33,926 research outputs found
Flat space modified particle dynamics induced by Loop Quantum Gravity
Starting from an heuristic approach to the semiclassical limit in loop
quantum gravity, the construction of effective Hamiltonians describing Planck
length corrections to the propagation of photons and spin 1/2 fermions, leading
to modified energy-momentum relations, is summarized. Assuming the existence of
a privileged reference frame, we also review the determination of stringent
bounds upon the parameters labelling such corrections, based upon already
existing experimental data, which are found to be from five to nine orders of
magnitude below the expected values.Comment: 10 pages, no figures, ws-procs 975x65.cls, extended version of the
talk given at the Tenth Marcel Grossmann Meeting, Rio de Janeiro, July 20-26,
200
Loop Quantum Gravity induced corrections to fermion dynamics in flat space
A summary of recent work related to the calculation of loop quantum gravity
induced corrections to standard particle (photons and spin 1/2 fermions)
dynamics in flat space is presented. Stringent bounds upon the parameters
characterizing the corrections in the fermionic sector, arising from already
known clock-comparison experiments, are reviewed.Comment: 6 pages, no figures, ws-procs9x6.tex, Talk presented at the Third
International Symposium on Quantum Theory and Symmetries, U. of Cincinnati,
September 10-14, 200
Solving CFTs with Weakly Broken Higher Spin Symmetry
The method of large spin perturbation theory allows to analyse conformal
field theories (CFT) by turning the crossing equations into an algebraic
problem. We apply this method to a generic CFT with weakly broken higher spin
(HS) symmetry, to the first non-trivial order in the breaking parameter. We
show that the spectrum of broken currents, for any value of the spin, follows
from crossing symmetry. After discussing a generic model of a single scalar
field, we focus on vector models with global symmetry. We rediscover the
spectrum of several models, including the Wilson-Fisher model around
four dimensions, the large model in and cubic models around six
dimensions, not necessarily unitary. We also discuss models where the
fundamental field is not part of the spectrum. Examples of this are weakly
coupled gauge theories and our method gives an on-shell gauge invariant way to
study them. At first order in the coupling constant we show that again the
spectrum follows from crossing symmetry, to all values of the spin. Our method
provides an alternative to usual perturbation theory without any reference to a
Lagrangian.Comment: 30 pages,v2:typos correcte
Loop quantum gravity induced modifications to particle dynamics
The construction of effective Hamiltonians arising from Loop Quantum Gravity
and incorporating Planck scale corrections to the dynamics of photons and spin
1/2 particles is summarized. The imposition of strict bounds upon some
parameters of the model using already existing experimental data is also
reviewed.Comment: 9 pages, 0 figures, talk presented at the X Mexican School of
Particles and Fields, latex, aipproc style 6x
Radio Continuum Sources Associated with AB Aur
We present high angular resolution, high-sensitivity Very Large Array
observations at 3.6 cm of the Herbig Ae star AB Aur. This star is of interest
since its circumstellar disk exhibits characteristics that have been attributed
to the presence of an undetected low mass companion or giant gas planet. Our
image confirms the continuum emission known to exist in association with the
star, and detects a faint protuberance that extends about to its
SE. Previous theoretical considerations and observational results are
consistent with the presence of a companion to AB Aur with the separation and
position angle derived from our radio data. We also determine the proper motion
of AB Aur by comparing our new observations with data taken about 17 years ago
and find values consistent with those found by Hipparcos.Comment: 6 pages, 1 figur
The superconformal bootstrap for structure constants
We report on non-perturbative bounds for structure constants on N=4 SYM. Such
bounds are obtained by applying the conformal bootstrap recently extended to
superconformal theories. We compare our results with interpolating functions
suitably restricted by the S-duality of the theory. Within numerical errors,
these interpolations support the conjecture that the bounds found in this paper
are saturated at duality invariant values of the coupling. This extends recent
conjectures for the anomalous dimension of leading twist operators.Comment: 14 pages, 4 figure
Conformal Bootstrap With Slightly Broken Higher Spin Symmetry
We consider conformal field theories with slightly broken higher spin
symmetry in arbitrary spacetime dimensions. We analyze the crossing equation in
the double light-cone limit and solve for the anomalous dimensions of higher
spin currents with large spin . The result depends on the
symmetries and the spectrum of the unperturbed conformal field theory. We
reproduce all known results and make further predictions. In particular we make
a prediction for the anomalous dimensions of higher spin currents in the 3d
Ising model.Comment: 41 pages, 2 figures, %\draftmod
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