168 research outputs found
The Farrell-Jones isomorphism conjecture for 3-manifold groups
We show that the Fibered Isomorphism Conjecture (FIC) of Farrell and Jones
corresponding to the stable topological pseudoisotopy functor is true for the
fundamental groups of a large class of 3-manifolds. We also prove that if the
FIC is true for irreducible 3-manifold groups then it is true for all
3-manifold groups. In fact, this follows from a more general result we prove
here, namely we show that if the FIC is true for each vertex group of a graph
of groups with trivial edge groups then the FIC is true for the fundamental
group of the graph of groups. This result is part of a program to prove FIC for
the fundamental group of a graph of groups where all the vertex and edge groups
satisfy FIC. A consequence of the first result gives a partial solution to a
problem in the problem list of R. Kirby. We also deduce that the FIC is true
for a class of virtually PD_3-groups.
Another main aspect of this article is to prove the FIC for all Haken
3-manifold groups assuming that the FIC is true for B-groups. By definition a
B-group contains a finite index subgroup isomorphic to the fundamental group of
a compact irreducible 3-manifold with incompressible nonempty boundary so that
each boundary component is of genus \geq 2. We also prove the FIC for a large
class of B-groups and moreover, using a recent result of L.E. Jones we show
that the surjective part of the FIC is true for any B-group.Comment: 35 pages, 1 figure (.eps file), AMS Latex file, final version.
accepted for publication in K-theor
The structure of flame filaments in chaotic flows
The structure of flame filaments resulting from chaotic mixing within a
combustion reaction is considered. The transverse profile of the filaments is
investigated numerically and analytically based on a one-dimensional model that
represents the effect of stirring as a convergent flow. The dependence of the
steady solutions on the Damkohler number and Lewis number is treated in detail.
It is found that, below a critical Damkohler number Da(crit), the flame is
quenched by the flow. The quenching transition appears as a result of a
saddle-node bifurcation where the stable steady filament solution collides with
an unstable one. The shape of the steady solutions for the concentration and
temperature profiles changes with the Lewis number and the value of Da(crit)
increases monotonically with the Lewis number. Properties of the solutions are
studied analytically in the limit of large Damkohler number and for small and
large Lewis number.Comment: 17 pages, 13 figures, to be published in Physica
Zeta function method and repulsive Casimir forces for an unusual pair of plates at finite temperature
We apply the generalized zeta function method to compute the Casimir energy
and pressure between an unusual pair of parallel plates at finite temperature,
namely: a perfectly conducting plate and an infinitely permeable one. The high
and low temperature limits of these quantities are discussed; relationships
between high and low temperature limits are estabkished by means of a modified
version of the temperature inversion symmetry.Comment: latex file 9 pages, 3 figure
Quantum inequalities for the free Rarita-Schwinger fields in flat spacetime
Using the methods developed by Fewster and colleagues, we derive a quantum
inequality for the free massive spin- Rarita-Schwinger fields in
the four dimensional Minkowski spacetime. Our quantum inequality bound for the
Rarita-Schwinger fields is weaker, by a factor of 2, than that for the
spin- Dirac fields. This fact along with other quantum inequalities
obtained by various other authors for the fields of integer spin (bosonic
fields) using similar methods lead us to conjecture that, in the flat
spacetime, separately for bosonic and fermionic fields, the quantum inequality
bound gets weaker as the the number of degrees of freedom of the field
increases. A plausible physical reason might be that the more the number of
field degrees of freedom, the more freedom one has to create negative energy,
therefore, the weaker the quantum inequality bound.Comment: Revtex, 11 pages, to appear in PR
Stability of the lattice formed in first-order phase transitions to matter containing strangeness in protoneutron stars
Well into the deleptonization phase of a core collapse supernova, a
first-order phase transition to matter with macroscopic strangeness content is
assumed to occur and lead to a structured lattice defined by negatively charged
strange droplets. The lattice is shown to crystallize for expected droplet
charges and separations at temperatures typically obtained during the
protoneutronstar evolution. The melting curve of the lattice for small
spherical droplets is presented. The one-component plasma model proves to be an
adequate description for the lattice in its solid phase with deformation modes
freezing out around the melting temperature. The mechanical stability against
shear stresses is such that velocities predicted for convective phenomena and
differential rotation during the Kelvin-Helmholtz cooling phase might prevent
the crystallization of the phase transition lattice. A solid lattice might be
fractured by transient convection, which could result in anisotropic neutrino
transport. The melting curve of the lattice is relevant for the mechanical
evolution of the protoneutronstar and therefore should be included in future
hydrodynamics simulations.Comment: accepted for publication in Physical Review
The Quantum Interest Conjecture
Although quantum field theory allows local negative energy densities and
fluxes, it also places severe restrictions upon the magnitude and extent of the
negative energy. The restrictions take the form of quantum inequalities. These
inequalities imply that a pulse of negative energy must not only be followed by
a compensating pulse of positive energy, but that the temporal separation
between the pulses is inversely proportional to their amplitude. In an earlier
paper we conjectured that there is a further constraint upon a negative and
positive energy delta-function pulse pair. This conjecture (the quantum
interest conjecture) states that a positive energy pulse must overcompensate
the negative energy pulse by an amount which is a monotonically increasing
function of the pulse separation. In the present paper we prove the conjecture
for massless quantized scalar fields in two and four-dimensional flat
spacetime, and show that it is implied by the quantum inequalities.Comment: 17 pages, Latex, 3 figures, uses eps
Sex Disparities in Arrest Outcomes for Domestic Violence
Domestic violence arrests have been historically focused on protecting women and children from abusive men. Arrest patterns continue to reflect this bias with more men arrested for domestic violence compared to women. Such potential gender variations in arrest patterns pave the way to the investigation of disparities by sex of the offender in domestic violence arrests. This study utilizes data from a quantitative dataset that includes responses by police officers who completed a specially mandated checklist after responding to a domestic dispute. The results showed that while females are arrested quite often in domestic disputes, there remains a significant difference in the arrest outcome whereby male suspects were more likely to be arrested than female suspects. Regression models further indicated differences based on sex and certain predictors of arrest, which supported sex-based rationales in arrests for domestic violence.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles
We have made the first measurements of the virtual Compton scattering (VCS)
process via the H exclusive reaction in the nucleon resonance
region, at backward angles. Results are presented for the -dependence at
fixed GeV, and for the -dependence at fixed near 1.5 GeV.
The VCS data show resonant structures in the first and second resonance
regions. The observed -dependence is smooth. The measured ratio of
H to H cross sections emphasizes the different
sensitivity of these two reactions to the various nucleon resonances. Finally,
when compared to Real Compton Scattering (RCS) at high energy and large angles,
our VCS data at the highest (1.8-1.9 GeV) show a striking -
independence, which may suggest a transition to a perturbative scattering
mechanism at the quark level.Comment: 20 pages, 8 figures. To appear in Phys.Rev.
Protecting the environment through insect farming as a means to produce protein for use as livestock, poultry, and aquaculture feed
Securing protein for the approximate 10 billion humans expected to inhabit our planet by 2050 is a major priority for the global community. Evidence has accrued over the past 30 years that strongly supports and justifies the sustainable use of insects as a means to produce protein products as feed for pets, livestock, poultry, and aquacultured species. Researchers and entrepreneurs affiliated with universities and industries, respectively, from 18 nations distributed across North and South America, Europe, Asia, Africa and Australia contributed to the development of this article, which is an indication of the global interest on this topic. A brief overview of insects as feed for the aquaculture industry along with a review of the black soldier fly, Hermetia illucens (Diptera: Stratiomyidae), as a model for such systems is provided
Eficiência da absorção, translocação e uso de N e P pela Pfaffia glomerata (Spreng.) Pedersen
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