented, and the relevant
interdiffusion and phase equilibria issues in are discussed. Evaluation of the oxidation behavior of
these Ru-modified bond coat structures reveals that each B2 interlayer arrangement leads to the
formation of α-Al 2 O 3 TGO at 1100°C, but the durability of the TGO is somewhat different and in
need of further improvement in both cases
Renormalization group and isochronous oscillations
We show how the condition of isochronicity can be studied for two dimensional
systems in the renormalization group (RG) context. We find a necessary
condition for the isochronicity of the Cherkas and another class of cubic
systems. Our conditions are satisfied by all the cases studied recently by
Bardet et al \cite{bard} and Ghose Choudhury and Guh
F-theory and the Witten Index
We connect the fermionic fields, localized on the intersection curve
of two D7-branes with zero background flux, to a N=2 supersymmetric quantum
mechanics algebra, within the theoretical framework of F-theory
F-theory Yukawa Couplings and Supersymmetric Quantum Mechanics
The localized fermions on the intersection curve of D7-branes, are
connected to a N=2 supersymmetric quantum mechanics algebra. Due to this
algebra the fields obey a global U(1) symmetry. This symmetry restricts the
proton decay operators and the neutrino mass terms. Particularly, we find that
several proton decay operators are forbidden and the Majorana mass term is the
only one allowed in the theory. A special SUSY QM algebra is studied at the end
of the paper. In addition we study the impact of a non-trivial holomorphic
metric perturbation on the localized solutions along each matter curve.
Moreover, we study the connection of the localized solutions to an N=2
supersymmetric quantum mechanics algebra when background fluxes are turned on.Comment: References added, New Material Added, Published versio
Hydrodynamics of domain growth in nematic liquid crystals
We study the growth of aligned domains in nematic liquid crystals. Results
are obtained solving the Beris-Edwards equations of motion using the lattice
Boltzmann approach. Spatial anisotropy in the domain growth is shown to be a
consequence of the flow induced by the changing order parameter field
(backflow). The generalization of the results to the growth of a cylindrical
domain, which involves the dynamics of a defect ring, is discussed.Comment: 12 revtex-style pages, including 12 figures; small changes before
publicatio
Comparison of Radiation Damage in Lead Tungstate Crystals under Pion and Gamma Irradiation
Studies of the radiation hardness of lead tungstate crystals produced by the
Bogoroditsk Techno-Chemical Plant in Russia and the Shanghai Institute of
Ceramics in China have been carried out at IHEP, Protvino. The crystals were
irradiated by a 40-GeV pion beam. After full recovery, the same crystals were
irradiated using a -ray source. The dose rate profiles along
the crystal length were observed to be quite similar. We compare the effects of
the two types of radiation on the crystals light output.Comment: 10 pages, 8 figures, Latex 2e, 28.04.04 - minor grammatical change
LED Monitoring System for the BTeV Lead Tungstate Crystal Calorimeter Prototype
We report on the performance of a monitoring system for a prototype
calorimeter for the BTeV experiment that uses Lead Tungstate crystals coupled
with photomultiplier tubes. The tests were carried out at the 70 GeV
accelerator complex at Protvino, Russia.Comment: 12 pages, 8 figures, LaTeX2e, revised versio
Loop Corrections to Cosmological Perturbations in Multi-field Inflationary Models
We investigate one-loop quantum corrections to the power spectrum of
adiabatic perturbation from entropy modes/adiabatic mode cross-interactions in
multiple DBI inflationary models. We find that due to the non-canonical kinetic
term in DBI models, the loop corrections are enhanced by slow-varying parameter
and small sound speed . Thus, in general the loop-corrections
in multi-DBI models can be large. Moreover, we find that the loop-corrections
from adiabatic/entropy cross-interaction vertices are IR finite.Comment: 21 pages, 7 figures; v2, typos corrected, ref added; v3 typos
corrected, version for publishing in jca
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