145 research outputs found
Affine holomorphic quantization
We present a rigorous and functorial quantization scheme for affine field
theories, i.e., field theories where local spaces of solutions are affine
spaces. The target framework for the quantization is the general boundary
formulation, allowing to implement manifest locality without the necessity for
metric or causal background structures. The quantization combines the
holomorphic version of geometric quantization for state spaces with the Feynman
path integral quantization for amplitudes. We also develop an adapted notion of
coherent states, discuss vacuum states, and consider observables and their
Berezin-Toeplitz quantization. Moreover, we derive a factorization identity for
the amplitude in the special case of a linear field theory modified by a
source-like term and comment on its use as a generating functional for a
generalized S-matrix.Comment: 42 pages, LaTeX + AMS; v2: expanded to improve readability, new
sections 3.1 (geometric data) and 3.3 (core axioms), minor corrections,
update of references; v3: further update of reference
Conceptual inconsistencies in finite-dimensional quantum and classical mechanics
Utilizing operational dynamic modeling [Phys. Rev. Lett. 109, 190403 (2012);
arXiv:1105.4014], we demonstrate that any finite-dimensional representation of
quantum and classical dynamics violates the Ehrenfest theorems. Other
peculiarities are also revealed, including the nonexistence of the free
particle and ambiguity in defining potential forces. Non-Hermitian mechanics is
shown to have the same problems. This work compromises a popular belief that
finite-dimensional mechanics is a straightforward discretization of the
corresponding infinite-dimensional formulation.Comment: 5 pages, 2 figure
Berry Phase Quantum Thermometer
We show how Berry phase can be used to construct an ultra-high precision
quantum thermometer. An important advantage of our scheme is that there is no
need for the thermometer to acquire thermal equilibrium with the sample. This
reduces measurement times and avoids precision limitations.Comment: Updated to published version. I. Fuentes previously published as I.
Fuentes-Guridi and I. Fuentes-Schulle
Semiclassical Analysis of the Wigner -Symbol with Small and Large Angular Momenta
We derive a new asymptotic formula for the Wigner -symbol, in the limit
of one small and eight large angular momenta, using a novel gauge-invariant
factorization for the asymptotic solution of a set of coupled wave equations.
Our factorization eliminates the geometric phases completely, using
gauge-invariant non-canonical coordinates, parallel transports of spinors, and
quantum rotation matrices. Our derivation generalizes to higher -symbols.
We display without proof some new asymptotic formulas for the -symbol and
the -symbol in the appendices. This work contributes a new asymptotic
formula of the Wigner -symbol to the quantum theory of angular momentum,
and serves as an example of a new general method for deriving asymptotic
formulas for -symbols.Comment: 18 pages, 16 figures. To appear in Phys. Rev.
States and amplitudes for finite regions in a two-dimensional Euclidean quantum field theory
We quantize the Helmholtz equation (plus perturbative interactions) in two
dimensions to illustrate a manifestly local description of quantum field
theory. Using the general boundary formulation we describe the quantum dynamics
both in a traditional time evolution setting as well as in a setting referring
to finite disk (or annulus) shaped regions of spacetime. We demonstrate that
both descriptions are equivalent when they should be.Comment: 19 pages, LaTeX + revtex4; minor correction
Lorentz and CPT Tests in Matter and Antimatter
A review of recent theoretical work investigating tests of Lorentz and CPT
symmetry in atomic and particle systems is presented. A variety of tests in
matter and antimatter are discussed, including measurements of anomalous
magnetic moments in Penning traps, comparisons of atomic-clock transitions,
high-precision spectroscopic measurements of hydrogen and antihydrogen,
experiments with muons, experiments with mesons, and tests of Lorentz symmetry
with a spin-polarized torsion pendulum.Comment: 8 pages. Talk presented at POSITRON 03, Sandbjerg, Denmark, July 200
Compliance of a cobalt chromium coronary stent alloy – the COVIS trial
BACKGROUND: Cobalt chromium coronary stents are increasingly being used in percutaneous coronary interventions. There are, however, no reliable data about the characteristics of unfolding and visibility of this stent alloy in vivo. The aim of this study is to compare cobalt chromium coronary stents with conventional stainless steel stents using intracoronary ultrasound. METHODS: Twenty de novo native coronary stenoses ≤ 20 mm in length (target vessel reference diameter ≥ 2.5 and ≤ 4.0 mm) received under sequential intracoronary ultrasound either a cobalt chromium stent (Multi-Link Vision(®); n = 10) or a stainless steel stent (Multi-Link Zeta(®); n = 10). RESULTS: For optimal unfolding, the cobalt chromium stent requires a higher balloon deployment pressure (13.90 ± 2.03 atm) than the stainless steel stent (11.50 ± 2.12 atm). Furthermore, the achieved target vessel diameter of the cobalt chromium stent (Visibility-Index QCA/IVUS Multi-Link Vision(®)1.13 / Multi-Link Zeta(® )1.04) is more easily overrated by Quantitative Coronary Analysis. CONCLUSION: These data indicate that stent material-specific recommendations for optimal implantation pressure and different stent material with an equal design should both be considered in interpreting QCA-analysis
Chaos in Time Dependent Variational Approximations to Quantum Dynamics
Dynamical chaos has recently been shown to exist in the Gaussian
approximation in quantum mechanics and in the self-consistent mean field
approach to studying the dynamics of quantum fields. In this study, we first
show that any variational approximation to the dynamics of a quantum system
based on the Dirac action principle leads to a classical Hamiltonian dynamics
for the variational parameters. Since this Hamiltonian is generically nonlinear
and nonintegrable, the dynamics thus generated can be chaotic, in distinction
to the exact quantum evolution. We then restrict attention to a system of two
biquadratically coupled quantum oscillators and study two variational schemes,
the leading order large N (four canonical variables) and Hartree (six canonical
variables) approximations. The chaos seen in the approximate dynamics is an
artifact of the approximations: this is demonstrated by the fact that its onset
occurs on the same characteristic time scale as the breakdown of the
approximations when compared to numerical solutions of the time-dependent
Schrodinger equation.Comment: 10 pages (12 figures), RevTeX (plus macro), uses epsf, minor typos
correcte
CP violation and the CKM angle from angular distributions of untagged decays governed by
We demonstrate that time-dependent studies of angular distributions for
decays caused by quark-level transitions extract
cleanly and model-independently the CKM angle . This CKM angle could be
cleanly determined from untagged decays alone, if the lifetime difference
between the mass eigenstates and is sizable. The
time-dependences for the relevant tagged and untagged observables are given
both in a general notation and in terms of linear polarization states and
should exhibit large CP-violating effects. These observables may furthermore
provide insights into the hadronization dynamics of the corresponding exclusive
decays thereby allowing tests of the factorization hypothesis.Comment: 14 pages, LaTeX, no figure
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