2,877 research outputs found
Experience Implementing a Performant Category-Theory Library in Coq
We describe our experience implementing a broad category-theory library in
Coq. Category theory and computational performance are not usually mentioned in
the same breath, but we have needed substantial engineering effort to teach Coq
to cope with large categorical constructions without slowing proof script
processing unacceptably. In this paper, we share the lessons we have learned
about how to represent very abstract mathematical objects and arguments in Coq
and how future proof assistants might be designed to better support such
reasoning. One particular encoding trick to which we draw attention allows
category-theoretic arguments involving duality to be internalized in Coq's
logic with definitional equality. Ours may be the largest Coq development to
date that uses the relatively new Coq version developed by homotopy type
theorists, and we reflect on which new features were especially helpful.Comment: The final publication will be available at link.springer.com. This
version includes a full bibliography which does not fit in the Springer
version; other than the more complete references, this is the version
submitted as a final copy to ITP 201
Cosmological and Astrophysical Neutrino Mass Measurements
Cosmological and astrophysical measurements provide powerful constraints on
neutrino masses complementary to those from accelerators and reactors. Here we
provide a guide to these different probes, for each explaining its physical
basis, underlying assumptions, current and future reach.Comment: 11 page
Quantum computing of quantum chaos and imperfection effects
We study numerically the imperfection effects in the quantum computing of the
kicked rotator model in the regime of quantum chaos. It is shown that there are
two types of physical characteristics: for one of them the quantum computation
errors grow exponentially with the number of qubits in the computer while for
the other the growth is polynomial. Certain similarity between classical and
quantum computing errors is also discussed.Comment: revtex, 4 pages, 4 figure
Dissipative effects on quantum glassy systems
We discuss the behavior of a quantum glassy system coupled to a bath of
quantum oscillators. We show that the system localizes in the absence of
interactions when coupled to a subOhmic bath. When interactions are switched on
localization disappears and the system undergoes a phase transition towards a
glassy phase. We show that the position of the critical line separating the
disordered and the ordered phases strongly depends on the coupling to the bath.
For a given type of bath, the ordered glassy phase is favored by a stronger
coupling. Ohmic, subOhmic and superOhmic baths lead to different transition
lines. We draw our conclusions from the analysis of the partition function
using the replicated imaginary-time formalism and from the study of the
real-time dynamics of the coupled system using the Schwinger-Keldysh closed
time-path formalism.Comment: 39 pages, 13 figures, RevTe
Precision Physics at LEP
1 - Introduction
2 - Small-Angle Bhabha Scattering and the Luminosity Measurement
3 - Z^0 Physics
4 - Fits to Precision Data
5 - Physics at LEP2
6 - ConclusionsComment: Review paper to appear in the RIVISTA DEL NUOVO CIMENTO; 160 pages,
LateX, 70 eps figures include
Event Generators for WW Physics
The report summarizes the results of the activities of the Working Group on
Event Generators for WW Physics at CERN during 1995.Comment: 99 Latex, including 30 figures, 24 tables. The report is part of:
G.Altarelli,T.Sjostrand and F.Zwirner (eds), Physics at LEP2 CERN 96-0
Quantum computing and information extraction for a dynamical quantum system
We discuss the simulation of a complex dynamical system, the so-called
quantum sawtooth map model, on a quantum computer. We show that a quantum
computer can be used to efficiently extract relevant physical information for
this model. It is possible to simulate the dynamical localization of classical
chaos and extract the localization length of the system with quadratic speed up
with respect to any known classical computation. We can also compute with
algebraic speed up the diffusion coefficient and the diffusion exponent both in
the regimes of Brownian and anomalous diffusion. Finally, we show that it is
possible to extract the fidelity of the quantum motion, which measures the
stability of the system under perturbations, with exponential speed up.Comment: 11 pages, 5 figures, submitted to Quantum Information Processing,
Special Issue devoted to the Physics of Quantum Computin
Existential witness extraction in classical realizability and via a negative translation
We show how to extract existential witnesses from classical proofs using
Krivine's classical realizability---where classical proofs are interpreted as
lambda-terms with the call/cc control operator. We first recall the basic
framework of classical realizability (in classical second-order arithmetic) and
show how to extend it with primitive numerals for faster computations. Then we
show how to perform witness extraction in this framework, by discussing several
techniques depending on the shape of the existential formula. In particular, we
show that in the Sigma01-case, Krivine's witness extraction method reduces to
Friedman's through a well-suited negative translation to intuitionistic
second-order arithmetic. Finally we discuss the advantages of using call/cc
rather than a negative translation, especially from the point of view of an
implementation.Comment: 52 pages. Accepted in Logical Methods for Computer Science (LMCS),
201
Superspace formulations of the (super)twistor string
The superspace formulation of the worldvolume action of twistor string models
is considered. It is shown that for the Berkovits-Siegel closed twistor string
such a formulation is provided by a N=4 twistor-like action of the tensionless
superstring. A similar inverse twistor transform of the open twistor string
model (Berkovits model) results in a dynamical system containing two copies of
the D=4, N=4 superspace coordinate functions, one left-moving and one
right-moving, that are glued by the boundary conditions.
We also discuss possible candidates for a tensionful superstring action
leading to the twistor string in the tensionless limit as well as
multidimensional counterparts of twistor strings in the framework of both
`standard' superspace and superspace enlarged by tensorial coordinates
(tensorial superspaces), which constitute a natural framework for massless
higher spin theories.Comment: Rev Tex, 13 pages, no figure
Anti-nociceptive effect of Faecalibacterium prausnitzii in non-inflammatory IBS-like models
International audienceVisceral pain and intestinal dysbiosis are associated with Irritable Bowel Syndrome (IBS), a common functional gastrointestinal disorder without available efficient therapies. In this study, a decrease of Faecalibacterium prausnitzii presence has been observed in an IBS-like rodent model induced by a neonatal maternal separation (NMS) stress. Moreover, it was investigated whether F. prausnitzii may have an impact on colonic sensitivity. The A2-165 reference strain, but not its supernatant, significantly decreased colonic hypersensitivity induced by either NMS in mice or partial restraint stress in rats. This effect was associated with a reinforcement of intestinal epithelial barrier. Thus, F. prausnitzii exhibits anti-nociceptive properties, indicating its potential to treat abdominal pain in IBS patients
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