98 research outputs found
Tensor Coordinates in Noncommutative Mechanics
A consistent classical mechanics formulation is presented in such a way that,
under quantization, it gives a noncommutative quantum theory with interesting
new features. The Dirac formalism for constrained Hamiltonian systems is
strongly used, and the object of noncommutativity plays
a fundamental rule as an independent quantity. The presented classical theory,
as its quantum counterpart, is naturally invariant under the rotation group
.Comment: 12 pages, Late
Kappa-deformed Snyder spacetime
We present Lie-algebraic deformations of Minkowski space with undeformed
Poincare algebra. These deformations interpolate between Snyder and
kappa-Minkowski space. We find realizations of noncommutative coordinates in
terms of commutative coordinates and derivatives. Deformed Leibniz rule, the
coproduct structure and star product are found. Special cases, particularly
Snyder and kappa-Minkowski in Maggiore-type realizations are discussed. Our
construction leads to a new class of deformed special relativity theories.Comment: 12 pages, no figures, LaTeX2e class file, accepted for publication in
Modern Physics Letters
KMS states on Quantum Grammars
We consider quantum (unitary) continuous time evolution of spins on a lattice
together with quantum evolution of the lattice itself. In physics such
evolution was discussed in connection with quantum gravity. It is also related
to what is called quantum circuits, one of the incarnations of a quantum
computer. We consider simpler models for which one can obtain exact
mathematical results. We prove existence of the dynamics in both Schroedinger
and Heisenberg pictures, construct KMS states on appropriate C*-algebras. We
show (for high temperatures) that for each system where the lattice undergoes
quantum evolution, there is a natural scaling leading to a quantum spin system
on a fixed lattice, defined by a renormalized Hamiltonian.Comment: 22 page
Enhanced thermal production of hard dileptons by processes
In the framework of the Hard Thermal Loop effective theory, we calculate the
two-loop contributions to hard lepton pair production in a quark-gluon plasma.
We show that the result is free of any infrared and collinear singularity. We
also recover the known fact that perturbation theory leads to integrable
singularities at the location of the threshold for . It
appears that the process calculated here significantly enhances the rate of low
mass hard dileptons.Comment: 32 latex pages, 14 postscript figure
Formulation, Interpretation and Application of non-Commutative Quantum Mechanics
In analogy with conventional quantum mechanics, non-commutative quantum
mechanics is formulated as a quantum system on the Hilbert space of
Hilbert-Schmidt operators acting on non-commutative configuration space. It is
argued that the standard quantum mechanical interpretation based on Positive
Operator Valued Measures, provides a sufficient framework for the consistent
interpretation of this quantum system. The implications of this formalism for
rotational and time reversal symmetry are discussed. The formalism is applied
to the free particle and harmonic oscillator in two dimensions and the physical
signatures of non commutativity are identified.Comment: 11 page
Signatures of Large Extra Dimensions
String theory suggests modifications of our spacetime such as extra
dimensions and the existence of a mininal length scale. In models with
addidional dimensions, the Planck scale can be lowered to values accessible by
future colliders. Effective theories which extend beyond the standart-model by
including extra dimensions and a minimal length allow computation of
observables and can be used to make testable predictions. Expected effects that
arise within these models are the production of gravitons and black holes.
Furthermore, the Planck-length is a lower bound to the possible resolution of
spacetime which might be reached soon.Comment: 8 pages, no figures, Talk presented at the NATO Advanced Study
Institute: Structure and Dynamics of Elementary Matter, Kemer, Turkey, 22 Sep
- 2 Oct 2003. Proceedings to be published by Kluwer Academic publisher
Numerical study of the coupled time-dependent Gross-Pitaevskii equation: Application to Bose-Einstein condensation
We present a numerical study of the coupled time-dependent Gross-Pitaevskii
equation, which describes the Bose-Einstein condensate of several types of
trapped bosons at ultralow temperature with both attractive and repulsive
interatomic interactions. The same approach is used to study both stationary
and time-evolution problems. We consider up to four types of atoms in the study
of stationary problems. We consider the time-evolution problems where the
frequencies of the traps or the atomic scattering lengths are suddenly changed
in a stable preformed condensate. We also study the effect of periodically
varying these frequencies or scattering lengths on a preformed condensate.
These changes introduce oscillations in the condensate which are studied in
detail. Good convergence is obtained in all cases studied.Comment: 9 pages, 10 figures, accepted in Physical Review
Southward migration of the zero-degree isotherm latitude over the Southern Ocean and the Antarctic Peninsula : cryospheric, biotic and societal implications
DATA AVAILABILITY : ERA5 temperature datasets can be downloaded from https://cds.climate.copernicus.eu/. CMIP6 climate projections can be downloaded from https://esgf-node.llnl.gov/search/cmip6/. The dataset generated in this research with the precipitation extremes for each model at every grid point and for different durations are available via González-Herrero, Sergi. (2023). Zero-degree isotherm latitude (ZIL) position over Antarctica: Historical and Projections [Data set]. Zenodo. doi:10.5281/zenodo.10046608. The codes used in this study are available via Sergi González Herrero. (2023). sergigonzalezh/ZIL-Antarctica: Zero-degree isotherm latitude (ZIL) position over Antarctica [Code] (1.0). Zenodo. doi:10.5281/zenodo.10063849.DATA AVAILABILITY : All data and codes are available in open access repositories.Please read abstract in the article.The research group ANTALP (Antarctic, Arctic, Alpine Environments; 2021 SGR 00269) funded by the Agència de Gestió d'Ajuts Universitaris i de Recerca of the Government of Catalonia; the project NEOGREEN (PID2020-113798GB-C31) funded by the Spanish Ministerio de Economía y Competitividad; Agencia Estatal de Investigación; the ASICS-South Africa Biodiversa project and institutional funds from UKRI-NERC.https://www.elsevier.com/locate/scitotenvhj2024Plant Production and Soil ScienceSDG-15:Life on lan
Photon Physics in Heavy Ion Collisions at the LHC
Various pion and photon production mechanisms in high-energy nuclear
collisions at RHIC and LHC are discussed. Comparison with RHIC data is done
whenever possible. The prospect of using electromagnetic probes to characterize
quark-gluon plasma formation is assessed.Comment: Writeup of the working group "Photon Physics" for the CERN Yellow
Report on "Hard Probes in Heavy Ion Collisions at the LHC", 134 pages. One
figure added in chapter 5 (comparison with PHENIX data). Some figures and
correponding text corrected in chapter 6 (off-chemical equilibrium thermal
photon rates). Some figures modified in chapter 7 (off-chemical equilibrium
photon rates) and comparison with PHENIX data adde
Magnetic fields in noncommutative quantum mechanics
We discuss various descriptions of a quantum particle on noncommutative space
in a (possibly non-constant) magnetic field. We have tried to present the basic
facts in a unified and synthetic manner, and to clarify the relationship
between various approaches and results that are scattered in the literature.Comment: Dedicated to the memory of Julius Wess. Work presented by F. Gieres
at the conference `Non-commutative Geometry and Physics' (Orsay, April 2007
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