933 research outputs found
Microwave ISM Emission Observed by WMAP
We investigate the nature of the diffuse Galactic emission in the Wilkinson
Microwave Anisotropy Probe (WMAP) temperature anisotropy data. Substantial
dust-correlated emission is observed at all WMAP frequencies, far exceeding the
expected thermal dust emission in the lowest frequency channels (23, 33, 41
GHz). The WMAP team (Bennett et al.) interpret this emission as dust-correlated
synchrotron radiation, attributing the correlation to the natural association
of relativistic electrons produced by SNae with massive star formation in dusty
clouds, and deriving an upper limit of 5% on the contribution of Draine &
Lazarian spinning dust at K-band (23 GHz). We pursue an alternative
interpretation that much, perhaps most, of the dust-correlated emission at
these frequencies is indeed spinning dust, and explore the spectral dependence
on environment by considering a few specific objects as well as the full sky
average. Models similar to Draine & Lazarian spinning dust provide a good fit
to the full-sky data. The full-sky fit also requires a significant component
with free-free spectrum uncorrelated with \Halpha, possibly hot (~million K)
gas within 30 degrees of the Galactic center.Comment: ApJ in press (accepted 5 Dec 2003), version 2: corrected typos and
added references. 23 pages, 5 figures, 2 tables. Free-free haze map is
available at http://skymaps.inf
Detecting Dark Matter Annihilation with CMB Polarization : Signatures and Experimental Prospects
Dark matter (DM) annihilation during hydrogen recombination (z ~ 1000) will
alter the recombination history of the Universe, and affect the observed CMB
temperature and polarization fluctuations. Unlike other astrophysical probes of
DM, this is free of the significant uncertainties in modelling galactic
physics, and provides a method to detect and constrain the cosmological
abundances of these particles. We parametrize the effect of DM annihilation as
an injection of ionizing energy at a rate e_{dm}, and argue that this simple
"on the spot'' modification is a good approximation to the complicated
interaction of the annihilation products with the photon-electron plasma.
Generic models of DM do not change the redshift of recombination, but change
the residual ionization after recombination. This broadens the surface of last
scattering, suppressing the temperature fluctuations and enhancing the
polarization fluctuations. We use the temperature and polarization angular
power spectra to measure these deviations from the standard recombination
history, and therefore, indirectly probe DM annihilation. (abridged)Comment: 13 pages, 8 figures, submitted to PR
Pseudo-Dipole Signal Removal from WMAP Data
It is discovered in our previous work that different observational
systematics, e.g., errors of antenna pointing directions, asynchronous between
the attitude and science data, can generate pseudo-dipole signal in full-sky
maps of the cosmic microwave background (CMB) anisotropy published by The
Wilkinson Microwave Anisotropy Probe (WMAP) team. Now the antenna sidelobe
response to the Doppler signal is found to be able to produce similar effect as
well. In this work, independent to the sources, we uniformly model the
pseudo-dipole signal and remove it from published WMAP7 CMB maps by model
fitting. The result demonstrates that most of the released WMAP CMB quadrupole
is artificial.Comment: V3: using WMAP7 dat
Cosmic Neutrino Bound on the Dark Matter Annihilation Rate in the Late Universe
How large can the dark matter self-annihilation rate in the late universe be?
This rate depends on (rho_DM/m_chi)^2 , where rho_DM/m_chi is the
number density of dark matter, and the annihilation cross section is averaged
over the velocity distribution. Since the clustering of dark matter is known,
this amounts to asking how large the annihilation cross section can be.
Kaplinghat, Knox, and Turner proposed that a very large annihilation cross
section could turn a halo cusp into a core, improving agreement between
simulations and observations; Hui showed that unitarity prohibits this for
large dark matter masses. We show that if the annihilation products are
Standard Model particles, even just neutrinos, the consequent fluxes are ruled
out by orders of magnitude, even at small masses. Equivalently, to invoke such
large annihilation cross sections, one must now require that essentially no
Standard Model particles are produced.Comment: 4 pages, 2 figures; to appear in the proceedings of the TeV Particle
Astrophysics II Workshop, Madison, Wisconsin, 28-31 Aug 200
Realizing Omega-regular Hyperproperties
We studied the hyperlogic HyperQPTL, which combines the concepts of trace
relations and -regularity. We showed that HyperQPTL is very expressive,
it can express properties like promptness, bounded waiting for a grant,
epistemic properties, and, in particular, any -regular property. Those
properties are not expressible in previously studied hyperlogics like HyperLTL.
At the same time, we argued that the expressiveness of HyperQPTL is optimal in
a sense that a more expressive logic for -regular hyperproperties would
have an undecidable model checking problem. We furthermore studied the
realizability problem of HyperQPTL. We showed that realizability is decidable
for HyperQPTL fragments that contain properties like promptness. But still, in
contrast to the satisfiability problem, propositional quantification does make
the realizability problem of hyperlogics harder. More specifically, the
HyperQPTL fragment of formulas with a universal-existential propositional
quantifier alternation followed by a single trace quantifier is undecidable in
general, even though the projection of the fragment to HyperLTL has a decidable
realizability problem. Lastly, we implemented the bounded synthesis problem for
HyperQPTL in the prototype tool BoSy. Using BoSy with HyperQPTL specifications,
we have been able to synthesize several resource arbiters. The synthesis
problem of non-linear-time hyperlogics is still open. For example, it is not
yet known how to synthesize systems from specifications given in branching-time
hyperlogics like HyperCTL.Comment: International Conference on Computer Aided Verification (CAV 2020
The white dwarf in dwarf nova SDSS J080434.20+510349.2: Entering the instability strip?
SDSS J080434.20+510349.2 is the WZ type binary that displayed rare outburst
in 2006 (Pavlenko et al., 2007). During the long-lasting tail of the late stage
of the outburst binary shown the two-humped or four-humped profile of the
orbital light modulation. The amplitude of orbital light curve decreased while
the mean brightness decreased, more over that occurred 10 times faster
during the fast outburst decline in respect to the late quiet state of slow
outburst fading. There were no white dwarf pulsations detected neither 1 - 1.5
months prior to the outburst nor in 1.5 - 2 months after the 2006 outburst in
this system. However the strong non-radial pulsations with period 12.6 minutes
and mean amplitude of 0.05^m were first detected in V band with 2.6-m Shajn
mirror telescope of the Crimean astrophysical observatory in ~ 8 months after
the outburst. The evolution of pulsations over two years in 2006 - 2008 is
considered. It is supposed that pulsations first appeared when the cooling
white dwarf (after the outburst) entered the instability strip although the
possibility of temporary lack of pulsations at some occasions also could not be
excluded.Comment: Submitted to Proceedings of 16th European White Dwarf Workshop
(EUROWD08
Synthesizing Finite-state Protocols from Scenarios and Requirements
Scenarios, or Message Sequence Charts, offer an intuitive way of describing
the desired behaviors of a distributed protocol. In this paper we propose a new
way of specifying finite-state protocols using scenarios: we show that it is
possible to automatically derive a distributed implementation from a set of
scenarios augmented with a set of safety and liveness requirements, provided
the given scenarios adequately \emph{cover} all the states of the desired
implementation. We first derive incomplete state machines from the given
scenarios, and then synthesis corresponds to completing the transition relation
of individual processes so that the global product meets the specified
requirements. This completion problem, in general, has the same complexity,
PSPACE, as the verification problem, but unlike the verification problem, is
NP-complete for a constant number of processes. We present two algorithms for
solving the completion problem, one based on a heuristic search in the space of
possible completions and one based on OBDD-based symbolic fixpoint computation.
We evaluate the proposed methodology for protocol specification and the
effectiveness of the synthesis algorithms using the classical alternating-bit
protocol.Comment: This is the working draft of a paper currently in submission.
(February 10, 2014
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