160,770 research outputs found
Monomial Testing and Applications
In this paper, we devise two algorithms for the problem of testing
-monomials of degree in any multivariate polynomial represented by a
circuit, regardless of the primality of . One is an time
randomized algorithm. The other is an time deterministic
algorithm for the same -monomial testing problem but requiring the
polynomials to be represented by tree-like circuits. Several applications of
-monomial testing are also given, including a deterministic
upper bound for the -set -packing problem.Comment: 17 pages, 4 figures, submitted FAW-AAIM 2013. arXiv admin note:
substantial text overlap with arXiv:1302.5898; and text overlap with
arXiv:1007.2675, arXiv:1007.2678, arXiv:1007.2673 by other author
Vanishing Viscosity Approach to the Compressible Euler Equations for Transonic Nozzle and Spherically Symmetric Flows
We are concerned with globally defined entropy solutions to the Euler
equations for compressible fluid flows in transonic nozzles with general
cross-sectional areas. Such nozzles include the de Laval nozzles and other more
general nozzles whose cross-sectional area functions are allowed at the nozzle
ends to be either zero (closed ends) or infinity (unbounded ends). To achieve
this, in this paper, we develop a vanishing viscosity method to construct
globally defined approximate solutions and then establish essential uniform
estimates in weighted norms for the whole range of physical adiabatic
exponents , so that the viscosity approximate solutions
satisfy the general compensated compactness framework. The viscosity
method is designed to incorporate artificial viscosity terms with the natural
Dirichlet boundary conditions to ensure the uniform estimates. Then such
estimates lead to both the convergence of the approximate solutions and the
existence theory of globally defined finite-energy entropy solutions to the
Euler equations for transonic flows that may have different end-states in the
class of nozzles with general cross-sectional areas for all . The approach and techniques developed here apply to other problems
with similar difficulties. In particular, we successfully apply them to
construct globally defined spherically symmetric entropy solutions to the Euler
equations for all .Comment: 32 page
Further analysis of field effects on liquids and solidification
Numerical calculations of the magnitude of external field effects on liquids are presented to describe how external fields can influence the substructure of the field. Quantitative estimates of magnetic and gravitational effects are reported on melts of metals and semiconductors. The results are condensed in tables which contain the input data for calculation of the field effects on diffusion coefficient, solidification rate and for calculation of field forces on individual molecules in the melt
Gravitational Laser Back-Scattering
A possible way of producing gravitons in the laboratory is investigated. We
evaluate the cross section electron + photon electron + graviton
in the framework of linearized gravitation, and analyse this reaction
considering the photon coming either from a laser beam or from a Compton
back-scattering process.Comment: 11 pages, 2 figures (available upon request), RevTeX, IFT-P.03/9
Early Time Dynamics of Gluon Fields in High Energy Nuclear Collisions
Nuclei colliding at very high energy create a strong, quasi-classical gluon
field during the initial phase of their interaction. We present an analytic
calculation of the initial space-time evolution of this field in the limit of
very high energies using a formal recursive solution of the Yang-Mills
equations. We provide analytic expressions for the initial chromo-electric and
chromo-magnetic fields and for their energy-momentum tensor. In particular, we
discuss event-averaged results for energy density and energy flow as well as
for longitudinal and transverse pressure of this system. For example, we find
that the ratio of longitudinal to transverse pressure very early in the system
behaves as where
is the longitudinal proper time, is related to the saturation scales
of the two nuclei, and with a scale to
be defined later. Our results are generally applicable if .
As already discussed in a previous paper, the transverse energy flow of
the gluon field exhibits hydrodynamic-like contributions that follow transverse
gradients of the energy density . In addition, a
rapidity-odd energy flow also emerges from the non-abelian analog of Gauss' Law
and generates non-vanishing angular momentum of the field. We will discuss the
space-time picture that emerges from our analysis and its implications for
observables in heavy ion collisions.Comment: 26 pages, 9 figure
EffiTest: Efficient Delay Test and Statistical Prediction for Configuring Post-silicon Tunable Buffers
At nanometer manufacturing technology nodes, process variations significantly
affect circuit performance. To combat them, post- silicon clock tuning buffers
can be deployed to balance timing bud- gets of critical paths for each
individual chip after manufacturing. The challenge of this method is that path
delays should be mea- sured for each chip to configure the tuning buffers
properly. Current methods for this delay measurement rely on path-wise
frequency stepping. This strategy, however, requires too much time from ex-
pensive testers. In this paper, we propose an efficient delay test framework
(EffiTest) to solve the post-silicon testing problem by aligning path delays
using the already-existing tuning buffers in the circuit. In addition, we only
test representative paths and the delays of other paths are estimated by
statistical delay prediction. Exper- imental results demonstrate that the
proposed method can reduce the number of frequency stepping iterations by more
than 94% with only a slight yield loss.Comment: ACM/IEEE Design Automation Conference (DAC), June 201
Ab initio study of electron transport in dry poly(G)-poly(C) A-DNA strands
The bias-dependent transport properties of short poly(G)-poly(C) A-DNA
strands attached to Au electrodes are investigated with first principles
electronic transport methods. By using the non- equilibrium Green's function
approach combined with self-interaction corrected density functional theory, we
calculate the fully self-consistent coherent I-V curve of various double-strand
polymeric DNA fragments. We show that electronic wave-function localization,
induced either by the native electrical dipole and/or by the electrostatic
disorder originating from the first few water solvation layers, drastically
suppresses the magnitude of the elastic conductance of A-DNA oligonucleotides.
We then argue that electron transport through DNA is the result of
sequence-specific short-range tunneling across a few bases combined with
general diffusive/inelastic processes.Comment: 15 pages, 13 figures, 1 tabl
Are Giant Planets Forming Around HR 4796A?
We have obtained FUSE and HST STIS spectra of HR 4796A, a nearby 8 Myr old
main sequence star that possesses a dusty circumstellar disk whose inclination
has been constrained from high resolution near-infrared observations to be ~17
deg from edge-on. We searched for circumstellar absorption in the ground states
of C II at 1036.3 A, O I at 1039.2 A, Zn II at 2026.1 A, Lyman series H2, and
CO (A-X) and failed to detect any of these species. We place upper limits on
the column densities and infer upper limits on the gas masses assuming that the
gas is in hydrostatic equilibrium, is well-mixed, and has a temperature, Tgas ~
65 K. Our measurements suggest that this system possesses very little molecular
gas. Therefore, we infer an upper limit for the gas:dust ratio (<4.0) assuming
that the gas is atomic. We measure less gas in this system than is required to
form the envelope of Jupiter.Comment: 10 pages, 3 figures (including 1 color figure), accepted for
publication in Ap
Electronic Structure of New AFFeAs Prototype of Iron Arsenide Superconductors
This work is provoked by recent discovery of new class prototype systems
AFFeAs (A=Sr,Ca) of novel layered ironpnictide High-Tc superconductors
(Tc=36K). Here we report ab initio LDA results for electronic structure of the
AFFeAs systems. We provide detailed comparison between electronic properties of
both new systems and reference LaOFeAs (La111) compound. In the vicinity of the
Fermi level all three systems have essentially the same band dispersions.
However for iron fluoride systems F(2p) states were found to be separated in
energy from As(4p) ones in contrast to La111, where O(2p) states strongly
overlaps with As(4p). Thus it should be more plausible to include only Fe(3d)
and As(4p) orbitals into a realistic noninteracting model than for La111.
Moreover Sr substitution with smaller ionic radius Ca in AFFeAs materials leads
to a lattice contruction and stronger Fe(3d)-As(4p) hybridization resulting in
smaller value of the density of states at the Fermi level in the case of Ca
compound. So to some extend Ca system reminds RE111 with later Rare Earths.
However Fermi surface of new fluorides is found to be nearly perfect
two-dimensional. Also we do not expect strong dependence of superconducting
properties with respect to different types of A substitutes.Comment: 5 pages, 4 figure
Characterizing Entanglement via Uncertainty Relations
We derive a family of necessary separability criteria for finite-dimensional
systems based on inequalities for variances of observables. We show that every
pure bipartite entangled state violates some of these inequalities.
Furthermore, a family of bound entangled states and true multipartite entangled
states can be detected. The inequalities also allow to distinguish between
different classes of true tripartite entanglement for qubits. We formulate an
equivalent criterion in terms of covariance matrices. This allows us to apply
criteria known from the regime of continuous variables to finite-dimensional
systems.Comment: 4 pages, no figures. v2: Some discussion added, main results
unchange
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