28 research outputs found
Causality and statistics on the Groenewold-Moyal plane
Quantum theories constructed on the noncommutative spacetime called the
Groenewold-Moyal plane exhibit many interesting properties such as Lorentz and
CPT noninvariance, causality violation and twisted statistics. We show that
such violations lead to many striking features that may be tested
experimentally. These theories predict Pauli forbidden transitions due to
twisted statistics, anisotropies in the cosmic microwave background radiation
due to correlations of observables in spacelike regions and Lorentz and CPT
violations in scattering amplitudes.Comment: 12 pages, 1 figure. Based on the talk given by APB at the Workshop
"Theoretical and Experimental Aspects of the Spin Statisics Connection and
Related Symmetries", Stazione Marittima Conference Center, Trieste, Italy
from the 21st to the 25th of October 200
Quantum Fields on the Groenewold-Moyal Plane
We give an introductory review of quantum physics on the noncommutative
spacetime called the Groenewold-Moyal plane. Basic ideas like star products,
twisted statistics, second quantized fields and discrete symmetries are
discussed. We also outline some of the recent developments in these fields and
mention where one can search for experimental signals.Comment: 50 pages, 3 figures. v2: published versio
Thermofield Dynamics for Twisted Poincare-Invariant Field Theories: Wick Theorem and S-matrix
Poincare invariant quantum field theories can be formulated on
non-commutative planes if the statistics of fields is twisted. This is
equivalent to state that the coproduct on the Poincare group is suitably
twisted. In the present work we present a twisted Poincare invariant quantum
field theory at finite temperature. For that we use the formalism of
Thermofield Dynamics (TFD). This TFD formalism is extend to incorporate
interacting fields. This is a non trivial step, since the separation in
positive and negative frequency terms is no longer valid in TFD. In particular,
we prove the validity of Wick's theorem for twisted scalar quantum field at
finite temperature.Comment: v1: 25 pages, no figure v2: references added; typos corrected; typo
in title correcte
CMB constraints on noncommutative geometry during inflation
We investigate the primordial power spectrum of the density perturbations
based on the assumption that spacetime is noncommutative in the early stage of
inflation. Due to the spacetime noncommutativity, the primordial power spectrum
can lose rotational invariance. Using the k-inflation model and slow-roll
approximation, we show that the deviation from rotational invariance of the
primordial power spectrum depends on the size of noncommutative length scale
L_s but not on sound speed. We constrain the contributions from the spacetime
noncommutativity to the covariance matrix for the harmonic coefficients of the
CMB anisotropies using five-year WMAP CMB maps. We find that the upper bound
for L_s depends on the product of sound speed and slow-roll parameter.
Estimating this product using cosmological parameters from the five-year WMAP
results, the upper bound for L_s is estimated to be less than 10^{-27} cm at
99.7% confidence level.Comment: 8 pages, 1 figure, References added, Accepted for publication in EPJC
(submitted version
Wedge-Local Quantum Fields and Noncommutative Minkowski Space
Within the setting of a recently proposed model of quantum fields on
noncommutative Minkowski spacetime, the consequences of the consistent
application of the proper, untwisted Poincare group as the symmetry group are
investigated. The emergent model contains an infinite family of fields which
are labelled by different noncommutativity parameters, and related to each
other by Lorentz transformations. The relative localization properties of these
fields are investigated, and it is shown that to each field one can assign a
wedge-shaped localization region of Minkowski space. This assignment is
consistent with the principles of covariance and locality, i.e. fields
localized in spacelike separated wedges commute.
Regarding the model as a non-local, but wedge-local, quantum field theory on
ordinary (commutative) Minkowski spacetime, it is possible to determine
two-particle S-matrix elements, which turn out to be non-trivial. Some partial
negative results concerning the existence of observables with sharper
localization properties are also obtained.Comment: Version to appear in JHEP, 27 page
Cosmological and Black Hole Spacetimes in Twisted Noncommutative Gravity
We derive noncommutative Einstein equations for abelian twists and their
solutions in consistently symmetry reduced sectors, corresponding to twisted
FRW cosmology and Schwarzschild black holes. While some of these solutions must
be rejected as models for physical spacetimes because they contradict
observations, we find also solutions that can be made compatible with low
energy phenomenology, while exhibiting strong noncommutativity at very short
distances and early times.Comment: LaTeX 12 pages, JHEP.st
Constraints from CMB on Spacetime Noncommutativity and Causality Violation
We try to constrain the noncommutativity length scale of the theoretical
model given in Ref. [1] using the observational data from ACBAR, CBI and five
year WMAP. The noncommutativity parameter is not constrained by WMAP data,
however ACBAR and CBI data restrict the lower bound of its energy scale to be
around 10 TeV. We also derive an expression for the amount of non-causality
coming from spacetime noncommutativity for the fields of primordial scalar
perturbations that are space-like separated. The amount of causality violation
for these field fluctuations are direction dependent.Comment: 15 pages, 6 figure
Noncommutative field gas driven inflation
We investigate early time inflationary scenarios in an Universe filled with a
dilute noncommutative bosonic gas at high temperature. A noncommutative bosonic
gas is a gas composed of bosonic scalar field with noncommutative field space
on a commutative spacetime. Such noncommutative field theories was recently
introduced as a generalization of quantum mechanics on a noncommutative
spacetime. As key features of these theories are Lorentz invariance violation
and CPT violation. In the present study we use a noncommutative bosonic field
theory that besides the noncommutative parameter shows up a further
parameter . This parameter controls the range of the
noncommutativity and acts as a regulator for the theory. Both parameters play a
key role in the modified dispersion relations of the noncommutative bosonic
field, leading to possible striking consequences for phenomenology. In this
work we obtain an equation of state for the
noncommutative bosonic gas relating pressure and energy density , in
the limit of high temperature. We analyse possible behaviours for this gas
parameters , and , so that , which
is the region where the Universe enters an accelerated phase.Comment: Reference added. Version to appear in Journal of Cosmology and
Astroparticle Physics - JCA