3,608 research outputs found
Multicanonical Study of the 3D Ising Spin Glass
We simulated the Edwards-Anderson Ising spin glass model in three dimensions
via the recently proposed multicanonical ensemble. Physical quantities such as
energy density, specific heat and entropy are evaluated at all temperatures. We
studied their finite size scaling, as well as the zero temperature limit to
explore the ground state properties.Comment: FSU-SCRI-92-121; 7 pages; sorry, no figures include
A New Approach to Spin Glass Simulations
We present a recursive procedure to calculate the parameters of the recently
introduced multicanonical ensemble and explore the approach for spin glasses.
Temperature dependence of the energy, the entropy and other physical quantities
are easily calculable and we report results for the zero temperature limit. Our
data provide evidence that the large increase of the ergodicity time is
greatly improved. The multicanonical ensemble seems to open new horizons for
simulations of spin glasses and other systems which have to cope with
conflicting constraints
Discovery of Delta Scuti variables in eclipsing binary systems II.Southern TESS field search
The presence of pulsating stars in eclipsing binary systems (EBs) makes these
objects significant since they allow us to investigate the stellar interior
structure and evolution. Different types of pulsating stars could be found in
EBs such as Delta Scuti variables. Delta Scuti stars in EBs have been known for
decades and the increasing number of such systems is important for
understanding pulsational structure. Hence, in this study, a research was
carried out on the southern TESS field to discover new Delta Scuti stars in
EBs. We produced an algorithm to search for detached and semi-detached EBs
considering three steps; the orbital period (P)'s harmonics in the
Fourier spectrum, skewness of the light curves, and classification of
\textsc{UPSILON} program. If two of these steps classify a system as an EB, the
algorithm also identifies it as an EB. The TESS pixel files of targets were
also analyzed to see whether the fluxes are contaminated by other systems. No
contamination was found. We researched the existence of pulsation through EBs
with a visual inspection. To confirm Delta Scuti-type oscillations, the binary
variation was removed from the light curve, and residuals were analyzed.
Consequently, we identified 42 Delta Scuti candidates in EBs. The P,
, and M of systems were calculated. Their positions on the H-R diagram
and the known orbital-pulsation period relationship were analyzed. We also
examined our targets to find if any of them show frequency modulation with the
orbital period and discovered one candidate of tidally tilted pulsators.Comment: Published in MNRA
How large is "large " for Nuclear matter?
We argue that a so far neglected dimensionless scale, the number of neighbors
in a closely packed system, is relevant for the convergence of the large
expansion at high chemical potential. It is only when the number of colors is
large w.r.t. this new scale (\sim \order{10}) that a convergent large
limit is reached. This provides an explanation as to why the large
expansion, qualitatively successful in in vacuum QCD, fails to describe high
baryo-chemical potential systems, such as nuclear matter. It also means that
phenomenological claims about high density matter based on large
extrapolations should be treated with caution.Comment: Proceedings of CPOD2010 conference, in Dubna. Results based on
Phys.Rev.C82, 055202 (2010), http://arxiv.org/abs/1006.247
Explaining spatial variation in housing construction activity in Turkey
In Turkey, there has been a strong policy narrative that has emphasized the importance of construction activity as a driver of economic growth. This has given shape to a central state-led policy regime that has sought to ensure that planners and other urban policy makers develop plans and strategies that support construction activity. Against this backdrop, and a recent history of uneven spatial development, this paper seeks to understand what this policy imperative might mean for housing construction activity in different provinces. It seeks to reflect on both the relationship between the state and the market, and the interaction between state policies, economic drivers and levels of construction activity. The evidence presented in the paper suggests that uneven spatial development might be explained in different ways in different provinces. Although, in many cases, patterns of construction activity are consistent with economic fundamentals, there are important exceptions in some regions where arguably activity levels are at odds with prior expectations
Three Millisecond Pulsars in FERMI LAT Unassociated Bright Sources
We searched for radio pulsars in 25 of the non-variable, unassociated sources
in the Fermi LAT Bright Source List with the Green Bank Telescope at 820 MHz.
We report the discovery of three radio and gamma-ray millisecond pulsars (MSPs)
from a high Galactic latitude subset of these sources. All of the pulsars are
in binary systems, which would have made them virtually impossible to detect in
blind gamma-ray pulsation searches. They seem to be relatively normal, nearby
(<=2 kpc) millisecond pulsars. These observations, in combination with the
Fermi detection of gamma-rays from other known radio MSPs, imply that most, if
not all, radio MSPs are efficient gamma-ray producers. The gamma-ray spectra of
the pulsars are power-law in nature with exponential cutoffs at a few GeV, as
has been found with most other pulsars. The MSPs have all been detected as
X-ray point sources. Their soft X-ray luminosities of ~10^{30-31} erg/s are
typical of the rare radio MSPs seen in X-rays.Comment: Accepted for publication in ApJ Letter
Frustration - how it can be measured
A misfit parameter is used to characterize the degree of frustration of
ordered and disordered systems. It measures the increase of the ground-state
energy due to frustration in comparison with that of a relevant reference
state. The misfit parameter is calculated for various spin-glass models. It
allows one to compare these models with each other. The extension of this
concept to other combinatorial optimization problems with frustration, e.g.
p-state Potts glasses, graph-partitioning problems and coloring problems is
given.Comment: 10 pages, 1 table, no figures, uses revtex.st
Observation and Spectral Measurements of the Crab Nebula with Milagro
The Crab Nebula was detected with the Milagro experiment at a statistical
significance of 17 standard deviations over the lifetime of the experiment. The
experiment was sensitive to approximately 100 GeV - 100 TeV gamma ray air
showers by observing the particle footprint reaching the ground. The fraction
of detectors recording signals from photons at the ground is a suitable proxy
for the energy of the primary particle and has been used to measure the photon
energy spectrum of the Crab Nebula between ~1 and ~100 TeV. The TeV emission is
believed to be caused by inverse-Compton up-scattering scattering of ambient
photons by an energetic electron population. The location of a TeV steepening
or cutoff in the energy spectrum reveals important details about the underlying
electron population. We describe the experiment and the technique for
distinguishing gamma-ray events from the much more-abundant hadronic events. We
describe the calculation of the significance of the excess from the Crab and
how the energy spectrum is fit. The fit is consistent with values measured by
IACTs between 1 and 20 TeV. Fixing the spectral index to values that have been
measured below 1 TeV by IACT experiments (2.4 to 2.6), the fit to the Milagro
data suggests that Crab exhibits a spectral steepening or cutoff between about
20 to 40 TeV.Comment: Submitted to Astrophysical Journa
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