119858324
Anyons from bosons
Abstract We consider systems containing two or more distinct species of particles in two spatial dimensions. In quantizations of these systems, the statistics of composites containing more than one type of particle are not completely determined by the statistics of the constituents. In particular there exist quantum theories in which two bosons can combine to form an anyon with any desired statistical angle. We demonstrate these results using the topological approach to quantum kinematics, which in this case leads to a generalization of ordinary braid theory in two dimensions. Comparisons are made to three-dimensional systems.
119546147
Knots and links of nonabelian string
Abstract We consider a class of closed stringlike configurations, called essentially knotted , which occur in certain (3 + 1)-dimensional Yang-Mills-Higgs theories where a compact gauge group G breaks to a finite, nonabelian subgroup H. Such objects are labelled by more than one flux element in H, and cannot be deformed into the vacuum without overlapping the cores of two segments of string carrying noncommuting fluxes. Analogous results for multicomponent links of string are also given. Our analysis is performed within a general topological framework for discussing the knotting and linking of strings in spontaneously broken gauge theories.
14856505
Weak-field gravity of circular cosmic strings.
A weak-field solution of Einstein's equations is constructed. It is generated by a circular cosmic string externally supported against collapse. The solution exhibits a conical singularity, and the corresponding deficit angle is the same as for a straight string for the same linear energy density. This confirms the deficit-angle assumption made in the Frolov-Israel-Unruh derivation of the metric describing a string loop at a moment of time symmetry.
14821200
RINGS AND BALLS
We examine the various linkings in space-time of “ball-like” and “ring-like” topological solitons in certain nonlinear sigma models in 2+1 and 3+1 dimensions. By going to theories where soliton overlaps are forbidden, these linkings become homotopically nontrivial and can be studied by investigating the topology of the corresponding configuration spaces. Our analysis reveals the existence of topological terms which give the linking number of the world tubes of distinct species of ball solitons in 2+1 dimensions, or which in 3+1 dimensions count the number of times a ball or ring soliton threads through the center of a ring of a different species. We explicitly construct these terms for our models, and generalize them to cases where soliton overlaps are no longer strictly forbidden so the terms are no longer purely topological. One of the (3+1)-dimensional theories we consider also has topological solitons which consist of two rings (of distinct species) linked in space.
117648248
Topics in Particle Physics
1891241
How black holes get their kicks: Radiation recoil in binary black hole mergers
Gravitational waves from the coalescence of binary black holes carry linear momentum, causing center of mass recoil. This ``radiation rocket'' has important implications for systems with escape speeds of order the recoil velocity. We describe new recoil calculations using high precision black hole perturbation theory to estimate the magnitude of the recoil for the slow ``inspiral'' coalescence phase; coupled with a cruder calculation for the final ``plunge'', we estimate the total recoil imparted to a merged black hole. We find that velocities of many tens to a few hundred km/sec can be achieved fairly easily. The recoil probably never exceeds about 500 km/sec.
4322218
A Cepheid distance to the Fornax cluster and the local expansion rate of the Universe
Both galaxy distances and velocities are required for the determination of the expansion rate of the Universe, as described by the Hubble constant H0. The radial velocities of galaxies arise not just from this expansion but also from random components and large-scale flows. To reach out to distances dominated by the overall cosmic expansion, it is necessary to probe large physical scales where galaxy–galaxy and galaxy–cluster interactions become lessimportant. But accurate distances of nearby galaxies and clusters (commonly measured using Cepheid variable stars) are nevertheless required to calibrate the indirect distance indicators generally used to measure these large scales. Here we report aCepheid distance of 18.6 ± 1.9 (statistical error) ± 1.9 Mpc (systematic error) for the galaxy NGC1365 in Fornax, a cluster of galaxies in the Southern Hemisphere. We find a value of H0 = 70 km s−1 Mpc−1 from Fornax alone, and 73 km s−1 Mpc−1 from the intervening galaxy flow, each corrected for infall into the Virgo cluster. These values are consistent with the Hubble constant measured in the far field using secondary methods. Our data support previous suggestions that the local small-scale velocity field has very small scatter (∼±70 km s−1).
9491059
Localizing Coalescing Massive Black Hole Binaries with Gravitational Waves
Massive black hole binary coalescences are prime targets for space-based gravitational wave (GW) observatories such as LISA. GW measurements can localize the position of a coalescing binary on the sky to an ellipse with a major axis of a few tens of arcminutes to a few degrees, depending on source redshift, and a minor axis which is 2-4 times smaller. Neglecting weak gravitational lensing, the GWs would also determine the source's luminosity distance to better than percent accuracy for close sources, degrading to several percent for more distant sources. Weak lensing cannot, in fact, be neglected and is expected to limit the accuracy with which distances can be fixed to errors no less than a few percent. Assuming a well-measured cosmology, the source's redshift could be inferred with similar accuracy. GWs alone can thus pinpoint a binary to a three-dimensional "pixel" which can help guide searches for the hosts of these events. We examine the time evolution of this pixel, studying it at merger and at several intervals before merger. One day before merger, the major axis of the error ellipse is typically larger than its final value by a factor of ~1.5-6. The minor axis is larger by a factor of ~2-9, and, neglecting lensing, the error in the luminosity distance is larger by a factor of ~1.5-7. This large change over a short period of time is due to spin-induced precession, which is strongest in the final days before merger. The evolution is slower as we go back further in time. For z = 1, we find that GWs will localize a coalescing binary to within ~10 deg2 as early as a month prior to merger and determine distance (and hence redshift) to several percent.
18086963
Implementing fully relativistic hydrodynamics in three dimensions
We report on our numerical implementation of fully relativistic hydrodynamics coupled to Einstein’s field equations in three spatial dimensions. We briefly review several steps in our code development, including our recasting of Einstein’s equations and several tests which demonstrate its advantages for numerical integrations. We outline our implementation of relativistic hydrodynamics, and present numerical results for the evolution of both stable and unstable Oppenheimer-Volkov equilibrium stars, which represent a very promising first test of our code.
119250260
Gravitational Waves from Merging Compact Binaries
Largely motivated by the development of highly sensitive gravitational-wave detectors, our understanding of merging compact binaries and the gravitational waves they generate has improved dramatically in recent years. Breakthroughs in numerical relativity now allow us to model the coalescence of two black holes with no approximations or simplifications. There has also been outstanding progress in our analytical understanding of binaries. We review these developments, examining merging binaries using black hole perturbation theory, post-Newtonian expansions, and direct numerical integration of the field equations. We summarize these approaches and what they have taught us about gravitational waves from compact binaries. We place these results in the context of gravitational-wave generating systems, analyzing the impact gravitational-wave emission has on their sources, as well as what we can learn about them from direct gravitational-wave measurements.