7,836 research outputs found
Finite isospin density probe for conformality
A new method of employing an isospin chemical potential for QCD-like theories
with different number of colors, number of fermion flavors, and in different
fermion representations is proposed. The isospin chemical potential, which can
be simulated on the lattice due to its positive definite determinant gives a
means to probe both confining theories and IR conformal theories without
adjusting the lattice spacing and size. As the quark mass is reduced, the
isospin chemical potential provides an avenue to extract the chiral condensate
in confining theories through the resulting pseudoscalar condensate. For IR
conformal theories, the mass anomalous dimension can be extracted in the
conformal window through "finite density" scaling since the isospin chemical
potential is coupled to a conserved current. In both of these approaches, the
isospin chemical potential can be continuously varied for each ensemble at
comparable costs while maintaining the hierarchy between the lattice size and
lattice spacing. In addition to exploring these methods, finite volume and
lattice spacing effects are investigated.Comment: 18 pages, 3 figures, v3: typos corrected and discussions improved.
Phys. Rev. D 85, 074503 (2012
Characterizing the Galactic Gravitational Wave Background with LISA
We present a Monte Carlo simulation for the response of the Laser
Interferometer Space Antenna (LISA) to the galactic gravitational wave
background. The simulated data streams are used to estimate the number and type
of binary systems that will be individually resolved in a 1-year power
spectrum. We find that the background is highly non-Gaussian due to the
presence of individual bright sources, but once these sources are identified
and removed, the remaining signal is Gaussian. We also present a new estimate
of the confusion noise caused by unresolved sources that improves on earlier
estimates.Comment: 32 pages, 14 figures. Version to appear in PR
Lattice Simulations and Infrared Conformality
We examine several recent lattice-simulation data sets, asking whether they
are consistent with infrared conformality. We observe, in particular, that for
an SU(3) gauge theory with 12 Dirac fermions in the fundamental representation,
recent simulation data can be described assuming infrared conformality. Lattice
simulations include a fermion mass m which is then extrapolated to zero, and we
note that this data can be fit by a small-m expansion, allowing a controlled
extrapolation. We also note that the conformal hypothesis does not work well
for two theories that are known or expected to be confining and chirally
broken, and that it does work well for another theory expected to be infrared
conformal.Comment: 6 pages, 4 figures. v2: added new fit including finite-volume
corrections. v3: updated to match published versio
B529: Blossom and Twig Blight of Low-bush Blueberries (Botrytis cinerea)
This bulletin presents the results of research on three aspects of the disease blossom and twig blight, (1) seasonal development, (2) the effect of environmental factors, and (3) chemical control. The work was supported financially by Maine Blueberry Tax funds.https://digitalcommons.library.umaine.edu/aes_bulletin/1084/thumbnail.jp
Measurement Error in Estimates of Sprint Velocity from a Laser Displacement Measurement Device
This study aimed to determine the measurement error associated with estimates of velocity from a laser-based device during different phases of a maximal athletic sprint. Laser-based displacement data were obtained from 10 sprinters completing a total of 89 sprints and were fitted with a fifth-order polynomial function which was differentiated to obtain instantaneous velocity data. These velocity estimates were compared against criterion high-speed video velocities at either 1, 5, 10, 30 or 50 m using a Bland-Altman analysis to assess bias and random error. Bias was highest at 1 m (+ 0.41 m/s) and tended to decrease as the measurement distance increased, with values less than + 0.10 m/s at 30 and 50 m. Random error was more consistent between distances, and reached a minimum value (±0.11 m/s) at 10 m. Laser devices offer a potentially useful time-efficient tool for assessing between-subject or between-session performance from the mid-acceleration and maximum velocity phases (i. e., at 10 m and beyond), although only differences exceeding 0.22-0.30 m/s should be considered genuine. However, laser data should not be used during the first 5 m of a sprint, and are likely of limited use for assessing within-subject variation in performance during a single session
IR Monitoring of the Microquasar GRS 1915+105: Detection of Orbital and Superhump Signatures
We present the results of seven years of K-band monitoring of the low-mass
X-ray binary GRS 1915+105. Positive correlations between the infrared flux and
the X-ray flux and X-ray hardness are demonstrated. Analysis of the frequency
spectrum shows that the orbital period of the system is
days. The phase and amplitude of the orbital modulation suggests that the
modulation is due to the heating of the face of the secondary star. We also
report another periodic signature between 31.2 and 31.6 days, most likely due
to a superhump resonance. From the superhump period we then obtain a range on
the mass ratio of the system, .Comment: 16 pages, 6 figures; v2: minor change
Lattice simulations with eight flavors of domain wall fermions in SU(3) gauge theory
We study an SU(3) gauge theory with Nf=8 degenerate flavors of light fermions
in the fundamental representation. Using the domain wall fermion formulation,
we investigate the light hadron spectrum, chiral condensate and electroweak S
parameter. We consider a range of light fermion masses on two lattice volumes
at a single gauge coupling chosen so that IR scales approximately match those
from our previous studies of the two- and six-flavor systems. Our results for
the Nf=8 spectrum suggest spontaneous chiral symmetry breaking, though fits to
the fermion mass dependence of spectral quantities do not strongly disfavor the
hypothesis of mass-deformed infrared conformality. Compared to Nf=2 we observe
a significant enhancement of the chiral condensate relative to the symmetry
breaking scale F, similar to the situation for Nf=6. The reduction of the S
parameter, related to parity doubling in the vector and axial-vector channels,
is also comparable to our six-flavor results
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