1,321 research outputs found
Quantum Field Theory with Nonzero Minimal Uncertainties in Positions and Momenta
A noncommutative geometric generalisation of the quantum field theoretical
framework is developed by generalising the Heisenberg commutation relations.
There appear nonzero minimal uncertainties in positions and in momenta. As the
main result it is shown with the example of a quadratically ultraviolet
divergent graph in theory that nonzero minimal uncertainties in
positions do have the power to regularise. These studies are motivated with the
ansatz that nonzero minimal uncertainties in positions and in momenta arise
from gravity. Algebraic techniques are used that have been developed in the
field of quantum groups.Comment: 52 pages LATEX, DAMTP/93-33. Revised version now includes a chapter
on the Poincare algebra and curvature as noncommutativity of momentum spac
Perturbation spectrum in inflation with cutoff
It has been pointed out that the perturbation spectrum predicted by inflation
may be sensitive to a natural ultraviolet cutoff, thus potentially providing an
experimentally accessible window to aspects of Planck scale physics. A priori,
a natural ultraviolet cutoff could take any form, but a fairly general
classification of possible Planck scale cutoffs has been given. One of those
categorized cutoffs, also appearing in various studies of quantum gravity and
string theory, has recently been implemented into the standard inflationary
scenario. Here, we continue this approach by investigating its effects on the
predicted perturbation spectrum. We find that the size of the effect depends
sensitively on the scale separation between cutoff and horizon during
inflation.Comment: 6 pages; matches version accepted by PR
Mode Generating Mechanism in Inflation with Cutoff
In most inflationary models, space-time inflated to the extent that modes of
cosmological size originated as modes of wavelengths at least several orders of
magnitude smaller than the Planck length. Recent studies confirmed that,
therefore, inflationary predictions for the cosmic microwave background
perturbations are generally sensitive to what is assumed about the Planck
scale. Here, we propose a framework for field theories on curved backgrounds
with a plausible type of ultraviolet cutoff. We find an explicit mechanism by
which during cosmic expansion new (comoving) modes are generated continuously.
Our results allow the numerical calculation of a prediction for the CMB
perturbation spectrum.Comment: 9 pages, LaTe
The Minimal Length and Large Extra Dimensions
Planck scale physics represents a future challenge, located between particle
physics and general relativity. The Planck scale marks a threshold beyond which
the old description of spacetime breaks down and conceptually new phenomena
must appear. Little is known about the fundamental theory valid at Planckian
energies, except that it necessarily seems to imply the occurrence of a minimal
length scale, providing a natural ultraviolet cutoff and a limit to the
possible resolution of spacetime.
Motivated by String Theory, the models of large extra dimensions lower the
Planck scale to values soon accessible. These models predict a vast number of
quantum gravity effects at the lowered Planck scale, among them the production
of TeV-mass black holes and gravitons. Within the extra dimensional scenario,
also the minimal length comes into the reach of experiment and sets a
fundamental limit to short distance physics.
We review the status of Planck scale physics in these effective models.Comment: 18 pages, 5 figures, brief review to appear in Mod. Phys. Let.
Modelling a scale-based strontium isotope baseline for Hungary
Strontium isotope analysis has recently proven to be a useful tool to elucidate population movements and subsistence strategies in ecological and archaeological sciences. The interpretation depends on the size, type, availability, and preservation of the sample and the reliability of the produced strontium isotope baseline. However, collecting quantitatively and qualitatively suitable baseline samples is considered a challenging task in archaeological research. To meet these challenges, we introduce an innovative analytical technique, which enables the analysis of small sample sizes from heterogeneous site distribution and environmental settings. This article integrates multivariate environmental modelling and bioarchaeological data of 49 sites to establish the first scale-based differentiation between site-specific and micro-regional strontium isotope baselines with various sample sizes in Hungary. In future mobility studies, this approach will allow distinguishing human and faunal movement ranges on different geographical scales.Strontium isotope analysis has recently proven to be a useful tool to elucidate population movements and subsistence strategies in ecological and archaeological sciences. The interpretation depends on the size, type, availability, and preservation of the sample and the reliability of the produced strontium isotope baseline. However, collecting quantitatively and qualitatively suitable baseline samples is considered a challenging task in archaeological research. To meet these challenges, we introduce an innovative analytical technique, which enables the analysis of small sample sizes from heterogeneous site distribution and environmental settings. This article integrates multivariate environmental modelling and bioarchaeological data of 49 sites to establish the first scale-based differentiation between site-specific and micro-regional strontium isotope baselines with various sample sizes in Hungary. In future mobility studies, this approach will allow distinguishing human and faunal movement ranges on different geographical scales
Field theory on evolving fuzzy two-sphere
I construct field theory on an evolving fuzzy two-sphere, which is based on
the idea of evolving non-commutative worlds of the previous paper. The
equations of motion are similar to the one that can be obtained by dropping the
time-derivative term of the equation derived some time ago by Banks, Peskin and
Susskind for pure-into-mixed-state evolutions. The equations do not contain an
explicit time, and therefore follow the spirit of the Wheeler-de Witt equation.
The basic properties of field theory such as action, gauge invariance and
charge and momentum conservation are studied. The continuum limit of the scalar
field theory shows that the background geometry of the corresponding continuum
theory is given by ds^2 = -dt^2+ t d Omega^2, which saturates locally the
cosmic holographic principle.Comment: Typos corrected, minor changes, 23 pages, no figures, LaTe
On Signatures of Short Distance Physics in the Cosmic Microwave Background
Following a self-contained review of the basics of the theory of cosmological
perturbations, we discuss why the conclusions reached in the recent paper by
Kaloper et al are too pessimistic estimates of the amplitude of possible
imprints of trans-Planckian (string) physics on the spectrum of cosmic
microwave anisotropies in an inflationary Universe. It is shown that the likely
origin of large trans-Planckian effects on late time cosmological fluctuations
comes from nonadiabatic evolution of the state of fluctuations while the
wavelength is smaller than the Planck (string) scale, resulting in an excited
state at the time that the wavelength crosses the Hubble radius during
inflation.Comment: 11 pages, 4 figure
The Corley-Jacobson dispersion relation and trans-Planckian inflation
In this Letter we study the dependence of the spectrum of fluctuations in
inflationary cosmology on possible effects of trans-Planckian physics, using
the Corley/Jacobson dispersion relations as an example. We compare the methods
used in previous work [1] with the WKB approximation, give a new exact
analytical result, and study the dependence of the spectrum obtained using the
approximate method of Ref. [1] on the choice of the matching time between
different time intervals. We also comment on recent work subsequent to Ref. [1]
on the trans-Planckian problem for inflationary cosmology.Comment: 6 pages, Revtex
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