1,445 research outputs found
Eigenvector localization for random band matrices with power law band width
It is shown that certain ensembles of random matrices with entries that
vanish outside a band around the diagonal satisfy a localization condition on
the resolvent which guarantees that eigenvectors have strong overlap with a
vanishing fraction of standard basis vectors, provided the band width
raised to a power remains smaller than the matrix size . For a
Gaussian band ensemble, with matrix elements given by i.i.d. centered Gaussians
within a band of width , the estimate holds.Comment: 30 pages; corrected typo
Mandelbrot set in coupled logistic maps and in an electronic experiment
We suggest an approach to constructing physical systems with dynamical
characteristics of the complex analytic iterative maps. The idea follows from a
simple notion that the complex quadratic map by a variable change may be
transformed into a set of two identical real one-dimensional quadratic maps
with a particular coupling. Hence, dynamical behavior of similar nature may
occur in coupled dissipative nonlinear systems, which relate to the Feigenbaum
universality class. To substantiate the feasibility of this concept, we
consider an electronic system, which exhibits dynamical phenomena intrinsic to
complex analytic maps. Experimental results are presented, providing the
Mandelbrot set in the parameter plane of this physical system.Comment: 9 pages, 3 figure
production in PHENIX
Heavy quarkonia production is expected to be sensitive to the formation of a
quark gluon plasma (QGP). The PHENIX experiment has measured
production at ~200 GeV in Au+Au and Cu+Cu collisions, as well
as in reference p+p and d+Au runs. 's were measured both at mid
() and forward () rapidity. In this letter, we present
the A+A preliminary results and compare them to normal cold nuclear matter
expectations derived from PHENIX d+Au and p+p measurements as well as to
theoretical models including various effects (color screening, recombination,
sequential melting...).Comment: 5 pages, 7 figures. To appear in the proceedings of Hot Quarks 2006:
Workshop for Young Scientists on the Physics of Ultrarelativistic
Nucleus-Nucleus Collisions, Villasimius, Italy, 15-20 May 200
On The Low Frequency Quasi Periodic Oscillations of X-ray Sources
Based on the interpretation of the twin kilohertz Quasi Periodic Oscillations
(kHz QPOs) of X-ray spectra of Low Mass X-Ray Binaries
(LMXBs) to the Keplerian and the periastron precession frequencies at the
magnetosphere-disk of X-ray neutron star (NS) respectively, we ascribe the low
frequency Quasi Periodic Oscillations (LFQPO) and HBO (15-60 Hz QPO for Z
sources or Atoll sources) to the periastron precession at some outer disk
radius.
The obtained conclusions include: all QPO frequencies increase with
increasing the accretion rate. The obtained theoretical relations between HBO
(LFQPO) frequency and the kHz QPO frequency are similar to the measured
empirical formula. Further, the possible dynamical mechanism for QPO production
is discussed.Comment: 6 pages, 2 figures, accepted by APSS, 200
Quark States near a Threshold and the Unstable H-dibaryon
We consider the interplay of a quark state and a hadronic threshold in the
framework of the P-matrix formalism, which is reviewed and extended for use
together with conventional methods of computing quark-gluon dynamics. We
provide a quantitative dynamical interpretation of the reduced R or K matrices
and their poles that suggests a natural classification of threshold phenomena.
At a threshold with a quark state close to it up to three S-matrix poles can be
found. The scattering amplitudes for the corresponding cases are discussed. Our
analysis is applied to make an outlook for experimental observation of the
doubly strange H-dibaryon if it is not stable to strong decays.Comment: 28 pages, 7 figures, RevTeX, uses aps.sty, fps.st
START in a five-dimensional conformal domain
In this paper we give a brief review of the pseudo-Riemannian geometry of the
five-dimensional homogeneous space for the conformal group O(4,2). Its topology
is described and its relation to the conformally compactified Minkowski space
is described. Its metric is calculated using a generalized half-space
representation. Compactification via Lie-sphere geometry is outlined. Possible
applications to Jaime Keller's START theory may follow by using its predecessor
- the 5-optics of Yu. B. Rumer. The point of view of Rumer is given extensively
in the last section of the paper.
Keywords. Kaluza,Klein, Rumer, conformal symmetry, hyperbolic space, START,
fifth dimension, action coordinate, 5-opticsComment: Latex, 13 pages, 3 figures, added sections 3.2. Christoffel symbols
and geodesics and 3.3. {\Sigma}- as the space of hyperboloids; accepted for
publication in the special volume of AACA in memory of Prof. Jaime Kelle
G(2) quivers
We present, in explicit matrix representation and a modernity befitting the community, the classification of the finite discrete subgroups of G2 and compute the McKay quivers arising therefrom. Of physical interest are the classes of Script N = 1 gauge theories descending from M-theory and of mathematical interest are possible steps toward a systematic study of crepant resolutions to smooth G2 manifolds as well as generalised McKay Correspondences. This writing is a companion monograph to hep-th/9811183 and hep-th/9905212, wherein the analogues for Calabi-Yau three- and four-folds were considered
Gauged motion in general relativity and in Kaluza-Klein theories
In a recent paper [1] a new generalization of the Killing motion, the {\it
gauged motion}, has been introduced for stationary spacetimes where it was
shown that the physical symmetries of such spacetimes are well described
through this new symmetry. In this article after a more detailed study in the
stationary case we present the definition of gauged motion for general
spacetimes. The definition is based on the gauged Lie derivative induced by a
threading family of observers and the relevant reparametrization invariance. We
also extend the gauged motion to the case of Kaluza-Klein theories.Comment: 42 pages, revised version, typos correction along with some minor
changes, Revtex forma
Photon-Photon and Pomeron-Pomeron Processes in Peripheral Heavy Ion Collisions
We estimate the cross sections for the production of resonances, pion pairs
and a central cluster of hadrons in peripheral heavy-ion collisions through
two-photon and double-pomeron exchange, at energies that will be available at
RHIC and LHC. The effect of the impact parameter in the diffractive reactions
is introduced, and imposing the condition for realistic peripheral collisions
we verify that in the case of very heavy ions the pomeron-pomeron contribution
is indeed smaller than the electromagnetic one. However, they give a
non-negligible background in the collision of light ions. This diffractive
background will be more important at RHIC than at LHC.Comment: 22 pages, 1 Postscript figures, 4 tables, to appear in Phys. Rev.
Resonance approximation and charge loading/unloading in adiabatic quantum pumping
Quantum pumping through mesoscopic quantum dots is known to be enhanced by
resonant transmission. The pumped charge is close to an integer number of
electrons when the pumping contour surrounds a resonance, but the transmission
remains small on the contour. For non-interacting electrons, we give a
quantitative account of the detailed exchange of electrons between the dot and
the leads (to the electron reservoirs) during a pumping cycle. Near isolated
distinct resonances, we use approximate Breit-Wigner expressions for the dot's
Green function to discuss the loading/unloading picture of the pumping: the
fractional charge exchanged between the dot and each lead through a single
resonance point is related to the relative couplings of the dot and the leads
at this resonance. If each resonance point along the pumping contour is
dominated by the coupling to a single lead (which also implies a very small
transmission), then the crossing of each such resonance results in a single
electron exchange between the dot and that lead, ending up with a net quantized
charge. When the resonance approximation is valid, the fractional charges can
also be extracted from the peaks of the transmissions between the various
leads.Comment: 10 pages, 4 figure
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