1,003 research outputs found
Moir\'e patterns in quantum images
We observed moir\'e fringes in spatial quantum correlations between twin
photons generated by parametric down-conversion. Spatially periodic structures
were nonlocally superposed giving rise to beat frequencies typical of moir\'e
patterns. This result brings interesting perspectives regarding metrological
applications of such a quantum optical setup.Comment: 4 pages, 5 figure
The strong coupling constant from lattice QCD with N_f=2 dynamical quarks
We compute for two flavors of light dynamical quarks
using non-perturbatively improved Wilson fermions. We improve on a
recent calculation by employing Pad\'e-improved two-loop and three-loop
perturbation theory to convert the lattice numbers to the scheme.Comment: Contribution to Lattice 2001 (matrix elements), typo correcte
Light hadron spectroscopy with O(a) improved dynamical fermions
We present the first results for the static quark potential and the light
hadron spectrum using dynamical fermions at using an O(a) improved
Wilson fermion action together with the standard Wilson plaquette action for
the gauge part. Sea quark masses were chosen such that the pseudoscalar-vector
mass ratio, m_PS/m_V$, varies from 0.86 to 0.67. Finite-size effects are
studied by using three different volumes, 8^3\cdot 24, 12^3\cdot 24 and
16^3\cdot 24. Comparing our results to previous ones obtained using the
quenched approximation, we find evidence for sea quark effects in quantities
like the static quark potential and the vector-pseudoscalar hyperfine
splitting.Comment: 38 pages, 14 Postscript figure, LaTe
Burst-induced spin variations in the accreting magnetic white dwarf PBC J0801.2–4625
PBC J0801.2–4625 is an intermediate polar with a primary spin frequency of 66.08 d−1 and an unknown orbital period. The long-term All Sky Automated Survey for Supernovae (ASAS-SN) light curve of this system reveals four bursts, all of which have similar peak amplitudes (∼2 mag) and durations (∼2 d). In this work, we primarily study the timing properties of this system’s 2019 February burst, which was simultaneously observed by both ASAS-SN and the Transiting Exoplanet Survey Satellite (TESS). Pre-burst, a frequency of 4.064 ± 0.002 d−1(5.906 ± 0.003 h period), likely attributed to the binary orbit, is identified in addition to previous measurements for the white dwarf’s spin. During the burst, however, we find a spin frequency of 68.35 ± 0.28 d−1. Post-burst, the spin returns to its pre-brust value but with a factor 1.82 ± 0.05 larger amplitude. The burst profile is double-peaked, and we estimate its energy to be 3.3 × 1039 erg. We conclude that the burst appears most consistent with thermonuclear runaway (i.e. a 'micronova'), and suggest that the spin variations may be an analogue to burst oscillations (i.e. 'micronova oscillations'). However, we also note that the above findings could be explained by a dwarf nova outburst. With the available data, we are unable to distinguish between these two scenarios
Development of a Time Efficient Protocol for Cross-Limb Comparisons of Muscle Mitochondrial Capacity Using NIRS
Click the PDF icon to download the abstract
The Kentucky Noisy Monte Carlo Algorithm for Wilson Dynamical Fermions
We develop an implementation for a recently proposed Noisy Monte Carlo
approach to the simulation of lattice QCD with dynamical fermions by
incorporating the full fermion determinant directly. Our algorithm uses a
quenched gauge field update with a shifted gauge coupling to minimize
fluctuations in the trace log of the Wilson Dirac matrix. The details of tuning
the gauge coupling shift as well as results for the distribution of noisy
estimators in our implementation are given. We present data for some basic
observables from the noisy method, as well as acceptance rate information and
discuss potential autocorrelation and sign violation effects. Both the results
and the efficiency of the algorithm are compared against those of Hybrid Monte
Carlo.
PACS Numbers: 12.38.Gc, 11.15.Ha, 02.70.Uu Keywords: Noisy Monte Carlo,
Lattice QCD, Determinant, Finite Density, QCDSPComment: 30 pages, 6 figure
A Study of the \eta \pi^{0} Spectrum and Search for a J^{PC} = 1^{-+} Exotic Meson
A partial wave analysis (PWA) of the of the system (where ) produced in the charge exchange reaction at an incident momentum of 18 GeV is presented as a function of
invariant mass, , and momentum transfer squared,
, from the incident to the outgoing system. , and waves were included in the PWA. The
and states are clearly observed in the overall
effective mass distribution as well as in the amplitudes associated with
wave and waves respectively after partial wave decomposition. The observed
distributions in moments (averages of spherical harmonics) were compared to the
results from the PWA and the two are consistent. The distribution in
for individual waves associated with natural and
unnatural parity exchange in the -channel are consistent with Regge
phenomenology. Of particular interest in this study is the wave since this
leads to an exotic for the system. A wave is
present in the data, however attempts to describe the mass dependence of the
amplitude and phase motion with respect to the wave as a Breit-Wigner
resonance are problematic. This has implications regarding the existence of a
reported exotic meson decaying into with a mass
near 1.4 GeV.Comment: 19 pages, 29 figures, to appear in Phys. Rev.
Speeding up finite step-size updating of full QCD on the lattice
We propose various improvements of finite step-size updating for full QCD on
the lattice that might turn finite step-size updating into a viable alternative
to the hybrid Monte Carlo algorithm. These improvements are noise reduction of
the noisy estimator of the fermion determinant, unbiased inclusion of the
hopping parameter expansion and a multi-level Metropolis scheme. First
numerical tests are performed for the 2 dimensional Schwinger model with two
flavours of Wilson fermions and for QCD two flavours of Wilson fermions and
Schr"odinger functional boundary conditions.Comment: 22 pages, 1 figur
Effects of non-perturbatively improved dynamical fermions in QCD at fixed lattice spacing
We present results for the static inter-quark potential, lightest glueballs,
light hadron spectrum and topological susceptibility using a non-perturbatively
improved action on a lattice at a set of values of the bare
gauge coupling and bare dynamical quark mass chosen to keep the lattice size
fixed in physical units ( fm). By comparing these measurements with a
matched quenched ensemble, we study the effects due to two degenerate flavours
of dynamical quarks. With the greater control over residual lattice spacing
effects which these methods afford, we find some evidence of charge screening
and some minor effects on the light hadron spectrum over the range of quark
masses studied (). More substantial differences between
quenched and unquenched simulations are observed in measurements of topological
quantities.Comment: 53 pages, LaTeX/RevTeX, 16 eps figures; corrected clover action
expression and various typos, no results change
A partial wave analysis of the system produced in charge exchange collisions
A partial wave analysis of the of the system produced in the
charge exchange reaction: at an incident momentum of
is presented as a function of invariant mass,
, and momentum transfer squared, , from the incident
to the outgoing system.Comment: 24 pages total,8 pages text, 14 figures, 1 table. Submitted to Phys
Rev
- …