5,631 research outputs found
The Off-forward Quark-Quark Correlation Function
The properties of the non-forward quark-quark correlation function are
examined. We derive constraints on the correlation function from the
transformation properties of the fundamental fields of QCD occurring in its
definition. We further develop a method to construct an ansatz for this
correlator. We present the complete leading order set of generalized parton
distributions in terms of the amplitudes of the ansatz. Finally we conclude
that the number of independent generalized parton helicity changing
distributions is four.Comment: Accepted for publication in Physical Review
Algorithmic quantum simulation of memory effects
We propose a method for the algorithmic quantum simulation of memory effects
described by integrodifferential evolution equations. It consists in the
systematic use of perturbation theory techniques and a Markovian quantum
simulator. Our method aims to efficiently simulate both completely positive and
nonpositive dynamics without the requirement of engineering non-Markovian
environments. Finally, we find that small error bounds can be reached with
polynomially scaling resources, evaluated as the time required for the
simulation
The diffuse neutrino flux from the inner Galaxy: constraints from very high energy gamma-ray observations
Recently, the MILAGRO collaboration reported on the detection of a diffuse
multi-TeV emission from a region of the Galactic disk close to the inner
Galaxy. The emission is in excess of what is predicted by conventional models
for cosmic ray propagation, which are tuned to reproduce the spectrum of cosmic
rays observed locally. By assuming that the excess detected by MILAGRO is of
hadronic origin and that it is representative for the whole inner Galactic
region, we estimate the expected diffuse flux of neutrinos from a region of the
Galactic disk with coordinates . Our estimate has
to be considered as the maximal expected neutrino flux compatible with all the
available gamma ray data, since any leptonic contribution to the observed
gamma-ray emission would lower the neutrino flux. The diffuse flux of
neutrinos, if close to the maximum allowed level, may be detected by a
km--scale detector located in the northern hemisphere. A detection would
unambiguously reveal the hadronic origin of the diffuse gamma-ray emission.Comment: submitted to Astroparticle Physic
Pushing 1D CCSNe to explosions: model and SN 1987A
We report on a method, PUSH, for triggering core-collapse supernova
explosions of massive stars in spherical symmetry. We explore basic explosion
properties and calibrate PUSH such that the observables of SN1987A are
reproduced. Our simulations are based on the general relativistic hydrodynamics
code AGILE combined with the detailed neutrino transport scheme IDSA for
electron neutrinos and ALS for the muon and tau neutrinos. To trigger
explosions in the otherwise non-exploding simulations, we rely on the
neutrino-driven mechanism. The PUSH method locally increases the energy
deposition in the gain region through energy deposition by the heavy neutrino
flavors. Our setup allows us to model the explosion for several seconds after
core bounce. We explore the progenitor range 18-21M. Our studies
reveal a distinction between high compactness (HC) and low compactness (LC)
progenitor models, where LC models tend to explore earlier, with a lower
explosion energy, and with a lower remnant mass. HC models are needed to obtain
explosion energies around 1 Bethe, as observed for SN1987A. However, all the
models with sufficiently high explosion energy overproduce Ni. We
conclude that fallback is needed to reproduce the observed nucleosynthesis
yields. The nucleosynthesis yields of Ni depend sensitively on the
electron fraction and on the location of the mass cut with respect to the
initial shell structure of the progenitor star. We identify a progenitor and a
suitable set of PUSH parameters that fit the explosion properties of SN1987A
when assuming 0.1M of fallback. We predict a neutron star with a
gravitational mass of 1.50M. We find correlations between explosion
properties and the compactness of the progenitor model in the explored
progenitors. However, a more complete analysis will require the exploration of
a larger set of progenitors with PUSH.Comment: revised version as accepted by ApJ (results unchanged, text modified
for clarification, a few references added); 26 pages, 20 figure
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