14,193 research outputs found
Path Integral and the Induction Law
We show how the induction law is correctly used in the path integral
computation of the free particle propagator. The way this primary path integral
example is treated in most textbooks is a little bit missleading.Comment: 5 latex pages, no figure
Study of sequential semileptonic decays of b hadrons produced at the Tevatron
We present a study of rates and kinematical properties of lepton pairs
contained in central jets with transverse energy E_T > 15 GeV that are produced
at the Fermilab Tevatron collider. We compare the data to a QCD prediction
based on the HERWIG and QQ Monte Carlo generator programs.We find that the data
are poorly described by the simulation, in which sequential semileptonic decays
of single b quarks (b --> l c X with c --> l s X) are the major source of such
lepton pairs.Comment: 25 pages, 8 figures. Some typos were fixed in the text and
bibliography. Submitted to Phys. Rev.
Phenomenological study of the atypical heavy flavor production observed at the Fermilab Tevatron
We address known discrepancies between the heavy flavor properties of jets
produced at the Tevatron collider and the prediction of conventional-QCD
simulations. In this study, we entertain the possibility that these effects are
real and due to new physics. We show that all anomalies can be simultaneously
fitted by postulating the additional pair production of light bottom squarks
with a 100% semileptonic branching fraction.Comment: 30 pages, 13 figures, 3 tables. Submitted to Phys. Rev.
N-particle sector of quantum field theory as a quantum open system
We give an exposition of a technique, based on the Zwanzig projection
formalism, to construct the evolution equation for the reduced density matrix
corresponding to the n-particle sector of a field theory. We consider the case
of a scalar field with a interaction as an example and construct the
master equation at the lowest non-zero order in perturbation theory.Comment: 12 pages, Late
Diffractive photoproduction of opposite-charge pseudoscalar meson pairs at high energies
We calculate the cross section for diffractive photoproduction of
opposite-charge pseudoscalar meson pairs , ,
and in a broad range of center-of-mass energies relevant
for GlueX/Hall D, FOCUS, COMPASS and HERA experiments. In the case of
production we find that the interference of the resonance
and the two-pion continuum leads to a considerable deformation of the shape of
in agreement with the data from the ZEUS collaboration. We also
discuss the spectral shape of the as a function of the momentum
transfer and the contribution of higher partial waves to the mass
spectrum. We predict a sizeable energy-dependent forward-backward asymmetry in
the Gottfried-Jackson frame. For the heavy meson production we find that the
cross section for diffractive production increases much slower than the one for
open charm or bottom production. We discuss lower and upper limits for the
cross sections for diffractive production of and pairs,
which we find can be as large as 10% of the open flavor production.Comment: 14 pages, 19 figure
Gut microbiome–micronutrient interaction: The key to controlling the bioavailability of minerals and vitamins?
Micronutrients, namely, vitamins and minerals, are necessary for the proper functioning of the human body, and their deficiencies can have dramatic short- and long-term health consequences. Among the underlying causes, certainly a reduced dietary intake and/or poor absorption in the gastrointestinal tract play a key role in decreasing their bioavailability. Recent evidence from clinical and in vivo studies suggests an increasingly important contribution from the gut microbiome. Commensal microorganisms can in fact regulate the levels of micronutrients, both by intervening in the biosynthetic processes and by modulating their absorption. This short narrative review addresses the pivotal role of the gut microbiome in influencing the bioavailability of vitamins (such as A, B, C, D, E, and K) and minerals (calcium, iron, zinc, magnesium, and phosphorous), as well as the impact of these micronutrients on microbiome composition and functionality. Personalized microbiome-based intervention strategies could therefore constitute an innovative tool to counteract micronutrient deficiencies by modulating the gut microbiome toward an eubiotic configuration capable of satisfying the needs of our organism, while promoting general health
Vacuum energies due to delta-like currents: simulating classical objects along branes with arbitrary codimensions
In this paper we investigate the vacuum energies of several models of quantum
fields interacting with static external currents (linear couplings)
concentrated along parallel branes with an arbitrary number of codimensions. We
show that we can simulate the presence of static charges distributions as well
as the presence of classical static dipoles in any dimension for massive and
massless fields. We also show that we can produce confining potentials with
massless self interacting scalar fields as well as long range anisotropic
potentials.Comment: 18 latex page
Long Josephson Tunnel Junctions with Doubly Connected Electrodes
In order to mimic the phase changes in the primordial Big Bang, several
"cosmological" solid-state experiments have been conceived, during the last
decade, to investigate the spontaneous symmetry breaking in superconductors and
superfluids cooled through their transition temperature. In one of such
experiments the number of magnetic flux quanta spontaneously trapped in a
superconducting loop was measured by means of a long Josephson tunnel junction
built on top of the loop itself. We have analyzed this system and found a
number of interesting features not occurring in the conventional case with
simply connected electrodes. In particular, the fluxoid quantization results in
a frustration of the Josephson phase, which, in turn, reduces the junction
critical current. Further, the possible stable states of the system are
obtained by a self-consistent application of the principle of minimum energy.Comment: 34 pages, 9 figures, Phys. Rev. B April 201
Control of Multi-level Voltage States in a Hysteretic SQUID Ring-Resonator System
In this paper we study numerical solutions to the quasi-classical equations
of motion for a SQUID ring-radio frequency (rf) resonator system in the regime
where the ring is highly hysteretic. In line with experiment, we show that for
a suitable choice of of ring circuit parameters the solutions to these
equations of motion comprise sets of levels in the rf voltage-current dynamics
of the coupled system. We further demonstrate that transitions, both up and
down, between these levels can be controlled by voltage pulses applied to the
system, thus opening up the possibility of high order (e.g. 10 state),
multi-level logic and memory.Comment: 8 pages, 9 figure
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