38 research outputs found
Correlation inequalities for classical and quantum XY models
We review correlation inequalities of truncated functions for the classical
and quantum XY models. A consequence is that the critical temperature of the XY
model is necessarily smaller than that of the Ising model, in both the
classical and quantum cases. We also discuss an explicit lower bound on the
critical temperature of the quantum XY model.Comment: 13 pages. Submitted to the volume "Advances in Quantum Mechanics:
contemporary trends and open problems" of the INdAM-Springer series,
proceedings of the INdAM meeting "Contemporary Trends in the Mathematics of
Quantum Mechanics" (4-8 July 2016) organised by G. Dell'Antonio and A.
Michelangel
Homodyne Bell's inequalities for entangled mesoscopic superpositions
We present a scheme for demonstrating violation of Bell's inequalities using
a spin-1/2 system entangled with a pair of classically distinguishable wave
packets in a harmonic potential. In the optical domain, such wave packets can
be represented by coherent states of a single light mode. The proposed scheme
involves standard spin-1/2 projections and measurements of the position and the
momentum of the harmonic oscillator system, which for a light mode can be
realized by means of homodyne detection. We discuss effects of imperfections,
including non-unit efficiency of the homodyne detector, and point out a close
link between the visibility of interference and violation of Bell's
inequalities in the described scheme.Comment: 6 pages, 3 figures. Extended version, journal reference adde
Potts model on recursive lattices: some new exact results
We compute the partition function of the Potts model with arbitrary values of
and temperature on some strip lattices. We consider strips of width
, for three different lattices: square, diced and `shortest-path' (to be
defined in the text). We also get the exact solution for strips of the Kagome
lattice for widths . As further examples we consider two lattices
with different type of regular symmetry: a strip with alternating layers of
width and , and a strip with variable width. Finally we make
some remarks on the Fisher zeros for the Kagome lattice and their large
q-limit.Comment: 17 pages, 19 figures. v2 typos corrected, title changed and
references, acknowledgements and two further original examples added. v3 one
further example added. v4 final versio
Cowries in the archaeology of West Africa: the present picture
Despite the perceived importance of cowrie shells as indicators of long-distance connections in the West African past, their distribution and consumption patterns in archaeological contexts remain surprisingly underexplored, a gap that is only partly explicable by the sparse distribution of archaeological sites within the sub-continent. General writings on the timeline of importation of cowries into West Africa often fail to take into account the latest archaeological evidence and rely instead on accounts drawn from historical or ethnographic documents. This paper is based on a first-hand assessment of over 4500 shells from 78 sites across West Africa, examining chronology, shell species and processes of modification to assess what distribution patterns can tell us about the history of importation and usage of cowries. These first-hand analyses are paralleled by a consideration of published materials. We re-examine the default assumption that two distinct routes of entry existed â one overland from North Africa before the fifteenth century, another coming into use from the time sea links were established with the East African coast and becoming predominant by the middle of the nineteenth century. We focus on the eastern part of West Africa, where the importance of imported cowries to local communities in relatively recent periods is well known and from where we have a good archaeological sample. The conclusion is that on suitably large assemblages shell size can be an indication of provenance and that, while the present archaeological picture seems largely to confirm historical sources, much of this may be due to the discrepancy in archaeological data available from the Sahara/Sahel zone compared to the more forested regions of the sub-continent. Future archaeological work will clarify this matter
The WEBT BL Lacertae Campaign 2001 and its extension : Optical light curves and colour analysis 1994â2002
BL Lacertae has been the target of four observing campaigns by the Whole Earth Blazar Telescope (WEBT) collaboration. In this paper we present UBVRI light curves obtained by theWEBT from 1994 to 2002, including the last, extended BL Lac 2001 campaign. A total of about 7500 optical observations performed by 31 telescopes from Japan to Mexico have been collected, to be added to the âŒ15 600 observations of the BL Lac Campaign 2000. All these data allow one to follow the source optical emission behaviour with unprecedented detail. The analysis of the colour indices reveals that the flux variability can be interpreted in terms of two components: longer-term variations occurring on a fewday time scale appear as mildly-chromatic events, while a strong bluer-when-brighter chromatism characterizes very fast (intraday) flares. By decoupling the two components, we quantify the degree of chromatism inferring that longer-term flux changes imply moving along a âŒ0.1 bluerwhen- brighter slope in the B â R versus R plane; a steeper slope of âŒ0.4 would distinguish the shorter-term variations. This means that, when considering the long-term trend, the B-band flux level is related to the R-band one according to a power law of index âŒ1.1. Doppler factor variations on a âconvexâ spectrum could be the mechanism accounting for both the long-term variations and their slight chromatism.Reig Torres, Pablo, [email protected]
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Track A Basic Science
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138319/1/jia218438.pd
Equivalence between macroscopic quantum superpositions and maximally entangled states: Application to phase-shift detection
Multi-ancestry GWAS of the electrocardiographic PR interval identifies 202 loci underlying cardiac conduction
The electrocardiographic PR interval reflects atrioventricular conduction, and is associated with conduction abnormalities, pacemaker implantation, atrial fibrillation (AF), and cardiovascular mortality. Here we report a multi-ancestry (N = 293,051) genome-wide association meta-analysis for the PR interval, discovering 202 loci of which 141 have not previously been reported. Variants at identified loci increase the percentage of heritability explained, from 33.5% to 62.6%. We observe enrichment for cardiac muscle developmental/contractile and cytoskeletal genes, highlighting key regulation processes for atrioventricular conduction. Additionally, 8 loci not previously reported harbor genes underlying inherited arrhythmic syndromes and/or cardiomyopathies suggesting a role for these genes in cardiovascular pathology in the general population. We show that polygenic predisposition to PR interval duration is an endophenotype for cardiovascular disease, including distal conduction disease, AF, and atrioventricular pre-excitation. These findings advance our understanding of the polygenic basis of cardiac conduction, and the genetic relationship between PR interval duration and cardiovascular disease