3,790 research outputs found
Early Science with the Karoo Array Telescope: a Mini-Halo Candidate in Galaxy Cluster Abell 3667
Abell 3667 is among the most well-studied galaxy clusters in the Southern
Hemisphere. It is known to host two giant radio relics and a head-tail radio
galaxy as the brightest cluster galaxy. Recent work has suggested the
additional presence of a bridge of diffuse synchrotron emission connecting the
North-Western radio relic with the cluster centre. In this work, we present
full-polarization observations of Abell 3667 conducted with the Karoo Array
Telescope at 1.33 and 1.82 GHz. Our results show both radio relics as well as
the brightest cluster galaxy. We use ancillary higher-resolution data to
subtract the emission from this galaxy, revealing a localised excess, which we
tentatively identify as a radio mini-halo. This mini-halo candidate has an
integrated flux density of mJy beam at 1.37 GHz,
corresponding to a radio power of P
W Hz, consistent with established trends in mini-halo power scaling.Comment: 17 pages, 10 figures, accepted MNRA
Topological interface engineering and defect crossing in ultracold atomic gases
We propose an experimentally feasible scheme for topological interface
engineering and show how it can be used for studies of dynamics of
topologically nontrivial interfaces and perforation of defects and textures
across such interfaces. The method makes use of the internal spin structure of
the atoms together with locally applied control of interaction strengths to
create many-particle states with highly complex topological properties. In
particular, we consider a constructed coherent interface between topologically
distinct phases of spinor Bose-Einstein condensates.Comment: 9 pages, 7 figure
Properties of finite Gaussians and the discrete-continuous transition
Weyl's formulation of quantum mechanics opened the possibility of studying
the dynamics of quantum systems both in infinite-dimensional and
finite-dimensional systems. Based on Weyl's approach, generalized by Schwinger,
a self-consistent theoretical framework describing physical systems
characterised by a finite-dimensional space of states has been created. The
used mathematical formalism is further developed by adding finite-dimensional
versions of some notions and results from the continuous case. Discrete
versions of the continuous Gaussian functions have been defined by using the
Jacobi theta functions. We continue the investigation of the properties of
these finite Gaussians by following the analogy with the continuous case. We
study the uncertainty relation of finite Gaussian states, the form of the
associated Wigner quasi-distribution and the evolution under free-particle and
quantum harmonic oscillator Hamiltonians. In all cases, a particular emphasis
is put on the recovery of the known continuous-limit results when the dimension
of the system increases.Comment: 21 pages, 4 figure
Supersymmetric Jaynes-Cummings model and its exact solutions
The super-algebraic structure of a generalized version of the Jaynes-Cummings
model is investigated. We find that a Z2 graded extension of the so(2,1) Lie
algebra is the underlying symmetry of this model. It is isomorphic to the
four-dimensional super-algebra u(1/1) with two odd and two even elements.
Differential matrix operators are taken as realization of the elements of the
superalgebra to which the model Hamiltonian belongs. Several examples with
various choices of superpotentials are presented. The energy spectrum and
corresponding wavefunctions are obtained analytically.Comment: 12 pages, no figure
Preliminary Measurements of the Motion of Arcjet Current Channel Using Inductive Magnetic Probes
This paper covers the design and first measurements of non-perturbative, external inductive magnetic diagnostics for arcjet constrictors which can measure the motion of the arc current channel. These measurements of arc motion are motivated by previous simulations using the ARC Heater Simulator (ARCHeS), which predicted unsteady arc motion due to the magnetic kink instability. Measurements of the kink instability are relevant to characterizing motion of the enthalpy profile of the arcjet, the arcjet operational stability, and electrode damage due to associated arc detachment events. These first measurements indicate 4 mm oscillations at 0.5-2 kHz of the current profile
Radiative Phase Transitions and Casmir Effect Instabilities
Molecular quantum electrodynamics leads to photon frequency shifts and thus
to changes in condensed matter free energies often called the Casimir effect.
Strong quantum electrodynamic coupling between radiation and molecular motions
can lead to an instability beyond which one or more photon oscillators undergo
a displacement phase transition. The phase boundary of the transition can be
located by a Casimir free energy instability.Comment: ReVTeX4 format 1 *.eps figur
Partial Wave Analysis of Scattering with Nonlocal Aharonov-Bohm Effect and Anomalous Cross Section induced by Quantum Interference
Partial wave theory of a three dmensional scattering problem for an arbitray
short range potential and a nonlocal Aharonov-Bohm magnetic flux is
established. The scattering process of a ``hard shere'' like potential and the
magnetic flux is examined. An anomalous total cross section is revealed at the
specific quantized magnetic flux at low energy which helps explain the
composite fermion and boson model in the fractional quantum Hall effect. Since
the nonlocal quantum interference of magnetic flux on the charged particles is
universal, the nonlocal effect is expected to appear in quite general potential
system and will be useful in understanding some other phenomena in mesoscopic
phyiscs.Comment: 6 figure
The exponential law: Monopole detectors, Bogoliubov transformations, and the thermal nature of the Euclidean vacuum in RP^3 de Sitter spacetime
We consider scalar field theory on the RP^3 de Sitter spacetime (RP3dS),
which is locally isometric to de Sitter space (dS) but has spatial topology
RP^3. We compare the Euclidean vacua on RP3dS and dS in terms of three
quantities that are relevant for an inertial observer: (i) the stress-energy
tensor; (ii) the response of an inertial monopole particle detector; (iii) the
expansion of the Euclidean vacuum in terms of many-particle states associated
with static coordinates centered at an inertial world line. In all these
quantities, the differences between RP3dS and dS turn out to fall off
exponentially at early and late proper times along the inertial trajectory. In
particular, (ii) and (iii) yield at early and late proper times in RP3dS the
usual thermal result in the de Sitter Hawking temperature. This conforms to
what one might call an exponential law: in expanding locally de Sitter
spacetimes, differences due to global topology should fall off exponentially in
the proper time.Comment: 22 pages, REVTex v3.1 with amsfonts and epsf, includes 2 eps figures.
(v2: Minor typos corrected, references updated.
Classical and quantum radiation from a moving charge in an expanding universe
We investigate photon emission from a moving particle in an expanding
universe. This process is analogous to the radiation from an accelerated charge
in the classical electromagnetic theory. Using the framework of quantum field
theory in curved spacetime, we demonstrate that the Wentzel-Kramers-Brillouin
(WKB) approximation leads to the Larmor formula for the rate of the radiation
energy from a moving charge in an expanding universe. Using exactly solvable
models in a radiation-dominated universe and in a Milne universe, we examine
the validity of the WKB formula. It is shown that the quantum effect suppresses
the radiation energy in comparison with the WKB formula.Comment: 16 pages, JCAP in pres
More on coupling coefficients for the most degenerate representations of SO(n)
We present explicit closed-form expressions for the general group-theoretical
factor appearing in the alpha-topology of a high-temperature expansion of
SO(n)-symmetric lattice models. This object, which is closely related to
6j-symbols for the most degenerate representation of SO(n), is discussed in
detail.Comment: 9 pages including 1 table, uses IOP macros Update of Introduction and
Discussion, References adde
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