106 research outputs found
On the Dynamical Capture of a MSP by an IMBH in a Globular Cluster
Globular clusters (GCs) are rich of millisecond pulsars (MSPs) and might also host single or binary intermediate-mass black holes (IMBHs). We simulate 3- and 4-body encounters in order to test the possibility that an IMBH captures a MSP. The newly formed system could be revealed from the timing signal of the MSP, providing an unambiguous measure of the BH mass. In current surveys, the number of expected [IMBH,MSP] binaries in the Milky Way is ~0.1. If next-generation radio telescopes (e.g. SKA) will detect ~10 times more MSPs in GCs, we expect to observe at least one [IMBH,MSP] binar
Millisecond pulsars around intermediate-mass black holes in globular clusters
Globular clusters (GCs) are expected to be breeding grounds for the formation of single or binary intermediate-mass black holes (IMBHs) of âł100 Mâ, but a clear signature of their existence is still missing. In this context, we study the process of dynamical capture of a millisecond pulsar (MSP) by a single or binary IMBH, simulating various types of single-binary and binary-binary encounters. It is found that [IMBH, MSP] binaries form over cosmic time in a cluster, at rates âČ10â11 yrâ1, via encounters of wide-orbit binary MSPs off the single IMBH, and at a lower pace, via interactions of (binary or single) MSPs with the IMBH orbited by a typical cluster star. The formation of an [IMBH, MSP] system is strongly inhibited if the IMBH is orbited by a stellar mass black hole (BH): in this case, the only viable path is through the formation of a rare stable hierarchical triplet with the MSP orbiting exterior to the [IMBH, BH] binary. The [IMBH, MSP] binaries that form are relatively short-lived, âČ108â109 yr, since their orbits decay via emission of gravitational waves. The detection of an [IMBH, MSP] system has a low probability of occurrence, when inferred from the current sample of MSPs in GCs. If next-generation radio telescopes, like Square Kilometre Array (SKA), will detect an order of magnitude larger population of MSP in GCs, at least one [IMBH, MSP] is expected. Therefore, a complete search for low-luminosity MSPs in the GCs of the Milky Way with SKA will have the potential of testing the hypothesis that IMBHs of the order of 100 Mâ are commonly hosted in GCs. The discovery will unambiguously prove that BHs exist in the still uncharted interval of masses around âł100 M
The dynamical fingerprint of intermediate mass black holes in globular clusters
A number of observations hints for the presence of an intermediate mass black
hole (IMBH) in the core of three globular clusters: M15 and NGC 6752 in the
Milky Way, and G1, in M31. However the existence of these IMBHs is far form
being conclusive. In this paper, we review their main formation channels and
explore possible observational signs that a single or binary IMBH can imprint
on cluster stars. In particular we explore the role played by a binary IMBH in
transferring angular momentum and energy to stars flying by.Comment: 8 pages,6 figures,Invited review in: "Interacting binaries", July
4-10 Cefalu, eds. Antonelli et al., to be published with AI
The initial conditions of observed star clusters - I. Method description and validation
We have coupled a fast, parametrized star cluster evolution code to a Markov
Chain Monte Carlo code to determine the distribution of probable initial
conditions of observed star clusters, which may serve as a starting point for
future -body calculations. In this paper we validate our method by applying
it to a set of star clusters which have been studied in detail numerically with
-body simulations and Monte Carlo methods: the Galactic globular clusters
M4, 47 Tucanae, NGC 6397, M22, Centauri, Palomar 14 and Palomar 4, the
Galactic open cluster M67, and the M31 globular cluster G1. For each cluster we
derive a distribution of initial conditions that, after evolution up to the
cluster's current age, evolves to the currently observed conditions. We find
that there is a connection between the morphology of the distribution of
initial conditions and the dynamical age of a cluster and that a degeneracy in
the initial half-mass radius towards small radii is present for clusters which
have undergone a core collapse during their evolution. We find that the results
of our method are in agreement with -body and Monte Carlo studies for the
majority of clusters. We conclude that our method is able to find reliable
posteriors for the determined initial mass and half-mass radius for observed
star clusters, and thus forms an suitable starting point for modeling an
observed cluster\rq{}s evolution.Comment: 39 pages, 28 figures, accepted for publication in MNRA
Are neuromuscular adaptations present in people with recurrent spinal pain during a period of remission?:A protocol for a systematic review
Poincare Invariance of a Quantized Duality Symmetric Theory
The noncovariant duality symmetric action put forward by Schwarz-Sen is
quantized by means of the Dirac bracket quantization procedure. The resulting
quantum theory is shown to be, nevertheless, relativistically invariant
Gravitational-wave memory revisited: memory from the merger and recoil of binary black holes
Gravitational-wave memory refers to the permanent displacement of the test
masses in an idealized (freely-falling) gravitational-wave interferometer.
Inspiraling binaries produce a particularly interesting form of memory--the
Christodoulou memory. Although it originates from nonlinear interactions at 2.5
post-Newtonian order, the Christodoulou memory affects the gravitational-wave
amplitude at leading (Newtonian) order. Previous calculations have computed
this non-oscillatory amplitude correction during the inspiral phase of binary
coalescence. Using an "effective-one-body" description calibrated with the
results of numerical relativity simulations, the evolution of the memory during
the inspiral, merger, and ringdown phases, as well as the memory's final
saturation value, are calculated. Using this model for the memory, the
prospects for its detection are examined, particularly for supermassive black
hole binary coalescences that LISA will detect with high signal-to-noise
ratios. Coalescing binary black holes also experience center-of-mass recoil due
to the anisotropic emission of gravitational radiation. These recoils can
manifest themselves in the gravitational-wave signal in the form of a "linear"
memory and a Doppler shift of the quasi-normal-mode frequencies. The prospects
for observing these effects are also discussed.Comment: 6 pages, 2 figures; accepted to the proceedings of the 7th
International LISA Symposium; v2: updated figures and signal-to-noise ratios,
several minor changes to the tex
Pasti-Sorokin-Tonin Actions in the Presence of Sources
Pasti, Sorokin and Tonin have recently constructed manifestly
Lorentz-invariant actions for self-dual field strengths and for Maxwell fields
with manifest electromagnetic duality. Using the method of Deser, Gomberoff,
Henneaux and Teitelboim, we generalize these actions in the presence of
sources.Comment: 6 pages, LaTe
Irreversible Processes in Inflationary Cosmological Models
By using the thermodynamic theory of irreversible processes and Einstein
general relativity, a cosmological model is proposed where the early universe
is considered as a mixture of a scalar field with a matter field. The scalar
field refers to the inflaton while the matter field to the classical particles.
The irreversibility is related to a particle production process at the expense
of the gravitational energy and of the inflaton energy. The particle production
process is represented by a non-equilibrium pressure in the energy-momentum
tensor. The non-equilibrium pressure is proportional to the Hubble parameter
and its proportionality factor is identified with the coefficient of bulk
viscosity. The dynamic equations of the inflaton and the Einstein field
equations determine the time evolution of the cosmic scale factor, the Hubble
parameter, the acceleration and of the energy densities of the inflaton and
matter. Among other results it is shown that in some regimes the acceleration
is positive which simulates an inflation. Moreover, the acceleration decreases
and tends to zero in the instant of time where the energy density of matter
attains its maximum value.Comment: 13 pages, 2 figures, to appear in PR
Covariant path integral for chiral p-forms
The covariant path integral for chiral bosons obtained by McClain, Wu and Yu
is generalized to chiral p-forms. In order to handle the reducibility of the
gauge transformations associated with the chiral p-forms and with the new
variables (in infinite number) that must be added to eliminate the second class
constraints, the field-antifield formalism is used.Comment: revtex, 9 pages, submitted to Physical Review
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