1,074 research outputs found
Exclusive Queueing Process with Discrete Time
In a recent study [C Arita, Phys. Rev. E 80, 051119 (2009)], an extension of
the M/M/1 queueing process with the excluded-volume effect as in the totally
asymmetric simple exclusion process (TASEP) was introduced. In this paper, we
consider its discrete-time version. The update scheme we take is the parallel
one. A stationary-state solution is obtained in a slightly arranged matrix
product form of the discrete-time open TASEP with the parallel update. We find
the phase diagram for the existence of the stationary state. The critical line
which separates the parameter space into the regions with and without the
stationary state can be written in terms of the stationary current of the open
TASEP. We calculate the average length of the system and the average number of
particles
Beyond paired quantum Hall states: parafermions and incompressible states in the first excited Landau level
The Pfaffian quantum Hall states, which can be viewed as involving pairing
either of spin-polarized electrons or of composite fermions, are generalized by
finding the exact ground states of certain Hamiltonians with k+1-body
interactions, for all integers k > 0. The remarkably simple wavefunctions of
these states involve clusters of k particles, and are related to correlators of
parafermion currents in two-dimensional conformal field theory. The k=2 case is
the Pfaffian. For k > 1, the quasiparticle excitations of these systems are
expected to possess nonabelian statistics, like those of the Pfaffian. For k=3,
these ground states have large overlaps with the ground states of the (2-body)
Coulomb-interaction Hamiltonian for electrons in the first excited Landau level
at total filling factors \nu=2+3/5, 2+2/5.Comment: 11 pages Revtex in two column format with 4 eps figures included in
the M
On Delays in Management Frameworks: Metrics, Models and Analysis
Management performance evaluation means assessment of scalability, complexity, accuracy, throughput, delays and resources consumptions. In this paper, we focus on the evaluation of management frameworks delays through a set of specific metrics. We investigate the statistical properties of these metrics when the number of management nodes increases. We show that management delays measured at the application level are statistically modeled by distributions with heavy tails, especially the Weibull distribution. Given that delays can substantially degrade the capacity of management algorithms to react and resolve problems it is useful to get a finer model to describe them.We suggest theWeibull distribution as a model of delays for the analysis and simulations of such algorithms
New physics, the cosmic ray spectrum knee, and cross section measurements
We explore the possibility that a new physics interaction can provide an
explanation for the knee just above GeV in the cosmic ray spectrum. We
model the new physics modifications to the total proton-proton cross section
with an incoherent term that allows for missing energy above the scale of new
physics. We add the constraint that the new physics must also be consistent
with published cross section measurements, using cosmic ray observations,
an order of magnitude and more above the knee. We find that the rise in cross
section required at energies above the knee is radical. The increase in cross
section suggests that it may be more appropriate to treat the scattering
process in the black disc limit at such high energies. In this case there may
be no clean separation between the standard model and new physics contributions
to the total cross section. We model the missing energy in this limit and find
a good fit to the Tibet III cosmic ray flux data. We comment on testing the new
physics proposal for the cosmic ray knee at the Large Hadron Collider.Comment: 17 pages, 4 figure
Energy, interaction, and photoluminescence of spin-reversed quasielectrons in fractional quantum Hall systems
The energy and photoluminescence spectra of a two-dimensional electron gas in
the fractional quantum Hall regime are studied. The single-particle properties
of reversed-spin quasielectrons (QE's) as well as the
pseudopotentials of their interaction with one another and with Laughlin
quasielectrons (QE's) and quasiholes (QH's) are calculated. Based on the
short-range character of the QE--QE and QE--QE
repulsion, the partially unpolarized incompressible states at the filling
factors and are postulated within Haldane's
hierarchy scheme. To describe photoluminescence, the family of bound
QE states of a valence hole and QE's are
predicted in analogy to the found earlier fractionally charged excitons
QE. The binding energy and optical selection rules for both families are
compared. The QE is found radiative in contrast to the dark QE,
and the QE is found non-radiative in contrast to the bright
QE.Comment: 9 pages, 6 figure
The Harris-Luck criterion for random lattices
The Harris-Luck criterion judges the relevance of (potentially) spatially
correlated, quenched disorder induced by, e.g., random bonds, randomly diluted
sites or a quasi-periodicity of the lattice, for altering the critical behavior
of a coupled matter system. We investigate the applicability of this type of
criterion to the case of spin variables coupled to random lattices. Their
aptitude to alter critical behavior depends on the degree of spatial
correlations present, which is quantified by a wandering exponent. We consider
the cases of Poissonian random graphs resulting from the Voronoi-Delaunay
construction and of planar, ``fat'' Feynman diagrams and precisely
determine their wandering exponents. The resulting predictions are compared to
various exact and numerical results for the Potts model coupled to these
quenched ensembles of random graphs.Comment: 13 pages, 9 figures, 2 tables, REVTeX 4. Version as published, one
figure added for clarification, minor re-wordings and typo cleanu
Color Transparency versus Quantum Coherence in Electroproduction of Vector Mesons off Nuclei
So far no theoretical tool for the comprehensive description of exclusive
electroproduction of vector mesons off nuclei at medium energies has been
developed. We suggest a light-cone QCD formalism which is valid at any energy
and incorporates formation effects (color transparency), the coherence length
and the gluon shadowing. At medium energies color transparency (CT) and the
onset of coherence length (CL) effects are not easily separated. Indeed,
although nuclear transparency measured by the HERMES experiment rises with Q^2,
it agrees with predictions of the vector dominance model (VDM) without any CT
effects. Our new results and observations are: (i) the good agreement with the
VDM found earlier is accidental and related to the specific correlation between
Q^2 and CL for HERMES kinematics; (ii) CT effects are much larger than have
been estimated earlier within the two channel approximation. They are even
stronger at low than at high energies and can be easily identified by HERMES or
at JLab; (iii) gluon shadowing which is important at high energies is
calculated and included; (iv) our parameter-free calculations explain well
available data for variation of nuclear transparency with virtuality and energy
of the photon; (v) predictions for electroproduction of \rho and \phi are
provided for future measurements at HERMES and JLab.Comment: Latex 57 pages and 17 figure
Higgs Scalars in the Minimal Non-minimal Supersymmetric Standard Model
We consider the simplest and most economic version among the proposed
non-minimal supersymmetric models, in which the -parameter is promoted to
a singlet superfield, whose all self-couplings are absent from the
renormalizable superpotential. Such a particularly simple form of the
renormalizable superpotential may be enforced by discrete -symmetries which
are extended to the gravity-induced non-renormalizable operators as well. We
show explicitly that within the supergravity-mediated supersymmetry-breaking
scenario, the potentially dangerous divergent tadpoles associated with the
presence of the gauge singlet first appear at loop levels higher than 5 and
therefore do not destabilize the gauge hierarchy. The model provides a natural
explanation for the origin of the -term, without suffering from the
visible axion or the cosmological domain-wall problem. Focusing on the Higgs
sector of this minimal non-minimal supersymmetric standard model, we calculate
its effective Higgs potential by integrating out the dominant quantum effects
due to stop squarks. We then discuss the phenomenological implications of the
Higgs scalars predicted by the theory for the present and future high-energy
colliders. In particular, we find that our new minimal non-minimal
supersymmetric model can naturally accommodate a relatively light charged Higgs
boson, with a mass close to the present experimental lower bound.Comment: 63 pages (12 figures), extended versio
Synthesis, antileishmanial activity and QSAR studies of 2-chloro- N -arylacetamides
ABSTRACT We describe herein the synthesis and evaluation of the antileishmanial activity against promastigote forms of Leishmania amazonensis and cytotoxicity to murine macrophages of a series of 2-chloro-N-arylacetamide derivatives. All compounds were active, except one (compound 3). Compound 5 presented the most promising results, showing good antileishmanial activity (CI50=5.39±0.67 µM) and moderate selectivity (SI=6.36), indicating that further development of this class is worthwhile. Preliminary QSAR studies, although not predictive, furnished some insights on the importance of electronic character of aryl substituent to biological activity, as well as an indirect influence of hydrophobicity on activity
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