8,944 research outputs found
On the strategy frequency problem in batch Minority Games
Ergodic stationary states of Minority Games with S strategies per agent can
be characterised in terms of the asymptotic probabilities with which
an agent uses of his strategies. We propose here a simple and general
method to calculate these quantities in batch canonical and grand-canonical
models. Known analytic theories are easily recovered as limiting cases and, as
a further application, the strategy frequency problem for the batch
grand-canonical Minority Game with S=2 is solved. The generalization of these
ideas to multi-asset models is also presented. Though similarly based on
response function techniques, our approach is alternative to the one recently
employed by Shayeghi and Coolen for canonical batch Minority Games with
arbitrary number of strategies.Comment: 17 page
Magnetic superlattice and finite-energy Dirac points in graphene
We study the band structure of graphene's Dirac-Weyl quasi-particles in a one-dimensional magnetic superlattice formed by a periodic sequence of alternating magnetic barriers. The spectrum and the nature of the states strongly depend on the conserved longitudinal momentum and on the barrier width. At the center of the superlattice Brillouin zone we find new Dirac points at finite energies where the dispersion is highly anisotropic, in contrast to the dispersion close to the neutrality point which remains isotropic. This finding suggests the possibility of collimating Dirac-Weyl quasi-particles by tuning the doping
Ideological Extremism, Conspiratorial Thought, and Support for Authoritarianism in the United States
Since the nation’s founding, Americans have tended to take democracy for granted. People see democracy as a given, believing that adherence to democratic values will persist. However, in the past few election cycles, there has been a trend in support for authoritarianism in the United States – not just with political leaders and figures, but also with individuals susceptible to authoritarian values and signals. This thesis seeks to address this apparent threat of authoritarianism in the United States, delving into possible factors that play a role in the growing support for authoritarian attitudes among Americans. I believe that two phenomena play a significant role in the rise in authoritarianism: conspiratorial thinking and ideological extremism, both of which have also grown increasingly prevalent. I theorize that conspiratorial thinking, ideological extremism, and authoritarianism are linked through a common ingroup/outgroup mentality that gives people a shared framework for how they relate to the political environment. Further, I examine whether conspiratorial thinking and ideological extremism can reinforce each other’s effects on support for authoritarianism. To assess these linkages, I utilized data from a national survey conducted in February 2021. My initial analysis shows support for one of my two hypotheses. Conspiratorial thinking has a significant and positive effect on authoritarianism; ideological extremism does not. Additional analysis shows that conspiratorial thinking and ideological extremism do, in fact, have a reinforcing effect on support for authoritarianism. These results suggest that there is no simple solution to addressing authoritarianism without addressing aspects of the political environment that contribute to conspiratorial thought and ideological extremism
Fixing Conditions in the Freeze Substitution Technique for Light Microscopy Observation of Frozen Beef Tissue
The freeze substitution histological technique allows the indirect light microscopicobservation and the quantitative evaluation of ice crystal size in frozen tissues. Theuseofchemical fixatives in substitu ting fluids improves morphological and histochemical preservation of the tissue. Fixation conditions become important since this step can introduce modifications in crystal sizes . Effects of temperature on: a) diffusion rate of fixing solution in tissue, b) recrystallization rate of ice in frozen beef and c) variations of the froze~ water fraction were ana lyzed, establishing that 1sothermal freeze fixation constitutes an appropriate method for histological observation. Fixing at temperatures lower than that of the sample, in an attempt to reduce recrystallization effects , involves an increase of the frozen water fraction i.n the tissue leading to modifications in size of ice crystals and to changes in the histological structure
IGR J00234+6141 : a new INTEGRAL source identified as an Intermediate polar
Following an extensive survey of the galactic plane by the INTEGRAL
satellite, new hard X-ray sources are discovered with a significant fraction of
Cataclysmic Variables (CVs) among them. We report here the identification of
one of these hard X-ray sources, IGR J00234+6141, as an accreting magnetic
white dwarf of intermediate polar type. We analyse the high energy emission of
the INTEGRAL source using all available data and provide complementary optical
photometric and spectroscopic data obtained respectively in August and October
2006. Based on a refined INTEGRAL position, we confirm the proposed optical
identification. We clearly detect the presence of a 564 s periodic optical
modulation that we identify as the rotation of the white dwarf. The analysis of
the optical spectrum also demonstrates that the emission lines show a
modulation in radial velocity with an orbital period of Porb = (4.033 +/-
0.005) hr. The two periodicities indicate that IGR00234+6141 is a magnetic CV
of the intermediate polar type. This is one of the faintest and hardest sources
of this type detected by INTEGRAL. This confirms earlier conclusions that IPs
contribute significantly to the population of galactic X-ray sources and
represent a significant fraction of the high energy background.Comment: 6 pages, 7 figures, accepted for publication in A&
Swift J0525.6+2416 and IGR J04571+4527: two new hard X-ray selected magnetic cataclysmic variables identified with XMM-Newton
IGR J04571+4527 and Swift J0525.6+2416 are two hard X-ray sources detected in
the Swift/BAT and INTEGRAL/IBIS surveys. They were proposed to be magnetic
cataclysmic variables of the Intermediate Polar (IP) type, based on optical
spectroscopy. IGR J04571+4527 also showed a 1218 s optical periodicity,
suggestive of the rotational period of a white dwarf, further pointing towards
an IP classification. We here present detailed X-ray (0.3-10 keV) timing and
spectral analysis performed with XMM-Newton, complemented with hard X-ray
coverage (15-70 keV) from Swift/BAT. These are the first high signal to noise
observations in the soft X-ray domain for both sources, allowing us to identify
the white dwarf X-ray spin period of Swift J0525.6+2416 (226.28 s), and IGR
J04571+4527 (1222.6 s). A model consisting of multi-temperature optically thin
emission with complex absorption adequately fits the broad-band spectrum of
both sources. We estimate a white dwarf mass of about 1.1 and 1.0 solar masses
for IGR J04571+4527 and Swift J0525.6+2416, respectively. The above
characteristics allow us to unambiguously classify both sources as IPs,
confirming the high incidence of this subclass among hard X-ray emitting
Cataclysmic Variables.Comment: 8 pages, 4 figures, 3 tables. Accepted for publication in MNRA
Controlled quantum evolutions and transitions
We study the nonstationary solutions of Fokker-Planck equations associated to
either stationary or nonstationary quantum states. In particular we discuss the
stationary states of quantum systems with singular velocity fields. We
introduce a technique that allows to realize arbitrary evolutions ruled by
these equations, to account for controlled quantum transitions. The method is
illustrated by presenting the detailed treatment of the transition
probabilities and of the controlling time-dependent potentials associated to
the transitions between the stationary, the coherent, and the squeezed states
of the harmonic oscillator. Possible extensions to anharmonic systems and mixed
states are briefly discussed and assessed.Comment: 24 pages, 4 figure
Light Microscopy Measurements of Ice Recrystallization in Frozen Corn Starch Pastes Using Isothermal Freeze Fixation
Isothermal freeze fixation was used to analyze ice recrystallization by light microscopy in a 10 % (W/W) frozen corn starch paste during storage at temperatures in the range of -5 to -20 °C.
Different formulations were tested in order to obtain a suitable fixative for this method of indirect observation of the ice crystals. A solution of formaldehyde, ethanol and water (10:45:45 V:V) was selected because it minimized substitution-induced distortion and contraction of the matrix. The diffusion coefficients of the selected fixative in the frozen system were measured at different temperatures in conditions of unidirectional mass transfer in a semi - infinite medium. The activation energy for diffusion was determined (Ea = 95.11 ± I. 15 KJ/mol).
Fixation times for the frozen starch paste at different temperatures were predicted from a mathematical model for unidirectional mass transfer with a discontinuous diffusion coefficient. Matrix contraction during the different stages of the freeze fixation method was evaluated.
Recrystallization of ice in frozen corn starch pastes during storage was analyzed by the measurement of the changes in ice crystal equivalent diameters on the micrographs. A kinetic equation for recrystallization was fitted to the experimental data to obtain the corresponding parameters. Contraction of the matrix affects the kinetic constants but has no effect on activation energy. The effect of recrystallization during fixation on ice crystal measurements was not significant
Broad-band characteristics of seven new hard X-ray selected cataclysmic variables
Indexación: Web of Science; Scopus.We present timing and spectral analysis of a sample of seven hard X-ray selected cataclysmic
variable candidates based on simultaneous X-ray and optical observations collected
with XMM–Newton, complemented with Swift/BAT and INTEGRAL /IBIS hard X-ray data
and ground-based optical photometry. For six sources, X-ray pulsations are detected for the
first time in the range of ∼296–6098 s, identifying them as members of the magnetic class.
Swift J0927.7−6945, Swift J0958.0−4208, Swift J1701.3−4304, Swift J2113.5+5422 and
possibly PBC J0801.2−4625 are intermediate polars (IPs), while Swift J0706.8+0325 is a
short (1.7 h) orbital period polar, the 11th hard X-ray-selected identified so far. X-ray orbital
modulation is also observed in Swift J0927.7−6945 (5.2 h) and Swift J2113.5+5422
(4.1 h). Swift J1701.3−4304 is discovered as the longest orbital period (12.8 h) deep eclipsing
IP. The spectra of the magnetic systems reveal optically thin multitemperature emission
between 0.2 and 60 keV. Energy-dependent spin pulses and the orbital modulation in
Swift J0927.7−6945 and Swift J2113.5+5422 are due to intervening local high-density absorbing
material (NH ∼ 1022 − 23 cm−2). In Swift J0958.0−4208 and Swift J1701.3−4304, a
soft X-ray blackbody (kT ∼ 50 and ∼80 eV) is detected, adding them to the growing group
of ‘soft’ IPs. White dwarf masses are determined in the range of ∼0.58–1.18 M, indicating
massive accreting primaries in five of them. Most sources accrete at rates lower than the
expected secular value for their orbital period. Formerly proposed as a long-period (9.4 h)
nova-like CV, Swift J0746.3−1608 shows peculiar spectrum and light curves suggesting either
an atypical low-luminosity CV or a low-mass X-ray binary.https://academic.oup.com/mnras/article/470/4/4815/390658
Fluctuation relations and rare realizations of transport observables
Fluctuation relations establish rigorous identities for the nonequilibrium
averages of observables. Starting from a general transport master equation with
time-dependent rates, we employ the stochastic path integral approach to study
statistical fluctuations around such averages. We show how under nonequilibrium
conditions, rare realizations of transport observables are crucial and imply
massive fluctuations that may completely mask such identities. Quantitative
estimates for these fluctuations are provided. We illustrate our results on the
paradigmatic example of a mesoscopic RC circuit.Comment: 4 pages, 3 figures; v2: minor changes, published versio
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