131 research outputs found
Creation of a brane world with Gauss-Bonnet term
We study a creation of a brane world using an instanton solution. We analyze
a brane model with a Gauss-Bonnet term in a bulk spacetime. The curvature of
3-brane is assumed to be closed, flat, or open. We construct instanton
solutions with branes for those models, and calculate the value of the actions
to discuss an initial state of a brane universe.Comment: 9 pages, 10 figure
Emergent spatial correlations in stochastically evolving populations
We study the spatial pattern formation and emerging long range correlations
in a model of three species coevolving in space and time according to
stochastic contact rules. Analytical results for the pair correlation
functions, based on a truncation approximation and supported by computer
simulations, reveal emergent strategies of survival for minority agents based
on selection of patterns. Minority agents exhibit defensive clustering and
cooperative behavior close to phase transitions.Comment: 11 pages, 4 figures, Adobe PDF forma
Junction Conditions of Friedmann-Robertson-Walker Space-Times
We complete a classification of junctions of two Friedmann-Robertson-Walker
space-times bounded by a spherical thin wall. Our analysis covers super-horizon
bubbles and thus complements the previous work of Berezin, Kuzumin and Tkachev.
Contrary to sub-horizon bubbles, various topology types for super-horizon
bubbles are possible, regardless of the sign of the extrinsic curvature. We
also derive a formula for the peculiar velocity of a domain wall for all types
of junction.Comment: 7 pages, LaTeX, figures are not included (available on request by
regular mail), WU-AP/31/9
Natural dimethyl sulfide gradients would lead marine predators to higher prey biomass
© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Owen, K., Saeki, K., Warren, J. D., Bocconcelli, A., Wiley, D. N., Ohira, S., Bombosch, A., Toda, K., & Zitterbart, D. P. Natural dimethyl sulfide gradients would lead marine predators to higher prey biomass. Communications Biology, 4(1), (2021): 149, https://doi.org/10.1038/s42003-021-01668-3.Finding prey is essential to survival, with marine predators hypothesised to track chemicals such as dimethyl sulfide (DMS) while foraging. Many predators are attracted to artificially released DMS, and laboratory experiments have shown that zooplankton grazing on phytoplankton accelerates DMS release. However, whether natural DMS concentrations are useful for predators and correlated to areas of high prey biomass remains a fundamental knowledge gap. Here, we used concurrent hydroacoustic surveys and in situ DMS measurements to present evidence that zooplankton biomass is spatially correlated to natural DMS concentration in air and seawater. Using agent simulations, we also show that following gradients of DMS would lead zooplankton predators to areas of higher prey biomass than swimming randomly. Further understanding of the conditions and scales over which these gradients occur, and how they are used by predators, is essential to predicting the impact of future changes in the ocean on predator foraging success.Open Access funding enabled and organized by Projekt DEAL.
This study was funded by the Herrington Fitch Family Foundation, by the Woods Hole Oceanographic Institution Joint Initiative Awards Fund from the Andrew W. Mellon Foundation and The President’s Investment Fund, and by KAKENHI, Grants-in-Aid for Basic Research (B) (Grant no. 16H04168) and Bilateral Programs Joint Research Projects (open partnership), both from the Japan Society for the Promotion of Science. The authors thank Mrs. Norio Hayashi, Takanori Nagahata, and Ms. Mihoko Asano (Mitsubishi Chemical Analytech Co.) for their support with the SGV-CL device. The research was conducted under Scientific Research Permit number 18059, issued by the National Oceanic and Atmospheric Administration under the Marine Mammal Protection Act
Monopole Inflation in Brans-Dicke Theory
According to previous work, topological defects expand exponentially without
an end if the vacuum expectation value of the Higgs field is of the order of
the Planck mass. We extend the study of inflating topological defects to the
Brans-Dicke gravity. With the help of numerical simulation we investigate the
dynamics and spacetime structure of a global monopole. Contrary to the case of
the Einstein gravity, any inflating monopole eventually shrinks and takes a
stable configuration. We also discuss cosmological constraints on the model
parameters.Comment: 17 pages, revtex, including figures, discussions in more general
theories are added, to appear in Phys. Rev.
The Einstein Equations on the 3-Brane World
We carefully investigate the gravitational equations of the brane world, in
which all the matter forces except gravity are confined on the 3-brane in a
5-dimensional spacetime with symmetry.
We derive the effective gravitational equations on the brane, which reduce to
the conventional Einstein equations in the low energy limit. {}From our general
argument we conclude that the first Randall & Sundrum-type theory (RS1)
[hep-ph/9905221] predicts that the brane with the negative tension is an
anti-gravity world and hence should be excluded from the physical point of
view. Their second-type theory (RS2) [hep-th/9906064] where the brane has the
positive tension provides the correct signature of gravity. In this latter
case, if the bulk spacetime is exactly anti-de Sitter, generically the matter
on the brane is required to be spatially homogeneous because of the Bianchi
identities. By allowing deviations from anti-de Sitter in the bulk, the
situation will be relaxed and the Bianchi identities give just the relation
between the Weyl tensor and the energy momentum tensor. In the present brane
world scenario, the effective Einstein equations cease to be valid during an
era when the cosmological constant on the brane is not well-defined, such as in
the case of the matter dominated by the potential energy of the scalar field.Comment: 8 pages, references adde
Dynamics of Void and its Shape in Redshift Space
We investigate the dynamics of a single spherical void embedded in a
Friedmann-Lema\^itre universe, and analyze the void shape in the redshift
space. We find that the void in the redshift space appears as an ellipse shape
elongated in the direction of the line of sight (i.e., an opposite deformation
to the Kaiser effect). Applying this result to observed void candidates at the
redshift z~1-2, it may provide us with a new method to evaluate the
cosmological parameters, in particular the value of a cosmological constant.Comment: 19 pages, 11 figure
Glueball mass from quantized knot solitons and gauge-invariant gluon mass
We propose an approach which enables one to obtain simultaneously the
glueball mass and the gluon mass in the gauge-invariant way to shed new light
on the mass gap problem in Yang-Mills theory. First, we point out that the
Faddeev (Skyrme--Faddeev-Niemi) model can be induced through the
gauge-invariant vacuum condensate of mass dimension two from SU(2) Yang-Mills
theory. Second, we obtain the glueball mass spectrum by performing the
collective coordinate quantization of the topological knot soliton in the
Faddeev model. Third, we demonstrate that a relationship between the glueball
mass and the gluon mass is obtained, since the gauge-invariant gluon mass is
also induced from the relevant vacuum condensate. Finally, we determine
physical values of two parameters in the Faddeev model and give an estimate of
the relevant vacuum condensation in Yang-Mills theory. Our results indicate
that the Faddeev model can play the role of a low-energy effective theory of
the quantum SU(2) Yang-Mills theory.Comment: 17 pages, 2 figures, 3 tables; a version accepted for publication in
J. Phys. A: Math. Gen.; Sect. 2 and sect. 5 (old sect. 4) are modified. Sect.
4, Tables 1 and Table 3 are adde
Two Boosted Black Holes in Asymptotically de Sitter Space-Time - Relation between Mass and Apparent Horizon Formation -
We study the apparent horizon for two boosted black holes in the
asymptotically de Sitter space-time by solving the initial data on a space with
punctures. We show that the apparent horizon enclosing both black holes is not
formed if the conserved mass of the system (Abbott-Deser mass) is larger than a
critical mass. The black hole with too large AD mass therefore cannot be formed
in the asymptotically de Sitter space-time even though each black hole has any
inward momentum. We also discuss the dynamical meaning of AD mass by examining
the electric part of the Weyl tensor (the tidal force) for various initial
data.Comment: 15 pages, accepted for publication in PR
Gravitational waves from a test particle scattered by a neutron star: Axial mode case
Using a metric perturbation method, we study gravitational waves from a test
particle scattered by a spherically symmetric relativistic star. We calculate
the energy spectrum and the waveform of gravitational waves for axial modes.
Since metric perturbations in axial modes do not couple to the matter fluid of
the star, emitted waves for a normal neutron star show only one peak in the
spectrum, which corresponds to the orbital frequency at the turning point,
where the gravitational field is strongest. However, for an ultracompact star
(the radius ), another type of resonant periodic peak appears in
the spectrum. This is just because of an excitation by a scattered particle of
axial quasinormal modes, which were found by Chandrasekhar and Ferrari. This
excitation comes from the existence of the potential minimum inside of a star.
We also find for an ultracompact star many small periodic peaks at the
frequency region beyond the maximum of the potential, which would be due to a
resonance of two waves reflected by two potential barriers (Regge-Wheeler type
and one at the center of the star). Such resonant peaks appear neither for a
normal neutron star nor for a Schwarzschild black hole. Consequently, even if
we analyze the energy spectrum of gravitational waves only for axial modes, it
would be possible to distinguish between an ultracompact star and a normal
neutron star (or a Schwarzschild black hole).Comment: 21 pages, revtex, 11 figures are attached with eps files Accepted to
Phys. Rev.
- …