212 research outputs found
Canonical Quantization of the Maxwell-Chern-Simons Theory in the Coulomb Gauge
The Maxwell-Chern-Simons theory is canonically quantized in the Coulomb gauge
by using the Dirac bracket quantization procedure. The determination of the
Coulomb gauge polarization vector turns out to be intrincate. A set of quantum
Poincar\'e densities obeying the Dirac-Schwinger algebra, and, therefore, free
of anomalies, is constructed. The peculiar analytical structure of the
polarization vector is shown to be at the root for the existence of spin of the
massive gauge quanta.The Coulomb gauge Feynman rules are used to compute the
M\"oller scattering amplitude in the lowest order of perturbation theory. The
result coincides with that obtained by using covariant Feynman rules. This
proof of equivalence is, afterwards, extended to all orders of perturbation
theory. The so called infrared safe photon propagator emerges as an effective
propagator which allows for replacing all the terms in the interaction
Hamiltonian of the Coulomb gauge by the standard field-current minimal
interaction Hamiltonian.Comment: 21 pages, typeset in REVTEX, figures not include
A MULTIDISCIPLINARY DOCUMENTAL REPRESENTATION METHOD FOR KINETIC AND ENVIRONMENTAL ART
Abstract. The contribution addresses the definition of a new collaborative documental method for designing and managing the different phases of conservation of kinetic-programmed art. Our approach consists of developing a new representative model that includes both mechanical parts and spatial characteristics. The research stems from a specific case-study, Ambiente â Strutturazione a parametri virtuali (1969) by Gabriele Devecchi, permanently displayed at Museo del '900 in Milan since 2010. Starting from the dimensional and technical data, we obtained a graphical model of lamps 2D and 3D. They were enriched by a detailed abacus describing all the elements and by specific maps capturing all the phases of regular and extraordinary maintenance underwent by the environment. The second part was carried out with a report about physical motion. The goal has been representing speed and geometry of the movement inside the space. By merging the first part of the documenting process and the second one we've got a graphic digital model including information about the individual parts of the installation and their mechanical interaction. The third and last step is ongoing and tackles the challenge of using virtual technologies for the description of the whole environment. Thanks to a collaboration between technicians and theoretic scholars, we attempted to match the study of the physical motion and all data about the structural parts with the careful consideration of historical-artistic and perception-related features. The work led to the conclusion that a virtual, immersive reproduction of the environment is not enough for deeply understanding the experience enjoyed by users inside it, because it misses the embodied perception activated by the artwork. For this reason, this study may be considered as a step in a broader research path about documentation of complex environmental, immersive, kinetic works of art.</p
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
On the Interacting Chiral Gauge Field Theory in D=6 and the Off-Shell Equivalence of Dual Born-Infeld-Like Actions
A canonical action describing the interaction of chiral gauge fields in D=6
Minkowski space-time is constructed. In a particular partial gauge fixing it
reduces to the action found by Perry and Schwarz. The additional gauge
symmetries are used to show the off-shell equivalence of the dimensional
reduction to D=5 Minkowski space-time of the chiral gauge field canonical
action and the Born-Infeld canonical action describing an interacting D=5
Abelian vector field. Its extension to improve the on-shell equivalence
arguments of dual D-brane actions to off-shell ones is discussed.Comment: 18 page
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
Regolith mining in Shackleton Crater: Propellant, building materials and vital resources production for a long duration manned mission
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
A solution to the zero-hamiltonian problem in 2-D gravity
The zero-hamiltonian problem, present in reparametrization invariant systems,
is solved for the 2-D induced gravity model. Working with methods developed by
Henneaux et al. we find systematically the reduced phase-space physics,
generated by an {\it effective} hamiltonian obtained after complete gauge
fixing.Comment: 5 pages, revte
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
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