1,245 research outputs found
A classical analog to topological non-local quantum interference effect
The two main features of the Aharonov-Bohm effect are the topological
dependence of accumulated phase on the winding number around the magnetic
fluxon, and non-locality -- local observations at any intermediate point along
the trajectories are not affected by the fluxon. The latter property is usually
regarded as exclusive to quantum mechanics. Here we show that both the
topological and non-local features of the Aharonov-Bohm effect can be
manifested in a classical model that incorporates random noise. The model also
suggests new types of multi-particle topological non-local effects which have
no quantum analog.Comment: 4 pages, to be published in Phys. Rev. Let
Species Doublers as Super Multiplets in Lattice Supersymmetry: Exact Supersymmetry with Interactions for D=1 N=2
We propose a new lattice superfield formalism in momentum representation
which accommodates species doublers of the lattice fermions and their bosonic
counterparts as super multiplets. We explicitly show that one dimensional N=2
model with interactions has exact Lie algebraic supersymmetry on the lattice
for all super charges. In coordinate representation the finite difference
operator is made to satisfy Leibnitz rule by introducing a non local product,
the ``star'' product, and the exact lattice supersymmetry is realized. The
standard momentum conservation is replaced on the lattice by the conservation
of the sine of the momentum, which plays a crucial role in the formulation.
Half lattice spacing structure is essential for the one dimensional model and
the lattice supersymmetry transformation can be identified as a half lattice
spacing translation combined with alternating sign structure. Invariance under
finite translations and locality in the continuum limit are explicitly
investigated and shown to be recovered. Supersymmetric Ward identities are
shown to be satisfied at one loop level. Lie algebraic lattice supersymmetry
algebra of this model suggests a close connection with Hopf algebraic exactness
of the link approach formulation of lattice supersymmetry.Comment: 34 pages, 2 figure
Massless Decoupled Doublers: Chiral Yukawa Models and Chiral Gauge Theories
We present a new method for regularizing chiral theories on the lattice. The
arbitrariness in the regularization is used in order to decouple massless
replica fermions. A continuum limit with only one fermion is obtained in
perturbation theory and a Golterman-Petcher like symmetry related to the
decoupling of the replicas in the non-perturbative regime is identified. In the
case of Chiral Gauge Theories gauge invariance is broken at the level of the
regularization, so our approach shares many of the characteristics of the Rome
approach.Comment: 11 page
Dephasing in sequential tunneling through a double-dot interferometer
We analyze dephasing in a model system where electrons tunnel sequentially
through a symmetric interference setup consisting of two single-level quantum
dots. Depending on the phase difference between the two tunneling paths, this
may result in perfect destructive interference. However, if the dots are
coupled to a bath, it may act as a which-way detector, leading to partial
suppression of the phase-coherence and the reappearance of a finite tunneling
current. In our approach, the tunneling is treated in leading order whereas
coupling to the bath is kept to all orders (using P(E) theory). We discuss the
influence of different bath spectra on the visibility of the interference
pattern, including the distinction between "mere renormalization effects" and
"true dephasing".Comment: 18 pages, 8 figures; For a tutorial introduction to dephasing see
http://iff.physik.unibas.ch/~florian/dephasing/dephasing.htm
Vortex waistlines and long range fluctuations
We examine the manner in which a linear potential results from fluctuations
due to vortices linked with the Wilson loop. Our discussion is based on exact
relations and inequalities between the Wilson loop and the vortex and electric
flux order parameters. We show that, contrary to the customary naive picture,
only vortex fluctuations of thickness of the order of the spatial linear size
of the loop are capable of producing a strictly linear potential. An effective
theory of these long range fluctuations emerges naturally in the form of a
strongly coupled Z(N) lattice gauge theory. We also point out that dynamical
fermions introduced in this medium undergo chiral symmetry breaking.Comment: 17 pages, LaTex file with 7 eps figures, revised references, minor
comments adde
Dirac-like Monopoles in Three Dimensions and Their Possible Influences on the Dynamics of Particles
Dirac-like monopoles are studied in three-dimensional Abelian Maxwell and
Maxwell-Chern-Simons models. Their scalar nature is highlighted and discussed
through a dimensional reduction of four-dimensional electrodynamics with
electric and magnetic sources. Some general properties and similarities of them
when are considered in Minkowski or Euclidian space are mentioned. However, by
virtue of the structure of the space-time in which they are considered a number
of differences among them take place. Furthermore, we pay attention to some
consequences of these objects when acting upon usual particles. Among other
subjects, special attention is given to the study of a Lorentz-violating
non-minimal coupling between neutral fermions and the field generated by a
monopole alone. In addition, an analogue of the Aharonov-Casher effect is
discussed in this framework.Comment: 20 pages. Latex format. No figures. Accepted for publication in Phys.
Rev.
Colossal barocaloric effects near room temperature in plastic crystals of neopentylglycol.
There is currently great interest in replacing the harmful volatile hydrofluorocarbon fluids used in refrigeration and air-conditioning with solid materials that display magnetocaloric, electrocaloric or mechanocaloric effects. However, the field-driven thermal changes in all of these caloric materials fall short with respect to their fluid counterparts. Here we show that plastic crystals of neopentylglycol (CH3)2C(CH2OH)2 display extremely large pressure-driven thermal changes near room temperature due to molecular reconfiguration, that these changes outperform those observed in any type of caloric material, and that these changes are comparable with those exploited commercially in hydrofluorocarbons. Our discovery of colossal barocaloric effects in a plastic crystal should bring barocaloric materials to the forefront of research and development in order to achieve safe environmentally friendly cooling without compromising performance
Anti-nausea effects and pharmacokinetics of ondansetron, maropitant and metoclopramide in a low-dose cisplatin model of nausea and vomiting in the dog: a blinded crossover study
Nausea is a subjective sensation which is difficult to measure in non-verbal species. The aims of this study were to determine the efficacy of three classes of antiemetic drugs in a novel low dose cisplatin model of nausea and vomiting and measure change in potential nausea biomarkers arginine vasopressin (AVP) and cortisol. A four period cross-over blinded study was conducted in eight healthy beagle dogs of both genders. Dogs were administered 18 mg/m2 cisplatin intravenously, followed 45 min later by a 15 min infusion of either placebo (saline) or antiemetic treatment with ondansetron (0.5 mg/kg; 5-HT3 antagonist), maropitant (1 mg/kg; NK1 antagonist) or metoclopramide (0.5 mg/kg; D2 antagonist). The number of vomits and nausea associated behaviours, scored on a visual analogue scale, were recorded every 15 min for 8 h following cisplatin administration. Plasma samples were collected to measure AVP, cortisol and antiemetic drug concentrations
Dynamical Wilson fermions and the problem of the chiral limit in compact lattice QED
We compare the approach to the chiral transition line ~\kappa_c(\bt)~ in
quenched and full compact lattice QED with Wilson fermions within the
confinement phase, especially in the pseudoscalar sector of the theory. We show
that in the strong coupling limit () the quenched theory is a good
approximation to the full one, in contrast to the case of . At the
larger -value the transition in the full theory is inconsistent with the
zero--mass limit of the pseudoscalar particle, thus prohibiting the definition
of a chiral limit.Comment: 13 pages LaTeX (epsf), all figures include
Numerical properties of staggered quarks with a taste-dependent mass term
The numerical properties of staggered Dirac operators with a taste-dependent
mass term proposed by Adams [1,2] and by Hoelbling [3] are compared with those
of ordinary staggered and Wilson Dirac operators. In the free limit and on
(quenched) interacting configurations, we consider their topological
properties, their spectrum, and the resulting pion mass. Although we also
consider the spectral structure, topological properties, locality, and
computational cost of an overlap operator with a staggered kernel, we call
attention to the possibility of using the Adams and Hoelbling operators without
the overlap construction. In particular, the Hoelbling operator could be used
to simulate two degenerate flavors without additive mass renormalization, and
thus without fine-tuning in the chiral limit.Comment: 14 pages, 9 figures. V2: published version; important note added
regarding Hoelbling fermions, otherwise minor change
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