167,353 research outputs found
Statistics of mixing in three-dimensional Rayleigh--Taylor turbulence at low Atwood number and Prandtl number one
Three-dimensional miscible Rayleigh--Taylor (RT) turbulence at small Atwood
number and at Prandtl number one is investigated by means of high resolution
direct numerical simulations of the Boussinesq equations. RT turbulence is a
paradigmatic time-dependent turbulent system in which the integral scale grows
in time following the evolution of the mixing region. In order to fully
characterize the statistical properties of the flow, both temporal and spatial
behavior of relevant statistical indicators have been analyzed.
Scaling of both global quantities ({\it e.g.}, Rayleigh, Nusselt and Reynolds
numbers) and scale dependent observables built in terms of velocity and
temperature fluctuations are considered. We extend the mean-field analysis for
velocity and temperature fluctuations to take into account intermittency, both
in time and space domains. We show that the resulting scaling exponents are
compatible with those of classical Navier--Stokes turbulence advecting a
passive scalar at comparable Reynolds number. Our results support the scenario
of universality of turbulence with respect to both the injection mechanism and
the geometry of the flow
Electromagnetic Form Factors and the Hypercentral CQM
New results about the electromagnetic form factors of the nucleon are
obtained with a semirelativistic version of the hypercentral constituent quark
model (hCQM) and a relativistic current. The complex structure of the
constituent quarks is taken into account implicitly by means of
phenomenological constituent quark form factors. We obtain a detailed
reproduction of the experimental data up to , moreover our findings
about constituent quark root mean square radii are of the same order than the
recent ones obtained analyzing the proton structure functions.Comment: 11 pages, 4 figure
John Bell Across Space and Time
This is a review of the book Quantum [Un]speakables: From Bell to Quantum
Information. Reinhold A. Bertlmann and Anton Zeilinger (editors).Comment: 4 pages LaTe
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
Search for pentaquark in high statistics measurement of at CLAS
The exclusive reaction was studied in the
photon energy range between 1.6-3.8 GeV searching for evidence of the exotic
baryon . The decay to requires the assignment of
strangeness to any observed resonance. Data were collected with the CLAS
detector at the Thomas Jefferson National Accelerator Facility corresponding to
an integrated luminosity of 70 . No evidence for the
pentaquark was found. Upper limits were set on the production cross section as
function of center-of-mass angle and mass. The 95% CL upper limit on the
total cross section for a narrow resonance at 1540 MeV was found to be 0.8 nb.Comment: Submitted to Physical Review Letter
A finite temperature investigation of dual superconductivity in the modified SO(3) lattice gauge theory
We study the SO(3) lattice gauge theory in 3+1 dimensions with the adjoint
Wilson action modified by a monopole suppression term and by
means of the Pisa disorder operator. We find evidence for a finite temperature
deconfinement transition driven by the condensation of U(1) magnetic charges. A
finite-size scaling test shows consistency with the critical exponents of the
3D Ising model.Comment: 14 pages, 4 figures. Layout changed, figures, text and references
added. To appear on Physics Letters
Resonant Raman scattering by collective modes of the one-dimensional electron gas
We show that the low-energy peak in the polarized resonant Raman spectra of
quantum wires, which is commonly associated with ``single particle
excitations'', can be interpreted as signature of intra-band collective spin
excitations. A broad maximum in the resonant depolarized spectra is predicted
to exist above the frequency of the spin density excitation, due to
simultaneous but independent propagation of spin- and charge-density modes.Comment: 4 pages, accepted for publication in Phys. Rev. Let
Asymptotic tunneling conductance in Luttinger liquids
Conductance through weak constrictions in Luttinger liquids is shown to
vanish with frequency as , where
is a dimensionless parameter characterizing the Luttinger liquid phase, and
and are nonuniversal constants. The first term arises from the ^^
Coulomb blockade' effect and dominates for , whereas the second
results from eliminating high-energy modes and dominates for .Comment: Latex file + one appended postcript figur
Finite-top-mass effects in NNLO Higgs production
We construct an accurate approximation to the exact NNLO cross section for
Higgs production in gluon-gluon fusion by matching the dominant finite top mass
corrections recently computed by us to the known result in the infinite mass
limit. The ensuing corrections to the partonic cross section are very large
when the center of mass energy of the partonic collision is much larger than
the Higgs mass, but lead to a moderate correction at the percent level to the
total Higgs production cross section at the LHC. Our computation thus reduces
the uncertainty related to these corrections at the LHC from the percent to the
per mille level.Comment: 4 pages, 4 figures; to be published in the proceedings of QCD2008.
Reference adde
Adiabatically steered open quantum systems: Master equation and optimal phase
We introduce an alternative way to derive the generalized form of the master
equation recently presented by J. P. Pekola et al. [Phys. Rev. Lett. 105,
030401 (2010)] for an adiabatically steered two-level quantum system
interacting with a Markovian environment. The original derivation employed the
effective Hamiltonian in the adiabatic basis with the standard interaction
picture approach but without the usual secular approximation. Our approach is
based on utilizing a master equation for a non-steered system in the first
super-adiabatic basis. It is potentially efficient in obtaining higher-order
equations. Furthermore, we show how to select the phases of the adiabatic
eigenstates to minimize the local adiabatic parameter and how this selection
leads to states which are invariant under a local gauge change. We also discuss
the effects of the adiabatic noncyclic geometric phase on the master equation.Comment: 8 pages, no figures, final versio
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