1,839 research outputs found
Perturbation theory for a stochastic process with Ornstein-Uhlenbeck noise
The Ornstein-Uhlenbeck process may be used to generate a noise signal with a
finite correlation time. If a one-dimensional stochastic process is driven by
such a noise source, it may be analysed by solving a Fokker-Planck equation in
two dimensions. In the case of motion in the vicinity of an attractive fixed
point, it is shown how the solution of this equation can be developed as a
power series. The coefficients are determined exactly by using algebraic
properties of a system of annihilation and creation operators.Comment: 7 pages, 0 figure
The Influence of World-Sheet Boundaries on Critical Closed String Theory
This paper considers interactions between closed strings and open strings
satisfying either Neumann or constant (point-like) Dirichlet boundary
conditions in a BRST formalism in the critical dimension. With Neumann
conditions this reproduces the well-known stringy version of the Higgs
mechanism. With Dirichlet conditions the open-string states correspond to
either auxiliary or Lagrange multiplier target-space fields and their coupling
to the closed-string sector leads to constraints on the closed-string spectrum.Comment: 15 pages, QMW-92-18;NI9201
Symmetry Breaking at enhanced Symmetry Points
The influence of world-sheet boundary condensates on the toroidal
compactification of bosonic string theories is considered. At the special
points in the moduli space at which the closed-string theory possesses an
enhanced unbroken symmetry (where is a semi-simple product of
simply laced groups) a scalar boundary condensate parameterizes the coset
. Fluctuations around this background define an open-string
generalization of the corresponding chiral nonlinear sigma model. Tree-level
scattering amplitudes of on-shell massless states (\lq pions') reduce to the
amplitudes of the principal chiral model for the group in the low energy
limit. Furthermore, the condition for the vanishing of the renormalization
group beta function at one loop results in the familiar equation of motion for
that model. The quantum corrections to the open-string theory generate a mixing
of open and closed strings so that the coset-space pions mix with the
closed-string gauge fields, resulting in a Higgs-like breakdown of
the symmetry to the diagonal group. The case of non-oriented strings is
also discussed.Comment: 32 pages, LaTeX, 2 figures in uuencoded fil
The Intersection of Diabetes and Cardiovascular Disease—A Focus on New Therapies
Diabetes is a leading cause of cardiovascular disease and its associated morbidity. While the medical community has had access to numerous glucose lowering therapies over the last decades, it was not until recently that newer agents demonstrated improvement in cardiovascular outcomes. In particular, diabetes care and management of its attendant cardiovascular risk is now being revolutionized with the development and provision of the SGLT-2 inhibitors and GLP1-receptor agonists. Given the exciting data with these new classes of diabetes therapeutics, there is a clear need to improve education and utilization of these evidence-based medications across a wide spectrum of clinicians, including cardiologists. The aim of this review is to familiarize the cardiovascular specialist with the benefits and harms of the most commonly used oral anti- hyperglycemic medications, with an emphasis on SGLT-2 inhibitors and GLP-1 receptor agonists
EC02-179 Managing Livestock Manure to Protect Environmental Quality
This book covers the land application part of manure management. With increasing regulations, the livestock producer needs to understand the scientific principles that affect manure transformations and how to use these principles to manage the manure for maximum fertilizer value with minimal environmental impact. Improved land application of manure is one part of the solution, but we suggest that the producer evaluate the quantity of nutrients arriving on the farm as feed, animals, and fertilizer compared to the total that is exported. Achieving a nutrient balance will reduce potential environmental hazards often associated with animal agriculture
The Zel'dovich effect and evolution of atomic Rydberg spectra along the Periodic Table
In 1959 Ya. B. Zel'dovich predicted that the bound-state spectrum of the
non-relativistic Coulomb problem distorted at small distances by a short-range
potential undergoes a peculiar reconstruction whenever this potential alone
supports a low-energy scattering resonance. However documented experimental
evidence of this effect has been lacking. Previous theoretical studies of this
phenomenon were confined to the regime where the range of the short-ranged
potential is much smaller than Bohr's radius of the Coulomb field. We go beyond
this limitation by restricting ourselves to highly-excited s states. This
allows us to demonstrate that along the Periodic Table of elements the
Zel'dovich effect manifests itself as systematic periodic variation of the
Rydberg spectra with a period proportional to the cubic root of the atomic
number. This dependence, which is supported by analysis of experimental and
numerical data, has its origin in the binding properties of the ionic core of
the atom.Comment: 17 pages, 12 figure
Black-Hole Spin Dependence in the Light Curves of Tidal Disruption Events
A star orbiting a supermassive black hole can be tidally disrupted if the
black hole's gravitational tidal field exceeds the star's self gravity at
pericenter. Some of this stellar tidal debris can become gravitationally bound
to the black hole, leading to a bright electromagnetic flare with bolometric
luminosity proportional to the rate at which material falls back to pericenter.
In the Newtonian limit, this flare will have a light curve that scales as
t^-5/3 if the tidal debris has a flat distribution in binding energy. We
investigate the time dependence of the black-hole mass accretion rate when
tidal disruption occurs close enough the black hole that relativistic effects
are significant. We find that for orbits with pericenters comparable to the
radius of the marginally bound circular orbit, relativistic effects can double
the peak accretion rate and halve the time it takes to reach this peak
accretion rate. The accretion rate depends on both the magnitude of the
black-hole spin and its orientation with respect to the stellar orbit; for
orbits with a given pericenter radius in Boyer-Lindquist coordinates, a maximal
black-hole spin anti-aligned with the orbital angular momentum leads to the
largest peak accretion rate.Comment: 16 pages, 15 figures, 1 table, PRD published versio
Entanglement and Timing-Based Mechanisms in the Coherent Control of Scattering Processes
The coherent control of scattering processes is considered, with electron
impact dissociation of H used as an example. The physical mechanism
underlying coherently controlled stationary state scattering is exposed by
analyzing a control scenario that relies on previously established entanglement
requirements between the scattering partners. Specifically, initial state
entanglement assures that all collisions in the scattering volume yield the
desirable scattering configuration. Scattering is controlled by preparing the
particular internal state wave function that leads to the favored collisional
configuration in the collision volume. This insight allows coherent control to
be extended to the case of time-dependent scattering. Specifically, we identify
reactive scattering scenarios using incident wave packets of translational
motion where coherent control is operational and initial state entanglement is
unnecessary. Both the stationary and time-dependent scenarios incorporate
extended coherence features, making them physically distinct. From a
theoretical point of view, this work represents a large step forward in the
qualitative understanding of coherently controlled reactive scattering. From an
experimental viewpoint, it offers an alternative to entanglement-based control
schemes. However, both methods present significant challenges to existing
experimental technologies
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