1,819 research outputs found
On Nonlocality, Lattices and Internal Symmetries
We study functional analytic aspects of two types of correction terms to the
Heisenberg algebra. One type is known to induce a finite lower bound to the resolution of distances, a short distance cutoff which is motivated
from string theory and quantum gravity. It implies the existence of families of
self-adjoint extensions of the position operators with lattices of eigenvalues.
These lattices, which form representations of certain unitary groups cannot be
resolved on the given geometry. This leads us to conjecture that, within this
framework, degrees of freedom that correspond to structure smaller than the
resolvable (Planck) scale turn into internal degrees of freedom with these
unitary groups as symmetries. The second type of correction terms is related to
the previous essentially by "Wick rotation", and its basics are here considered
for the first time. In particular, we investigate unitarily inequivalent
representations.Comment: 6 pages, LaTe
Quantum gravity effects on statistics and compact star configurations
The thermodynamics of classical and quantum ideal gases based on the
Generalized uncertainty principle (GUP) are investigated. At low temperatures,
we calculate corrections to the energy and entropy. The equations of state
receive small modifications. We study a system comprised of a zero temperature
ultra-relativistic Fermi gas. It turns out that at low Fermi energy
, the degenerate pressure and energy are lifted. The
Chandrasekhar limit receives a small positive correction. We discuss the
applications on configurations of compact stars. As increases,
the radius, total number of fermions and mass first reach their nonvanishing
minima and then diverge. Beyond a critical Fermi energy, the radius of a
compact star becomes smaller than the Schwarzschild one. The stability of the
configurations is also addressed. We find that beyond another critical value of
the Fermi energy, the configurations are stable. At large radius, the increment
of the degenerate pressure is accelerated at a rate proportional to the radius.Comment: V2. discussions on the stability of star configurations added, 17
pages, 2 figures, typos corrected, version to appear in JHE
Harmonic oscillator with minimal length uncertainty relations and ladder operators
We construct creation and annihilation operators for harmonic oscillators
with minimal length uncertainty relations. We discuss a possible generalization
to a large class of deformations of cannonical commutation relations. We also
discuss dynamical symmetry of noncommutative harmonic oscillator.Comment: 8 pages, revtex4, final version, to appear in PR
Genetic comparison of Campylobacter coli resulting from pigs and poultry with isolates resulting from human campylobacteriosis
133 isolates of Campylobacter coli isolated from Brittany in France and collected in 2003 were analysed by RFLP/PFGE. They came from pig (65), poultry (56) and human campylobacteriosis (12). No pulsotype common to the 3 origins could be detected but the analysis of the genetic similarity at 80% of the isolates made it possible to build 19 groups of similarity in 3 cases. Poultry isolates were found in groups containing human isolates. Neverthless, the pig isolates were always in groups different from the poultry isolates and the human ones. These results tend to indicate that the two animal productions would have their own genotype and that the campylobacters from pigs are rarely responsible of human campylobacteriosis
On the geometry of quantum constrained systems
The use of geometric methods has proved useful in the hamiltonian description
of classical constrained systems. In this note we provide the first steps
toward the description of the geometry of quantum constrained systems. We make
use of the geometric formulation of quantum theory in which unitary
transformations (including time evolution) can be seen, just as in the
classical case, as finite canonical transformations on the quantum state space.
We compare from this perspective the classical and quantum formalisms and argue
that there is an important difference between them, that suggests that the
condition on observables to become physical is through the double commutator
with the square of the constraint operator. This provides a bridge between the
standard Dirac procedure --through its geometric implementation-- and the
Master Constraint program.Comment: 14 pages, no figures. Discussion expanded. Version published in CQ
Generalized Uncertainty Principle, Extra-dimensions and Holography
We consider Uncertainty Principles which take into account the role of
gravity and the possible existence of extra spatial dimensions. Explicit
expressions for such Generalized Uncertainty Principles in 4+n dimensions are
given and their holographic properties investigated. In particular, we show
that the predicted number of degrees of freedom enclosed in a given spatial
volume matches the holographic counting only for one of the available
generalizations and without extra dimensions.Comment: LaTeX, 13 pages, accepted for publication in Class. Quantum Gra
Motivic Serre invariants, ramification, and the analytic Milnor fiber
We show how formal and rigid geometry can be used in the theory of complex
singularities, and in particular in the study of the Milnor fibration and the
motivic zeta function. We introduce the so-called analytic Milnor fiber
associated to the germ of a morphism f from a smooth complex algebraic variety
X to the affine line. This analytic Milnor fiber is a smooth rigid variety over
the field of Laurent series C((t)). Its etale cohomology coincides with the
singular cohomology of the classical topological Milnor fiber of f; the
monodromy transformation is given by the Galois action. Moreover, the points on
the analytic Milnor fiber are closely related to the motivic zeta function of
f, and the arc space of X.
We show how the motivic zeta function can be recovered as some kind of Weil
zeta function of the formal completion of X along the special fiber of f, and
we establish a corresponding Grothendieck trace formula, which relates, in
particular, the rational points on the analytic Milnor fiber over finite
extensions of C((t)), to the Galois action on its etale cohomology.
The general observation is that the arithmetic properties of the analytic
Milnor fiber reflect the structure of the singularity of the germ f.Comment: Some minor errors corrected. The original publication is available at
http://www.springerlink.co
The Pivotal Role of Causality in Local Quantum Physics
In this article an attempt is made to present very recent conceptual and
computational developments in QFT as new manifestations of old and well
establihed physical principles. The vehicle for converting the
quantum-algebraic aspects of local quantum physics into more classical
geometric structures is the modular theory of Tomita. As the above named
laureate to whom I have dedicated has shown together with his collaborator for
the first time in sufficient generality, its use in physics goes through
Einstein causality. This line of research recently gained momentum when it was
realized that it is not only of structural and conceptual innovative power (see
section 4), but also promises to be a new computational road into
nonperturbative QFT (section 5) which, picturesquely speaking, enters the
subject on the extreme opposite (noncommutative) side.Comment: This is a updated version which has been submitted to Journal of
Physics A, tcilatex 62 pages. Adress: Institut fuer Theoretische Physik
FU-Berlin, Arnimallee 14, 14195 Berlin presently CBPF, Rua Dr. Xavier Sigaud
150, 22290-180 Rio de Janeiro, Brazi
Squeezed States in the de Sitter Vacuum
We discuss the treatment of squeezed states as excitations in the Euclidean
vacuum of de Sitter space. A comparison with the treatment of these states as
candidate no-particle states, or alpha-vacua, shows important differences
already in the free theory. At the interacting level alpha-vacua are
inconsistent, but squeezed state excitations seem perfectly acceptable. Indeed,
matrix elements can be renormalized in the excited states using precisely the
standard local counterterms of the Euclidean vacuum. Implications for
inflationary scenarios in cosmology are discussed.Comment: 15 pages, no figures. One new citation in version 3; no other change
Horizon Problem Remediation via Deformed Phase Space
We investigate the effects of a special kind of dynamical deformation between
the momenta of the scalar field of the Brans-Dicke theory and the scale factor
of the FRW metric. This special choice of deformation includes linearly a
deformation parameter. We trace the deformation footprints in the cosmological
equations of motion when the BD coupling parameter goes to infinity. One class
of the solutions gives a constant scale factor in the late time that confirms
the previous result obtained via another approach in the literature. This
effect can be interpreted as a quantum gravity footprint in the coarse grained
explanation. The another class of the solutions removes the big bang
singularity, and the accelerating expansion region has an infinite temporal
range which overcomes the horizon problem. After this epoch, there is a
graceful exiting by which the universe enters in the radiation dominated era.Comment: 13 pages, 2 figures, to appear in GER
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