928 research outputs found
Topological Wilson-loop area law manifested using a superposition of loops
We introduce a new topological effect involving interference of two meson
loops, manifesting a path-independent topological area dependence. The effect
also draws a connection between quark confinement, Wilson-loops and topological
interference effects. Although this is only a gedanken experiment in the
context of particle physics, such an experiment may be realized and used as a
tool to test confinement effects and phase transitions in quantum simulation of
dynamic gauge theories.Comment: Superceding arXiv:1206.2021v1 [quant-ph
The Fermi Problem in Discrete Systems
The Fermi two-atom problem illustrates an apparent causality violation in
Quantum Field Theory which has to do with the nature of the built in
correlations in the vacuum. It has been a constant subject of theoretical
debate and discussions during the last few decades. Nevertheless, although the
issues at hand could in principle be tested experimentally, the smallness of
such apparent violations of causality in Quantum Electrodynamics prevented the
observation of the predicted effect. In the present paper we show that the
problem can be simulated within the framework of discrete systems that can be
manifested, for instance, by trapped atoms in optical lattices or trapped ions.
Unlike the original continuum case, the causal structure is no longer sharp.
Nevertheless, as we show, it is possible to distinguish between "trivial"
effects due to "direct" causality violations, and the effects associated with
Fermi's problem, even in such discrete settings. The ability to control
externally the strength of the atom-field interactions, enables us also to
study both the original Fermi problem with "bare atoms", as well as correction
in the scenario that involves "dressed" atoms. Finally, we show that in
principle, the Fermi effect can be detected using trapped ions.Comment: Second version - minor change
Goal-conflict detection based on temporal satisfiability checking
Goal-oriented requirements engineering approaches propose capturing how a system should behave through the speci ca- tion of high-level goals, from which requirements can then be systematically derived. Goals may however admit subtle situations that make them diverge, i.e., not be satis able as a whole under speci c circumstances feasible within the domain, called boundary conditions . While previous work al- lows one to identify boundary conditions for con icting goals written in LTL, it does so through a pattern-based approach, that supports a limited set of patterns, and only produces pre-determined formulations of boundary conditions. We present a novel automated approach to compute bound- ary conditions for general classes of con icting goals expressed in LTL, using a tableaux-based LTL satis ability procedure. A tableau for an LTL formula is a nite representation of all its satisfying models, which we process to produce boundary conditions that violate the formula, indicating divergence situations. We show that our technique can automatically produce boundary conditions that are more general than those obtainable through existing previous pattern-based approaches, and can also generate boundary conditions for goals that are not captured by these patterns
Generalized Elitzur's Theorem and Dimensional Reduction
We extend Elitzur's theorem to systems with symmetries intermediate between
global and local. In general, our theorem formalizes the idea of {\it
dimensional reduction}. We apply the results of this generalization to many
systems that are of current interest. These include liquid crystalline phases
of Quantum Hall systems, orbital systems, geometrically frustrated spin
lattices, Bose metals, and models of superconducting arrays.Comment: 10 pages, 1 figur
Spin and Spin-Wave Dynamics in Josephson Junctions
We extend the Keldysh formulation to quantum spin systems and derive exact
equations of motion. This allows us to explore the dynamics of single spins and
of ferromagnets when these are inserted between superconducting leads. Several
new effects are reported. Chief amongst these are nutations of single S=1/2
spins in Josephson junctions. These nutations are triggered by the
superconducting pairing correlations in the leads. Similarly, we find that on
rather universal grounds, magnets display unconventional spin wave dynamics
when placed in Josephson junctions. These lead to modifications in the
tunneling current.Comment: (14 pages, 5 figures
A Bound on the Superpotential
We prove a general bound on the superpotential in theories with broken
supersymmetry and broken R-symmetry, 2|W|< f_a F, where f_a and F are the
R-axion and Goldstino decay constants, respectively. The bound holds for weakly
coupled as well as strongly coupled theories, thereby providing an exact result
in theories with broken supersymmetry. We briefly discuss several possible
applications.Comment: 20 page
Strontium and Oxygen Isotope Analyses Reveal Late Cretaceous Shark Teeth in Iron Age Strata in the Southern Levant
Skeletal remains in archaeological strata are often assumed to be of similar ages. Here we show that combined Sr and O isotope analyses can serve as a powerful tool for assessing fish provenance and even for identifying fossil fish teeth in archaeological contexts. For this purpose, we established a reference Sr and O isotope dataset of extant fish teeth from major water bodies in the Southern Levant. Fossil shark teeth were identified within Iron Age cultural layers dating to 8â9th century BCE in the City of David, Jerusalem, although the reason for their presence remains unclear. Their enameloid 87Sr/86Sr and ÎŽ18OPO4 values [0.7075 ± 0.0001 (1 SD, n = 7) and 19.6 ± 0.9â° (1 SD, n = 6), respectively], are both much lower than values typical for modern marine sharks from the Mediterranean Sea [0.7092 and 22.5â24.6â° (n = 2), respectively]. The sharksâ 87Sr/86Sr are also lower than those of rain- and groundwater as well as the main soil types in central Israel (â„0.7079). This indicates that these fossil sharks incorporated Sr (87Sr/86Sr â 0.7075) from a marine habitat with values typical for Late Cretaceous seawater. This scenario is in line with the low shark enameloid ÎŽ18OPO4 values reflecting tooth formation in the warm tropical seawater of the Tethys Ocean. Age estimates using 87Sr/86Sr stratigraphy place these fossil shark teeth at around 80-million-years-old. This was further supported by their taxonomy and the high dentine apatite crystallinity, low organic carbon, high U and Nd contents, characteristics that are typical for fossil specimens, and different from those of archaeological Gilthead seabream (Sparus aurata) teeth from the same cultural layers and another Chalcolithic site (Gilat). Chalcolithic and Iron Age seabream enameloid has seawater-like 87Sr/86Sr of 0.7091 ± 0.0001 (1 SD, n = 6), as expected for modern marine fish. Fossil shark and archaeological Gilthead seabream teeth both preserve original, distinct enameloid 87Sr/86Sr and ÎŽ18OPO4 signatures reflecting their different aquatic habitats. Fifty percent of the analysed Gilthead seabream teeth derive from hypersaline seawater, indicating that these seabreams were exported from the hypersaline Bardawil Lagoon in Sinai (Egypt) to the Southern Levant since the Iron Age period and possibly even earlier
Lifetime Bipolar Disorder comorbidity and related clinical characteristics in patients with primary Obsessive Compulsive Disorder: a report from the International College of Obsessive-Compulsive Spectrum Disorders (ICOCS)
IntroductionBipolar disorder (BD) and obsessive compulsive disorder (OCD) are prevalent, comorbid, and disabling conditions, often characterized by early onset and chronic course. When comorbid, OCD and BD can determine a more pernicious course of illness, posing therapeutic challenges for clinicians. Available reports on prevalence and clinical characteristics of comorbidity between BD and OCD showed mixed results, likely depending on the primary diagnosis of analyzed samples.MethodsWe assessed prevalence and clinical characteristics of BD comorbidity in a large international sample of patients with primary OCD (n = 401), through the International College of Obsessive-Compulsive Spectrum Disorders (ICOCS) snapshot database, by comparing OCD subjects with vs without BD comorbidity.ResultsAmong primary OCD patients, 6.2% showed comorbidity with BD. OCD patients with vs without BD comorbidity more frequently had a previous hospitalization (p < 0.001) and current augmentation therapies (p < 0.001). They also showed greater severity of OCD (p < 0.001), as measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS).ConclusionThese findings from a large international sample indicate that approximately 1 out of 16 patients with primary OCD may additionally have BD comorbidity along with other specific clinical characteristics, including more frequent previous hospitalizations, more complex therapeutic regimens, and a greater severity of OCD. Prospective international studies are needed to confirm our findings.Peer reviewe
The Constraints of Conformal Symmetry on RG Flows
If the coupling constants in QFT are promoted to functions of space-time, the
dependence of the path integral on these couplings is highly constrained by
conformal symmetry. We begin the present note by showing that this idea leads
to a new proof of Zamolodchikov's theorem. We then review how this simple
observation also leads to a derivation of the a-theorem. We exemplify the
general procedure in some interacting theories in four space-time dimensions.
We concentrate on Banks-Zaks and weakly relevant flows, which can be controlled
by ordinary and conformal perturbation theories, respectively. We compute
explicitly the dependence of the path integral on the coupling constants and
extract the change in the a-anomaly (this agrees with more conventional
computations of the same quantity). We also discuss some general properties of
the sum rule found in arXiv:1107.3987 and study it in several examples.Comment: 25 pages, 5 figure
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