347 research outputs found
Statistical mechanical aspects of joint source-channel coding
An MN-Gallager Code over Galois fields, , based on the Dynamical Block
Posterior probabilities (DBP) for messages with a given set of autocorrelations
is presented with the following main results: (a) for a binary symmetric
channel the threshold, , is extrapolated for infinite messages using the
scaling relation for the median convergence time, ;
(b) a degradation in the threshold is observed as the correlations are
enhanced; (c) for a given set of autocorrelations the performance is enhanced
as is increased; (d) the efficiency of the DBP joint source-channel coding
is slightly better than the standard gzip compression method; (e) for a given
entropy, the performance of the DBP algorithm is a function of the decay of the
correlation function over large distances.Comment: 6 page
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Helicity-selective phase-matching and quasi-phase matching of circularly polarized high-order harmonics: Towards chiral attosecond pulses
Phase matching of circularly polarized high-order harmonics driven by counter-rotating bi-chromatic lasers was recently predicted theoretically and demonstrated experimentally. In that work, phase matching was analyzed by assuming that the total energy, spin angular momentum and linear momentum of the photons participating in the process are conserved. Here we propose a new perspective on phase matching of circularly polarized high harmonics. We derive an extended phase matching condition by requiring a new propagation matching condition between the classical vectorial bi-chromatic laser pump and harmonics fields. This allows us to include the influence of the laser pulse envelopes on phase matching. We find that the helicity dependent phase matching facilitates generation of high harmonics beams with a high degree of chirality. Indeed, we present an experimentally measured chiral spectrum that can support a train of attosecond pulses with a high degree of circular polarization. Moreover, while the degree of circularity of the most intense pulse approaches unity, all other pulses exhibit reduced circularity. This feature suggests the possibility of using a train of attosecond pulses as an isolated attosecond probe for chiral-sensitive experiments
Violence in Hasmonean Judea : Skeletal evidence of a massacre from 2ndâst century BCE Jerusalem
Partial funding for JD to complete this research was provided by Darwin College, University of Cambridge. The authors would like to thank Craig Cessford of the Cambridge Archaeological Unit for his assistance with the radiocarbon dates, David Errickson of Cranfield University for aiding in the analysis of the tool marks, and the reviewers for their comments on this manuscript. The excavation was carried out by the Israel Antiquities Authority (Permit number A7929) and supported by the Bezalel Academy of Art and Design.Peer reviewedPublisher PD
A fixed-point property of logic-based bargaining solution
Abstract. This paper presents a logic-based bargaining solution based on Zhang and Zhangâs framework. It is shown that if the demand sets of players are logically closed, the solution satisfies a fixed-point property, which says that the outcome of bargaining is the result of mutual belief revision. The result is interesting not only because it presents a desirable logical property of bargaining solution but also establishes a link between bargaining theory and multi-agent belief revision.
Nanoscale magnetic imaging using circularly polarized high-harmonic radiation
This work demonstrates nanoscale magnetic imaging using bright circularly polarized high-harmonic radiation. We utilize the magneto-optical contrast of worm-like magnetic domains in a Co/Pd multilayer structure, obtaining quantitative amplitude and phase maps by lensless imaging. A diffraction-limited spatial resolution of 49 nm is achieved with iterative phase reconstruction enhanced by a holographic mask. Harnessing the exceptional coherence of high harmonics, this approach will facilitate quantitative, element-specific, and spatially resolved studies of ultrafast magnetization dynamics, advancing both fundamental and applied aspects of nanoscale magnetism
CP violation Beyond the MSSM: Baryogenesis and Electric Dipole Moments
We study electroweak baryogenesis and electric dipole moments in the presence
of the two leading-order, non-renormalizable operators in the Higgs sector of
the MSSM. Significant qualitative and quantitative differences from MSSM
baryogenesis arise due to the presence of new CP-violating phases and to the
relaxation of constraints on the supersymmetric spectrum (in particular, both
stops can be light). We find: (1) spontaneous baryogenesis, driven by a change
in the phase of the Higgs vevs across the bubble wall, becomes possible; (2)
the top and stop CP-violating sources can become effective; (3) baryogenesis is
viable in larger parts of parameter space, alleviating the well-known
fine-tuning associated with MSSM baryogenesis. Nevertheless, electric dipole
moments should be measured if experimental sensitivities are improved by about
one order of magnitude.Comment: 33 pages, 6 figure
Scalar-mediated forward-backward asymmetry
A large forward-backward asymmetry in production, for large
invariant mass of the system, has been recently observed by the CDF
collaboration. Among the scalar mediated mechanisms that can explain such a
large asymmetry, only the t-channel exchange of a color-singlet weak-doublet
scalar is consistent with both differential and integrated cross
section measurements. Constraints from flavor changing processes dictate a very
specific structure for the Yukawa couplings of such a new scalar. No sizable
deviation in the differential or integrated production cross section
is expected at the LHC.Comment: 22 pages, 1 figure and 2 tables. v2: Corrected Eqs.(50,51,74),
adapted Fig.1, Tab.1 and relevant discussions. Extended discussion of top
decay and single to
2:1 for Naturalness at the LHC?
A large enhancement of a factor of 1.5 - 2 in Higgs production and decay in
the diphoton channel, with little deviation in the ZZ channel, can only
plausibly arise from a loop of new charged particles with large couplings to
the Higgs. We show that, allowing only new fermions with marginal interactions
at the weak scale, the required Yukawa couplings for a factor of 2 enhancement
are so large that the Higgs quartic coupling is pushed to large negative values
in the UV, triggering an unacceptable vacuum instability far beneath the 10 TeV
scale. An enhancement by a factor of 1.5 can be accommodated if the charged
fermions are lighter than 150 GeV, within reach of discovery in almost all
cases in the 8 TeV run at the LHC, and in even the most difficult cases at 14
TeV. Thus if the diphoton enhancement survives further scrutiny, and no charged
fermions beneath 150 GeV are found, there must be new bosons far beneath the 10
TeV scale. This would unambiguously rule out a large class of fine-tuned
theories for physics beyond the Standard Model, including split SUSY and many
of its variants, and provide strong circumstantial evidence for a natural
theory of electroweak symmetry breaking at the TeV scale. Alternately, theories
with only a single fine-tuned Higgs and new fermions at the weak scale, with no
additional scalars or gauge bosons up to a cutoff much larger than the 10 TeV
scale, unambiguously predict that the hints for a large diphoton enhancement in
the current data will disappear.Comment: 18 pages, 6 figures; typos corrected and references adde
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