2,338 research outputs found
The stochastic background from cosmic (super)strings: popcorn and (Gaussian) continuous regimes
In the era of the next generation of gravitational wave experiments a
stochastic background from cusps of cosmic (super)strings is expected to be
probed and, if not detected, to be significantly constrained. A popcorn-like
background can be, for part of the parameter space, as pronounced as the
(Gaussian) continuous contribution from unresolved sources that overlap in
frequency and time. We study both contributions from unresolved cosmic string
cusps over a range of frequencies relevant to ground based interferometers,
such as LIGO/Virgo second generation (AdLV) and Einstein Telescope (ET) third
generation detectors, the space antenna LISA and Pulsar Timing Arrays (PTA). We
compute the sensitivity (at level) in the parameter space for AdLV,
ET, LISA and PTA. We conclude that the popcorn regime is complementary to the
continuous background. Its detection could therefore enhance confidence in a
stochastic background detection and possibly help determine fundamental string
parameters such as the string tension and the reconnection probability.Comment: 21 pages, 11 figures ; revised version after correction of a typo in
eq. 4.
Bargaining under incomplete information, fairness, and the hold-up problem
"In the hold-up problem incomplete contracts cause the proceeds of relationship-specific investments to be allocated by bargaining. This paper investigates the corresponding investment incentives if individuals have heterogeneous fairness preferences and thus differ in their bargaining behavior. Individual preferences are taken to be private information. Investments can then signal preferences and thereby influence beliefs and bargaining behavior. In consequence, individuals might choose high investments in order not to signal information that is unfavorable in the ensuing bargaining." [author's abstract
Elastic pion-nucleon scattering in chiral perturbation theory: A fresh look
Elastic pion-nucleon scattering is analyzed in the framework of chiral
perturbation theory up to fourth order within the heavy-baryon expansion and a
covariant approach based on an extended on-mass-shell renormalization scheme.
We discuss in detail the renormalization of the various low-energy constants
and provide explicit expressions for the relevant -functions and the
finite subtractions of the power-counting breaking terms within the covariant
formulation. To estimate the theoretical uncertainty from the truncation of the
chiral expansion, we employ an approach which has been successfully applied in
the most recent analysis of the nuclear forces. This allows us to reliably
extract the relevant low-energy constants from the available scattering data at
low energy. The obtained results provide a clear evidence that the breakdown
scale of the chiral expansion for this reaction is related to the
-resonance. The explicit inclusion of the leading contributions of the
-isobar is demonstrated to substantially increase the range of
applicability of the effective field theory. The resulting predictions for the
phase shifts are in an excellent agreement with the ones from the recent
Roy-Steiner-equation analysis of pion-nucleon scattering
Cosmic String Cusps with Small-Scale Structure: Their Forms and Gravitational Waveforms
We present a method for the introduction of small-scale structure into
strings constructed from products of rotation matrices. We use this method to
illustrate a range of possibilities for the shape of cusps that depends on the
properties of the small-scale structure. We further argue that the presence of
structure at cusps under most circumstances leads to the formation of loops at
the size of the smallest scales. On the other hand we show that the
gravitational waveform of a cusp remains generally unchanged; the primary
effect of small-scale structure is to smooth out the sharp waveform emitted in
the direction of cusp motion.Comment: RevTeX, 8 pages. Replaced with version accepted for publication by
PR
On the size of the smallest scales in cosmic string networks
We present a method for the calculation of the gravitational back reaction
cutoff on the smallest scales of cosmic string networks taking into account
that not all modes on strings interact with all other modes. This results in a
small scale structure cutoff that is sensitive to the initial spectrum of
perturbations present on strings. From a simple model, we compute the cutoffs
in radiation- and matter-dominated universes.Comment: 4 pages, revte
Equal sharing rules in partnerships
Partnerships are the prevalent organizational form in many industries. Profits are most frequently shared equally among the partners. The purpose of our paper is to provide a rationale for equal sharing rules. We show that with inequity averse partners the equal sharing rule is the unique sharing rule that maximizes the partners' incentives to exert effort. We further show that inequity aversion can enhance efficiency in partnerships of given size, but that it can also cause partnerships to be inefficiently small
Thomas-Fermi Approximation for a Condensate with Higher-order Interactions
We consider the ground state of a harmonically trapped Bose-Einstein
condensate within the Gross-Pitaevskii theory including the effective-range
corrections for a two-body zero-range potential. The resulting non-linear
Schr\"odinger equation is solved analytically in the Thomas-Fermi approximation
neglecting the kinetic energy term. We present results for the chemical
potential and the condensate profiles, discuss boundary conditions, and compare
to the usual Thomas-Fermi approach. We discuss several ways to increase the
influence of effective-range corrections in experiment with magnetically
tunable interactions. The level of tuning required could be inside experimental
reach in the near future.Comment: 8 pages, RevTex4 format, 5 figure
Gravitational wave bursts from cosmic (super)strings: Quantitative analysis and constraints
We discuss data analysis techniques that can be used in the search for
gravitational wave bursts from cosmic strings. When data from multiple
interferometers are available, we describe consistency checks that can be used
to greatly reduce the false alarm rates. We construct an expression for the
rate of bursts for arbitrary cosmic string loop distributions and apply it to
simple known solutions. The cosmology is solved exactly and includes the
effects of a late-time acceleration. We find substantially lower burst rates
than previous estimates suggest and explain the disagreement. Initial LIGO is
unlikely to detect field theoretic cosmic strings with the usual loop sizes,
though it may detect cosmic superstrings as well as cosmic strings and
superstrings with non-standard loop sizes (which may be more realistic). In the
absence of a detection, we show how to set upper limits based on the loudest
event. Using Initial LIGO sensitivity curves, we show that these upper limits
may result in interesting constraints on the parameter space of theories that
lead to the production of cosmic strings.Comment: Replaced with version accepted for publication in PR
- …