5,080 research outputs found
Counting the number of correlated pairs in a nucleus
We suggest that the number of correlated nucleon pairs in an arbitrary
nucleus can be estimated by counting the number of proton-neutron,
proton-proton, and neutron-neutron pairs residing in a relative state. We
present numerical calculations of those amounts for the nuclei He,
Be, C, Al, Ca, Ca, Fe, Cu, Ag, and Au. The results are used to predict the
values of the ratios of the per-nucleon electron-nucleus inelastic scattering
cross section to the deuteron in the kinematic regime where correlations
dominate.Comment: 11 pages, 3 figure
Getting leverage on inflation with a large photometric redshift survey
We assess the potential of a future large-volume photometric redshift survey
to constrain observational inflationary parameters using three large-scale
structure observables: the angular shear and galaxy power spectra, and the
cluster mass function measured through weak lensing. When used in combination
with Planck-like CMB measurements, we find that the spectral index n_s can be
constrained to a 1 sigma precision of up to 0.0025. The sensitivity to the
running of the spectral index can potentially improve to 0.0017, roughly a
factor of five better than the present 1 sigma~constraint from Planck and
auxiliary CMB data, allowing us to test the assumptions of the slow-roll
scenario with unprecedented accuracy. Interestingly, neither CMB+shear nor
CMB+galaxy nor CMB+clusters alone can achieve this level of sensitivity; it is
the combined power of all three probes that conspires to break the different
parameter degeneracies inherent in each type of observations. We make our
forecast software publicly available via download or upon request from the
authors.Comment: 22 pages, 6 figures; the forecast software can be downloaded from
http://jhamann.web.cern.ch/jhamann/simdata/simdata.tar.g
Observing trans-Planckian ripples in the primordial power spectrum with future large scale structure probes
We revisit the issue of ripples in the primordial power spectra caused by
trans-Planckian physics, and the potential for their detection by future
cosmological probes. We find that for reasonably large values of the first
slow-roll parameter epsilon (> 0.001), a positive detection of trans-Planckian
ripples can be made even if the amplitude is as low as 10^-4. Data from the
Large Synoptic Survey Telescope (LSST) and the proposed future 21 cm survey
with the Fast Fourier Transform Telescope (FFTT) will be particularly useful in
this regard. If the scale of inflation is close to its present upper bound, a
scale of new physics as high as 0.2 M_Planck could lead to observable
signatures.Comment: 20 pages, 3 figures, uses iopart.cls; v2: 21 pages, added references,
to appear in JCA
Cosmological axion bounds
We discuss current cosmological constraints on axions, as well as future
sensitivities. Bounds on axion hot dark matter are discussed first, and
subsequently we discuss both current and future sensitivity to models in which
axions play the role as cold dark matter, but where the Peccei-Quinn symmetry
is not restored during reheating.Comment: 4 pages, 2 figures, To appear in the proceedings of 5th Patras
Workshop on Axions, WIMPs and WISPs, Durham 13-17 July 200
Cosmology seeking friendship with sterile neutrinos
Precision cosmology and big-bang nucleosynthesis mildly favor extra radiation
in the universe beyond photons and ordinary neutrinos, lending support to the
existence of low-mass sterile neutrinos. We use the WMAP 7-year data,
small-scale CMB observations from ACBAR, BICEP and QuAD, the SDSS 7th data
release, and measurement of the Hubble parameter from HST observations to
derive credible regions for the assumed common mass scale m_s and effective
number N_s of thermally excited sterile neutrino states. Our results are
compatible with the existence of one or perhaps two sterile neutrinos, as
suggested by LSND and MiniBooNE, if m_s is in the sub-eV range.Comment: 4 pages, 1 figure, matches version published in PR
Dark energy properties from large future galaxy surveys
We perform a detailed forecast on how well a {\sc Euclid}-like survey will be
able to constrain dark energy and neutrino parameters from a combination of its
cosmic shear power spectrum, galaxy power spectrum, and cluster mass function
measurements. We find that the combination of these three probes vastly
improves the survey's potential to measure the time evolution of dark energy.
In terms of a dark energy figure-of-merit defined as , we find a value of 690 for {\sc Euclid}-like data combined
with {\sc Planck}-like measurements of the cosmic microwave background (CMB)
anisotropies in a 10-dimensional cosmological parameter space, assuming a
CDM fiducial cosmology. For the more commonly used 7-parameter model,
we find a figure-of-merit of 1900 for the same data combination. We consider
also the survey's potential to measure dark energy perturbations in models
wherein the dark energy is parameterised as a fluid with a nonstandard
non-adiabatic sound speed, and find that in an \emph{optimistic} scenario in
which deviates by as much as is currently observationally allowed from
, models with and can be distinguished at more than significance. We emphasise that
constraints on the dark energy sound speed from cluster measurements are
strongly dependent on the modelling of the cluster mass function; significantly
weaker sensitivities ensue if we modify our model to include fewer features of
nonlinear dark energy clustering. Finally, we find that the sum of neutrino
masses can be measured with a precision of 0.015~eV, (abridged)Comment: 26 pages, 5 figures, matches JCAP versio
Radial Flow from Electromagnetic Probes and Signal of Quark Gluon Plasma
A first attempt has been made to extract the evolution of radial flow from
the analysis of the experimental data on electromagnetic probes experimentally
measured at SPS and RHIC energies. The spectra of photons and dileptons
measured by WA98 and NA60 collaborations respectively at CERN-SPS and the
photon spectra obtained by PHENIX collaboration at BNL-RHIC have been used to
constrain the theoretical models, rendering the outcome of the analysis largely
model independent. We argue that the variation of the radial velocity with
invariant mass is indicative of a phase transition from initially produced
partons to hadrons at SPS and RHIC energies.Comment: One LaTeX and 9 eps files, to appear in Phys. Rev.
Supervisory Control Synthesis of Discrete-Event Systems using Coordination Scheme
Supervisory control of discrete-event systems with a global safety
specification and with only local supervisors is a difficult problem. For
global specifications the equivalent conditions for local control synthesis to
equal global control synthesis may not be met. This paper formulates and solves
a control synthesis problem for a generator with a global specification and
with a combination of a coordinator and local controllers. Conditional
controllability is proven to be an equivalent condition for the existence of
such a coordinated controller. A procedure to compute the least restrictive
solution is also provided in this paper and conditions are stated under which
the result of our procedure coincides with the supremal controllable
sublanguage.Comment: 29 pages, 11 figure
Future cosmological sensitivity for hot dark matter axions
We study the potential of a future, large-volume photometric survey to
constrain the axion mass in the hot dark matter limit. Future surveys
such as Euclid will have significantly more constraining power than current
observations for hot dark matter. Nonetheless, the lowest accessible axion
masses are limited by the fact that axions lighter than eV decouple
before the QCD epoch, assumed here to occur at a temperature MeV; this leaves an axion population of such low density that its
late-time cosmological impact is negligible. For larger axion masses, eV, where axions remain in equilibrium until after the QCD phase
transition, we find that a Euclid-like survey combined with Planck CMB data can
detect at very high significance. Our conclusions are robust against
assumptions about prior knowledge of the neutrino mass. Given that the proposed
IAXO solar axion search is sensitive to eV, the axion mass
range probed by cosmology is nicely complementary.Comment: 17 pages, 5 figure
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