5,747 research outputs found
Bounds on Long-Lived Relics from Diffuse Gamma Ray Observations
We place bounds on long-lived primordial relics using measurements of the
diffuse gamma ray spectrum from EGRET and COMPTEL. Bounds are derived for both
radiative and hadronic decays with stronger bounds applying for the latter
decay mode. We present an exclusion plot in the relic density-lifetime plane
that shows nontrivial dependence on the mass of the relic. The violations of
scaling with mass are a consequence of the different possible scattering
processes which lead to differing electromagnetic showering profiles. The
tightest bounds for shorter lifetimes come from COMPTEL observations of the low
energy part of the spectrum, while for longer lifetimes the highest observable
energy at EGRET gives the tightest bounds. We discuss the implications of the
bounds for dark matter candidates as well as relics that have a mass density
substantially below the critical density. These bounds can be utilized to
eliminate models that contain relics with lifetimes longer than times
the age of the universe.Comment: 31 pages, LaTeX, uses epsf.sty, 12 figures. Figs. 8-12 replaced to
correct a normalization problem; bounds slightly modified, conclusions
unchanged; minor typos correcte
Finite mixtures of matrix-variate Poisson-log normal distributions for three-way count data
Three-way data structures, characterized by three entities, the units, the
variables and the occasions, are frequent in biological studies. In RNA
sequencing, three-way data structures are obtained when high-throughput
transcriptome sequencing data are collected for n genes across p conditions at
r occasions. Matrix-variate distributions offer a natural way to model
three-way data and mixtures of matrix-variate distributions can be used to
cluster three-way data. Clustering of gene expression data is carried out as
means to discovering gene co-expression networks. In this work, a mixture of
matrix-variate Poisson-log normal distributions is proposed for clustering read
counts from RNA sequencing. By considering the matrix-variate structure, full
information on the conditions and occasions of the RNA sequencing dataset is
simultaneously considered, and the number of covariance parameters to be
estimated is reduced. A Markov chain Monte Carlo expectation-maximization
algorithm is used for parameter estimation and information criteria are used
for model selection. The models are applied to both real and simulated data,
giving favourable clustering results
Investigation of the feasibility of sterile assembly of silver-zinc batteries
Electrical performance, bioassays, and packaging concepts evaluated in sterile assembly of silver zinc batterie
Renormalization Group Treatment of Nonrenormalizable Interactions
The structure of the UV divergencies in higher dimensional nonrenormalizable
theories is analysed. Based on renormalization operation and renormalization
group theory it is shown that even in this case the leading divergencies
(asymptotics) are governed by the one-loop diagrams the number of which,
however, is infinite. Explicit expression for the one-loop counter term in an
arbitrary D-dimensional quantum field theory without derivatives is suggested.
This allows one to sum up the leading asymptotics which are independent of the
arbitrariness in subtraction of higher order operators. Diagrammatic
calculations in a number of scalar models in higher loops are performed to be
in agreement with the above statements. These results do not support the idea
of the na\"ive power-law running of couplings in nonrenormalizable theories and
fail (with one exception) to reveal any simple closed formula for the leading
terms.Comment: LaTex, 11 page
Non-Relativistic Gravitation: From Newton to Einstein and Back
We present an improvement to the Classical Effective Theory approach to the
non-relativistic or Post-Newtonian approximation of General Relativity. The
"potential metric field" is decomposed through a temporal Kaluza-Klein ansatz
into three NRG-fields: a scalar identified with the Newtonian potential, a
3-vector corresponding to the gravito-magnetic vector potential and a 3-tensor.
The derivation of the Einstein-Infeld-Hoffmann Lagrangian simplifies such that
each term corresponds to a single Feynman diagram providing a clear physical
interpretation. Spin interactions are dominated by the exchange of the
gravito-magnetic field. Leading correction diagrams corresponding to the 3PN
correction to the spin-spin interaction and the 2.5PN correction to the
spin-orbit interaction are presented.Comment: 10 pages, 3 figures. v2: published version. v3: Added a computation
of Einstein-Infeld-Hoffmann in higher dimensions within our improved ClEFT
which partially confirms and partially corrects a previous computation. See
notes added at end of introductio
High Energy Field Theory in Truncated AdS Backgrounds
In this letter we show that, in five-dimensional anti-deSitter space (AdS)
truncated by boundary branes, effective field theory techniques are reliable at
high energy (much higher than the scale suggested by the Kaluza-Klein mass
gap), provided one computes suitable observables. We argue that in the model of
Randall and Sundrum for generating the weak scale from the AdS warp factor, the
high energy behavior of gauge fields can be calculated in a {\em cutoff
independent manner}, provided one restricts Green's functions to external
points on the Planck brane. Using the AdS/CFT correspondence, we calculate the
one-loop correction to the Planck brane gauge propagator due to charged bulk
fields. These effects give rise to non-universal logarithmic energy dependence
for a range of scales above the Kaluza-Klein gap.Comment: LaTeX, 7 pages; minor typos fixe
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