422 research outputs found
Techniques for improving reliability of computers
Modular design techniques improve methods of error detection, diagnosis, and recovery. Theoretical computer (MARCS (Modular Architecture for Reliable Computer Systems)) study deals with postulated and modeled technology indigenous to 1975-1980. Study developments are discussed
Exact Solution of the One-Dimensional Non-Abelian Coulomb Gas at Large N
The problem of computing the thermodynamic properties of a one-dimensional
gas of particles which transform in the adjoint representation of the gauge
group and interact through non-Abelian electric fields is formulated and solved
in the large limit. The explicit solution exhibits a first order
confinement-deconfinement phase transition with computable properties and
describes two dimensional adjoint QCD in the limit where matter field masses
are large.Comment: 8 pages, late
Universal Cellular Automata and Class 4
Wolfram has provided a qualitative classification of cellular automata(CA)
rules according to which, there exits a class of CA rules (called Class 4)
which exhibit complex pattern formation and long-lived dynamical activity (long
transients). These properties of Class 4 CA's has led to the conjecture that
Class 4 rules are Universal Turing machines i.e. they are bases for
computational universality. We describe an embedding of a ``small'' universal
Turing machine due to Minsky, into a cellular automaton rule-table. This
produces a collection of cellular automata, all of which are
computationally universal. However, we observe that these rules are distributed
amongst the various Wolfram classes. More precisely, we show that the
identification of the Wolfram class depends crucially on the set of initial
conditions used to simulate the given CA. This work, among others, indicates
that a description of complex systems and information dynamics may need a new
framework for non-equilibrium statistical mechanics.Comment: Latex, 10 pages, 5 figures uuencode
Search for Decay in LSND
We observe a net beam-excess of (stat) (syst) events,
above 160 MeV, resulting from the charged-current reaction of
and/or on C and H in the LSND detector. No beam related muon
background is expected in this energy regime. Within an analysis framework of
, we set a direct upper limit for this
branching ratio of at 90% confidence level.Comment: 4 pages, 4 figure
GT-2002-30326 FORWARD SWEPT ROTOR STUDIES IN MULTISTAGE FANS WITH INLET DISTORTION
ABSTRACT Previous experimental and analytical studies conducted to compare the performance of transonic swept rotors in single stage fans have demonstrated the potential of significant improvements in both efficiency and stall margin with forward swept blading. This paper extends the assessment of the payoff derived from forward sweep with respect to aerodynamic performance and stability to multistage configurations. The experimental investigation compares, on a back-to-back test basis, two builds of an advanced good efficiency, high pressure ratio, two-stage fan configuration tested alternately with a radial and a forward swept stage 1 blade. In the two-stage evaluations, the testing was extended to include the effect on inlet flow distortion. While the common second stage among the two builds prevented the overall fan from showing clean inlet performance and stability benefits with the forward swept rotor 1, this configuration did demonstrate superior front stage efficiency and tolerance to inlet distortion. Having obtained an already low distortion sensitivity with the radial rotor 1 configuration relative to current production military fan standards, the sensitivity to inlet distortion was halved with the forward swept rotor 1 configuration. In the case of the 180-degree one-per-rev distortion pattern, the two-stage configuration was evaluated both with and without inlet guide vanes (IGVs). The presence of the inlet guide vanes had a profound impact in lowering the two stage fan's sensitivity with inlet distortion
Phases of one dimensional large N gauge theory in a 1/D expansion
We consider large N Yang Mills theory with D adjoint scalar fields in d
dimensions for d=0 or 1. We show the existence of a non-trivial saddle point of
the functional integral at large D which is characterized by a mass gap for the
adjoint scalars. We integrate out the adjoint scalars in a 1/D expansion around
the saddle point. In case of one dimension which is regarded as a circle, this
procedure leads to an effective action for the Wilson line. We find an analogue
of the confinement/deconfinement transition which consists of a second order
phase transition from a uniform to a non-uniform eigenvalue distribution of the
Wilson line, closely followed by a Gross-Witten-Wadia transition where a gap
develops in the eigenvalue distribution. The phase transition can be regarded
as a continuation of a Gregory-Laflamme transition. Our methods involve large
values of the dimensionless 'tHooft coupling. The analysis in this paper is
quantitatively supported by earlier numerical work for D=9.Comment: 27 pages + 21 pages of Appendix; 8 figures, v2:some comments are
added in sec.4.3, minor corrections, one reference added, v3: minor
corrections, one reference added, version to be published in JHE
Measurements of Charged Current Reactions of on
Charged Current reactions of on have been studied using a
decay-at-rest beam at the Los Alamos Neutron Science Center.
The cross section for the exclusive reaction
was measured to be cm. The observed
energy dependence of the cross section and angular distribution of the outgoing
electron agree well with theoretical expectations. Measurements are also
presented for inclusive transitions to excited states,
and compared with theoretical expectations. The
measured cross section, cm, is somewhat
lower than previous measurements and than a continuum random phase
approximation calculation. It is in better agreement with a recent shell model
calculation.Comment: 34 pages, 18 figures, accepted to PRC, replaced with the accepted on
Constraining conformal field theories with a slightly broken higher spin symmetry
We consider three dimensional conformal field theories that have a higher
spin symmetry that is slightly broken. The theories have a large N limit, in
the sense that the operators separate into single trace and multitrace and obey
the usual large N factorization properties. We assume that the spectrum of
single trace operators is similar to the one that one gets in the Vasiliev
theories. Namely, the only single trace operators are the higher spin currents
plus an additional scalar. The anomalous dimensions of the higher spin currents
are of order 1/N. Using the slightly broken higher spin symmetry we constrain
the three point functions of the theories to leading order in N. We show that
there are two families of solutions. One family can be realized as a theory of
N fermions with an O(N) Chern-Simons gauge field, the other as a N bosons plus
the Chern-Simons gauge field. The family of solutions is parametrized by the 't
Hooft coupling. At special parity preserving points we get the critical O(N)
models, both the Wilson-Fisher one and the Gross-Neveu one. Our analysis also
fixes the on shell three point functions of Vasiliev's theory on AdS_4 or dS_4.Comment: 54 pages, 3 figure
Charge Form Factor and Cluster Structure of Li Nucleus
The charge form factor of Li nucleus is considered on the basis of its
cluster structure. The charge density of Li is presented as a
superposition of two terms. One of them is a folded density and the second one
is a sum of He and the deuteron densities. Using the available
experimental data for He and deuteron charge form factors, a good
agreement of the calculations within the suggested scheme is obtained with the
experimental data for the charge form factor of Li, including those in
the region of large transferred momenta.Comment: 12 pages 5 figure
Measurement of electron-neutrino electron elastic scattering
The cross section for the elastic scattering reaction nu_e+e- -> nu_e+e- was
measured by the Liquid Scintillator Neutrino Detector using a mu+ decay-at-rest
nu_e beam at the Los Alamos Neutron Science Center. The standard model of
electroweak physics predicts a large destructive interference between the
charge current and neutral current channels for this reaction. The measured
cross section, sigma_{nu_e e-}=[10.1 +- 1.1(stat.) +- 1.0(syst.)]x E_{nu_e}
(MeV) x 10^{-45} cm^2, agrees well with standard model expectations. The
measured value of the interference parameter, I=-1.01 +- 0.13(stat.) +-
0.12(syst.), is in good agreement with the standard model expectation of
I^{SM}=-1.09. Limits are placed on neutrino flavor-changing neutral currents.
An upper limit on the muon-neutrino magnetic moment of 6.8 x 10^{-10} mu_{Bohr}
is obtained using the nu_mu and \bar{nu}_mu fluxes from pi+ and mu+ decay.Comment: 22 pages, 11 figure
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