5,121 research outputs found
Conformal Symmetry on the Instanton Moduli Space
The conformal symmetry on the instanton moduli space is discussed using the
ADHM construction, where a viewpoint of "homogeneous coordinates" for both the
spacetime and the moduli space turns out to be useful. It is shown that the
conformal algebra closes only up to global gauge transformations, which
generalizes the earlier discussion by Jackiw et al. An interesting
5-dimensional interpretation of the SU(2) single-instanton is also mentioned.Comment: 7 pages, LaTeX, version to appear in J. Phys. A: Math. Ge
Weakly Equivalent Arrays
The (extensional) theory of arrays is widely used to model systems. Hence,
efficient decision procedures are needed to model check such systems. Current
decision procedures for the theory of arrays saturate the read-over-write and
extensionality axioms originally proposed by McCarthy. Various filters are used
to limit the number of axiom instantiations while preserving completeness. We
present an algorithm that lazily instantiates lemmas based on weak equivalence
classes. These lemmas are easier to interpolate as they only contain existing
terms. We formally define weak equivalence and show correctness of the
resulting decision procedure
Unexpected Spin-Off from Quantum Gravity
We propose a novel way of investigating the universal properties of spin
systems by coupling them to an ensemble of causal dynamically triangulated
lattices, instead of studying them on a fixed regular or random lattice.
Somewhat surprisingly, graph-counting methods to extract high- or
low-temperature series expansions can be adapted to this case. For the
two-dimensional Ising model, we present evidence that this ameliorates the
singularity structure of thermodynamic functions in the complex plane, and
improves the convergence of the power series.Comment: 10 pages, 4 figures; final, slightly amended version, to appear in
Physica
Social organization of authenticity in Mexican restaurants
This dissertation analyzes the social worlds of the Mexican restaurant industry. First, the topic of organizational constructions and presentations of authenticity is investigated. In examining the relation between discourses of business (profit) and aesthetics (authenticity) in Mexican restaurant contexts in which authenticity is a major theme, this study demonstrates the processes of negotiation and policing which form the "authentic" experience for patrons of restaurants. The second major theme explored in this dissertation is the subjective dimension of authenticity among Mexican immigrant men working in the Mexican restaurant industry. Traditionally marked as women's work, restaurant food preparation and serving is almost exclusively a male dominated niche of the labor force. Based on data gathered in the field, this project introduces the concept of gender posturing and homosocial behaviors as a means of developing a pragmatic understanding of the many ways male restaurant workers define, perform, negotiate, and police the boundaries of acceptable forms of masculinity. The third major theme of this project blends discussions of organizational and subjective dimensions of authenticity as it explores the basis and negative impacts of stereotypes on ethnic restaurant profitability. An examination of the institutional bias ethnic restaurant owners and workers perceive and experience during regular county health inspections demonstrates the influence of public discourse on the marking of ethnic restaurants
Effective Quantum Dynamics of Interacting Systems with Inhomogeneous Coupling
We study the quantum dynamics of a single mode/particle interacting
inhomogeneously with a large number of particles and introduce an effective
approach to find the accessible Hilbert space where the dynamics takes place.
Two relevant examples are given: the inhomogeneous Tavis-Cummings model (e.g.,
N atomic qubits coupled to a single cavity mode, or to a motional mode in
trapped ions) and the inhomogeneous coupling of an electron spin to N nuclear
spins in a quantum dot.Comment: 9 pages and 10 figures, new version, accepted in Physical Review
Method for reducing sidelobe impact of low order aberration in a coronagraph
The invention relates to a method for reducing a sidelobe impact of low order aberrations using a coronagraph (2) having an apodized occulting mask (10), comprising the steps of: (a) providing in the coronagraph (2) the apodized occulting disk (10) having a transmission profile which graduates from opaque to transparent along its radius and the negative of whose amplitude transmission is a Gaussian profile; (b) determining a predicted sidelobe impact of the aberrations from a particular mix of low order aberration measured in a system as described by the Zernike polynomials; (c) applying the coronagraph to a system point spread function using a given rms width for the Gaussian profile describing the apodized occulting mask (10) and determining an attenuation level of the aberration sidelobes; (d) scaling the Gaussian occulting mask (10) profile to a wider rms width if the sidelobe attenuation level is too low; and (e) repeating the steps (b) through (d) until the attenuation level is acceptable
From quantum pulse gate to quantum pulse shaper -- enigneered frequency conversion in nonlinear optical waveguides
Full control over the spatio-temporal structure of quantum states of light is
an important goal in quantum optics, to generate for instance single-mode
quantum pulses or to encode information on multiple modes, enhancing channel
capacities. Quantum light pulses feature an inherent, rich spectral
broadband-mode structure. In recent years, exploring the use of integrated
optics as well as source-engineering has led to a deep understanding of the
pulse-mode structure of guided quantum states of light. In addition, several
groups have started to investigate the manipulation of quantum states by means
of single-photon frequency conversion. In this paper we explore new routes
towards complete control of the inherent pulse-modes of ultrafast pulsed
quantum states by employing specifically designed nonlinear waveguides with
adapted dispersion properties. Starting from our recently proposed quantum
pulse gate (QPG) we further generalize the concept of spatio-spectral
engineering for arbitrary \chitwo-based quantum processes. We analyse the
sum-frequency generation based QPG and introduce the difference-frequency
generation based quantum pulse shaper (QPS). Together, these versatile and
robust integrated optics devices allow for arbitrary manipulations of the
pulse-mode structure of ultrafast pulsed quantum states. The QPG can be
utilized to select an arbitrary pulse mode from a multimode input state,
whereas the QPS enables the generation of specific pulse modes from an input
wavepacket with Gaussian-shaped spectrum.Comment: 21 pages, 9 figure
Shaken, but not stirred - Potts model coupled to quantum gravity
We investigate the critical behaviour of both matter and geometry of the
three-state Potts model coupled to two-dimensional Lorentzian quantum gravity
in the framework of causal dynamical triangulations. Contrary to what general
arguments of the effects of disorder suggest, we find strong numerical evidence
that the critical exponents of the matter are not changed under the influence
of quantum fluctuations in the geometry, compared to their values on fixed,
regular lattices. This lends further support to previous findings that quantum
gravity models based on causal dynamical triangulations are in many ways better
behaved than their Euclidean counterparts.Comment: 19 pages, 9 figure
kalis: a modern implementation of the Li & Stephens model for local ancestry inference in R
Background: Approximating the recent phylogeny of N phased haplotypes at a set of variants along the genome is a core problem in modern population genomics and central to performing genome-wide screens for association, selection, introgression, and other signals. The Li & Stephens (LS) model provides a simple yet powerful hidden Markov model for inferring the recent ancestry at a given variant, represented as an N×N distance matrix based on posterior decodings. Results: We provide a high-performance engine to make these posterior decodings readily accessible with minimal pre-processing via an easy to use package kalis, in the statistical programming language R. kalis enables investigators to rapidly resolve the ancestry at loci of interest and developers to build a range of variant-specific ancestral inference pipelines on top. kalis exploits both multi-core parallelism and modern CPU vector instruction sets to enable scaling to hundreds of thousands of genomes. Conclusions: The resulting distance matrices accessible via kalis enable local ancestry, selection, and association studies in modern large scale genomic datasets
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