7,230 research outputs found
K* vector and tensor couplings from Nf = 2 tmQCD
The mass m_K* and vector coupling f_K* of the K*-meson, as well as the ratio
of the tensor to vector couplings fT/fV|_K*, are computed in lattice QCD. Our
simulations are performed in a partially quenched setup, with two dynamical
(sea) Wilson quark flavours, having a maximally twisted mass term. Valence
quarks are either of the standard or the Osterwalder-Seiler maximally twisted
variety. Results obtained at three values of the lattice spacing are
extrapolated to the continuum, giving m_K* = 981(33) MeV, f_K* = 240(18) MeV
and fT(2 GeV)/fV|_K* = 0.704(41).Comment: 1+11 page
Dark Matter in Theories of Gauge-Mediated Supersymmetry Breaking
In gauge-mediated theories supersymmetry breaking originates in a strongly
interacting sector and is communicated to the ordinary sparticles via
SU(3)SU(2)U(1) carrying ``messenger'' particles. Stable baryons
of the strongly interacting supersymmetry breaking sector naturally weigh
100 TeV and are viable cold dark matter candidates. They interact too
weakly to be observed in dark matter detectors. The lightest messenger particle
is a viable cold dark matter candidate under particular assumptions. It weighs
less than 5 TeV, has zero spin and is easily observable in dark matter
detectors.Comment: 10 pages, Late
Improving Mobile Video Streaming with Mobility Prediction and Prefetching in Integrated Cellular-WiFi Networks
We present and evaluate a procedure that utilizes mobility and throughput
prediction to prefetch video streaming data in integrated cellular and WiFi
networks. The effective integration of such heterogeneous wireless technologies
will be significant for supporting high performance and energy efficient video
streaming in ubiquitous networking environments. Our evaluation is based on
trace-driven simulation considering empirical measurements and shows how
various system parameters influence the performance, in terms of the number of
paused video frames and the energy consumption; these parameters include the
number of video streams, the mobile, WiFi, and ADSL backhaul throughput, and
the number of WiFi hotspots. Also, we assess the procedure's robustness to time
and throughput variability. Finally, we present our initial prototype that
implements the proposed approach.Comment: 7 pages, 15 figure
Layered Higgs Phase as a Possible Field Localisation on a Brane
So far it has been found by using lattice techniques that in the anisotropic
five--dimensional Abelian Higgs model, a layered Higgs phase exists in addition
to the expected five--dimensional one. The exploration of the phase diagram has
shown that the two Higgs phases are separated by a phase transition from the
confining phase. This transition is known to be first order. In this paper we
explore the possibility of finding a second order transition point in the
critical line which separates the first order phase transition from the
crossover region. This is shown to be the case only for the four--dimensional
Higgs layered phase whilst the phase transition to the five--dimensional broken
phase remains first order. The layered phase serves as the possible realisation
of four--dimensional spacetime dynamics which is embedded in a
five--dimensional spacetime. These results are due to gauge and scalar field
localisation by confining interactions along the extra fifth direction.Comment: 1+15 pages, 12 figure
O(a^2) cutoff effects in lattice Wilson fermion simulations
In this paper we propose to interpret the large discretization artifacts
affecting the neutral pion mass in maximally twisted lattice QCD simulations as
O(a^2) effects whose magnitude is roughly proportional to the modulus square of
the (continuum) matrix element of the pseudoscalar density operator between
vacuum and one-pion state. The numerical size of this quantity is determined by
the dynamical mechanism of spontaneous chiral symmetry breaking and turns out
to be substantially larger than its natural magnitude set by the value of
Lambda_QCD.Comment: 38 pages, 1 figure, 2 table
Particle Production of Vector Fields: Scale Invariance is Attractive
In a model of an Abelian vector boson with a Maxwell kinetic term and non-negative mass-squared it is demonstrated that, under fairly general conditions during inflation, a scale-invariant spectrum of perturbations for the components of a vector field, massive or not, whose kinetic function (and mass) is modulated by the inflaton field is an attractor solution. If the field is massless, or if it remains light until the end of inflation, this attractor solution also generates anisotropic stress, which can render inflation weakly anisotropic. The above two characteristics of the attractor solution can source (independently or combined together) significant statistical anisotropy in the curvature perturbation, which may well be observable in the near future
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