4,635 research outputs found
Localizing the Latent Structure Canonical Uncertainty: Entropy Profiles for Hidden Markov Models
This report addresses state inference for hidden Markov models. These models
rely on unobserved states, which often have a meaningful interpretation. This
makes it necessary to develop diagnostic tools for quantification of state
uncertainty. The entropy of the state sequence that explains an observed
sequence for a given hidden Markov chain model can be considered as the
canonical measure of state sequence uncertainty. This canonical measure of
state sequence uncertainty is not reflected by the classic multivariate state
profiles computed by the smoothing algorithm, which summarizes the possible
state sequences. Here, we introduce a new type of profiles which have the
following properties: (i) these profiles of conditional entropies are a
decomposition of the canonical measure of state sequence uncertainty along the
sequence and makes it possible to localize this uncertainty, (ii) these
profiles are univariate and thus remain easily interpretable on tree
structures. We show how to extend the smoothing algorithms for hidden Markov
chain and tree models to compute these entropy profiles efficiently.Comment: Submitted to Journal of Machine Learning Research; No RR-7896 (2012
Sudden To Adiabatic Transition in Beta Decay
We discuss effects in beta decays at very low beta energies, of the order of
the kinetic energies of atomic electrons. As the beta energy is lowered the
atomic response changes from sudden to adiabatic. As a consequence, the beta
decay rate increases slightly and the ejection of atomic electrons (shake off)
and subsequent production of X rays is turned off. We estimate the transition
energy and the change in decay rate. The rate increase is largest in heavy
atoms, which have a small Q value in their decay. The X ray switch-off is
independent of Q value.Comment: 6 pages LaTe
Calculable Upper Limit on the Mass of the Lightest Higgs Boson in Any Perturbatively Valid Supersymmetric Theory
We show that there is a calculable upper limit on the mass of the lightest
Higgs boson in any supersymmetric theory that remains perturbative up to a high
scale . There are no restrictions on the Higgs sector, or the gauge group or
particle content. We estimate the value of the upper limit to be m_{\hcirc} <
146 GeV for 100 GeV < < 145 GeV, from all effects except possibly
additional heavy fermions beyond top (which could increase the limit by 0-20
GeV if any existed); for > 145 GeV the limit decreases monotonically. We
expect to be able to decrease the value of the upper limit by at least a few
percent by very careful analysis of the conditions. It is not normal in models
for the actual mass to saturate the upper limit.Comment: 8 pages, UM-TH-92-24, Plain TeX. (One table available by fax on
request to [email protected]
The Genetic Ancestry of African Americans, Latinos, and European Americans Across the United States
Over the past 500 years, North America has been the site of ongoing mixing of Native Americans, European settlers, and Africans (brought largely by the trans-Atlantic slave trade), shaping the early history of what became the United States. We studied the genetic ancestry of 5,269 self-described African Americans, 8,663 Latinos, and 148,789 European Americans who are 23andMe customers and show that the legacy of these historical interactions is visible in the genetic ancestry of present-day Americans. We document pervasive mixed ancestry and asymmetrical male and female ancestry contributions in all groups studied. We show that regional ancestry differences reflect historical events, such as early Spanish colonization, waves of immigration from many regions of Europe, and forced relocation of Native Americans within the US. This study sheds light on the fine-scale differences in ancestry within and across the United States and informs our understanding of the relationship between racial and ethnic identities and genetic ancestry
A CO Survey of Young Planetary Nebulae
We report the results of a sensitive survey of young planetary nebulae in the
CO J=2-1 line that significantly increases the available data on warm, dense,
molecular gas in the early phases of planetary nebula formation. The
observations were made using the IRAM 30 m telescope with the 3 by 3 pixel
Heterodyne Receiver Array (HERA). The array provides an effective means of
discriminating the CO emission of planetary nebulae in the galactic plane from
contaminating emission of interstellar clouds along the line of sight. 110
planetary nebulae were observed in the survey and 40 were detected. The results
increase the number of young planetary nebulae with known CO emission by
approximately a factor of two. The CO spectra yield radial velocities for the
detected nebulae, about half of which have uncertain or no velocity
measurements at optical wavelengths. The CO profiles range from parabolic to
double-peaked, tracing the evolution of structure in the molecular gas. The
line widths are significantly larger than on the Asymptotic Giant Branch, and
many of the lines show extended wings, which probably result from the effects
on the envelopes of high velocity jets.Comment: 29 pages, 2 figures (with multiple panels), to be published in
Astrophysical Journal Supplement Serie
On the equivalence of pairing correlations and intrinsic vortical currents in rotating nuclei
The present paper establishes a link between pairing correlations in rotating
nuclei and collective vortical modes in the intrinsic frame. We show that the
latter can be embodied by a simple S-type coupling a la Chandrasekhar between
rotational and intrinsic vortical collective modes. This results from a
comparison between the solutions of microscopic calculations within the HFB and
the HF Routhian formalisms. The HF Routhian solutions are constrained to have
the same Kelvin circulation expectation value as the HFB ones. It is shown in
several mass regions, pairing regimes, and for various spin values that this
procedure yields moments of inertia, angular velocities, and current
distributions which are very similar within both formalisms. We finally present
perspectives for further studies.Comment: 8 pages, 4 figures, submitted to Phys. Rev.
Heavy-Higgs Lifetime at Two Loops
The Standard-Model Higgs boson with mass decays almost
exclusively to pairs of and bosons. We calculate the dominant two-loop
corrections of to the partial widths of these decays. In
the on-mass-shell renormalization scheme, the correction factor is found to be
, where the second term is the
one-loop correction. We give full analytic results for all divergent two-loop
Feynman diagrams. A subset of finite two-loop vertex diagrams is computed to
high precision using numerical techniques. We find agreement with a previous
numerical analysis. The above correction factor is also in line with a recent
lattice calculation.Comment: 26 pages, 6 postscript figures. The complete paper including figures
is also available via WWW at
http://www.physik.tu-muenchen.de/tumphy/d/T30d/PAPERS/TUM-HEP-247-96.ps.g
The Higgs resonance in vector boson scattering
A heavy Higgs resonance is described in a representation-independent way
which is valid for the whole energy range of 2 -> 2 scattering processes,
including the asymptotic behavior at low and high energies. The low-energy
theorems which follow from to the custodial SU_2 symmetry of the Higgs sector
restrict the possible parameterizations of the lineshape that are consistent in
perturbation theory. Matching conditions are specified which are necessary and
sufficient to relate the parameters arising in different expansions. The
construction is performed explicitly up to next-to-leading order.Comment: 25 pages, revtex, uses epsf, amssym
Spallation Neutron Production by 0.8, 1.2 and 1.6 GeV Protons on various Targets
Spallation neutron production in proton induced reactions on Al, Fe, Zr, W,
Pb and Th targets at 1.2 GeV and on Fe and Pb at 0.8, and 1.6 GeV measured at
the SATURNE accelerator in Saclay is reported. The experimental
double-differential cross-sections are compared with calculations performed
with different intra-nuclear cascade models implemented in high energy
transport codes. The broad angular coverage also allowed the determination of
average neutron multiplicities above 2 MeV. Deficiencies in some of the models
commonly used for applications are pointed out.Comment: 20 pages, 32 figures, revised version, accepted fpr publication in
Phys. Rev.
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