27,928 research outputs found
Interplay of disorder and geometrical frustration in doped Gadolinium Gallium Garnet
The geometrically-frustrated, triangular antiferromagnet GGG exhibits a rich
mix of short-range order and isolated quantum states. We investigate the
effects of up to 1% Neodymium substitution for Gallium on the ac magnetic
response at temperatures below 1 K in both the linear and nonlinear regimes.
Substitutional disorder actually drives the system towards a more perfectly
frustrated state, apparently compensating for the effect of imperfect
Gadolinium/Gallium stoichiometry, while at the same time more closely
demarcating the boundaries of isolated, coherent clusters composed of hundreds
of spins. Optical measurements of the local Nd environment substantiate the
picture of an increased frustration index with doping.Comment: 5 pages, 5 figure
Instability of Quark Matter Core in a Compact Newborn Neutron Star With Moderately Strong Magnetic Field
It is explicitly shown that if phase transition occurs at the core of a
newborn neutron star with moderately strong magnetic field strength, which
populates only the electron's Landau levels, then in the -equilibrium
condition, the quark core is energetically much more unstable than the neutron
matter of identical physical condition.Comment: Six pages REVTEX file, one .eps file (included
Bragg spectroscopy of a cigar shaped Bose condensate in optical lattices
We study properties of excited states of an array of weakly coupled
quasi-two-dimensional Bose condensates by using the hydrodynamic theory. We
calculate multibranch Bogoliubov-Bloch spectrums and its corresponding
eigenfunctions. The spectrum of the axial excited states and its eigenfunctions
strongly depends on the coupling among various discrete radial modes within a
given symmetry. This mode coupling is due to the presence of radial trapping
potential. The multibranch nature of the Bogoliubov-Bloch spectrum and its
dependence on the mode-coupling can be realized by analyzing dynamic structure
factor and momentum transferred to the system in Bragg spectroscopy
experiments. We also study dynamic structure factor and momentum transferred to
the condensate due to the Bragg spectroscopy experiment.Comment: 7 pages, 5 figures, to appear in Journal of Physics B: Atomic,
Molecular & Optical Physic
Chiral Properties of QCD Vacuum in Magnetars- A Nambu-Jona-Lasinio Model with Semi-Classical Approximation
The breaking of chiral symmetry of light quarks at zero temperature in
presence of strong quantizing magnetic fiels is studied using
Nambu-Jona-Lasinio (NJL) model with Thomas-Fermi type semi-classical formalism.
It is found that the dynamically generated light quark mass can never become
zero if the Landau levels are populated and the mass increases with the
increase of magnetic field strength.Comment: REVTEX 11 Pages, One .eps figure (included
Neuromorphic In-Memory Computing Framework using Memtransistor Cross-bar based Support Vector Machines
This paper presents a novel framework for designing support vector machines
(SVMs), which does not impose restriction on the SVM kernel to be
positive-definite and allows the user to define memory constraint in terms of
fixed template vectors. This makes the framework scalable and enables its
implementation for low-power, high-density and memory constrained embedded
application. An efficient hardware implementation of the same is also
discussed, which utilizes novel low power memtransistor based cross-bar
architecture, and is robust to device mismatch and randomness. We used
memtransistor measurement data, and showed that the designed SVMs can achieve
classification accuracy comparable to traditional SVMs on both synthetic and
real-world benchmark datasets. This framework would be beneficial for design of
SVM based wake-up systems for internet of things (IoTs) and edge devices where
memtransistors can be used to optimize system's energy-efficiency and perform
in-memory matrix-vector multiplication (MVM).Comment: 4 pages, 5 figures, MWSCAS 201
Realization of Optimal Disentanglement by Teleportation via Separable Channel
We discuss here the best disentanglement processes of states of two two-level
systems which belong to (i) the universal set, (ii) the set in which the states
of one party lie on a single great circle of the Bloch sphere, and (iii) the
set in which the states of one party commute with each other, by teleporting
the states of one party (on which the disentangling machine is acting) through
three particular type of separable channels, each of which is a mixture of Bell
states. In the general scenario, by teleporting one party's state of an
arbitrary entangled state of two two-level parties through some mixture of Bell
states, we have shown that this entangled state can be made separable by using
a physically realizable map , acting on one party's states, if
, where
(for ), and .Comment: 20 pages Late
Gravitating magnetic monopole in Vaidya geometry
A magnetic-monopole solution of a non-Abelian gauge theory as proposed by 't
Hooft and Polyakov is studied in the Vaidya spacetime. We find that the
solutions of Einstein equations generates a geometry of the Bonnor-Vaidya
corresponding to magnetically charged null fluid with Higgs field contributing
a cosmological term. In the absence of the scalar fields the corresponding
Wu-Yang solution of the gauge theory still generates the Bonnor-Vaidya
geometry, but with no cosmological term.Comment: 5 RevTeX pages, no figures, minor changes, to appear in Physical
Review
The Arecibo Arp 220 Spectral Census I: Discovery of the Pre-Biotic Molecule Methanimine and New Cm-wavelength Transitions of Other Molecules
An on-going Arecibo line search between 1.1 and 10 GHz of the prototypical
starburst/megamaser galaxy, Arp 220, has revealed a spectrum rich in molecular
transitions. These include the ``pre-biotic'' molecules: methanimine
(CHNH) in emission, three direct l-type absorption lines of
HCN, and an absorption feature likely to be from either OH or formic
acid (HCOOH). In addition, we report the detection of two, possibly three,
transitions of 4-cm excited OH not previously detected in Arp~220
which are seen in absorption, and a possible absorption feature from the
6.668-GHz line of methanol. This marks the first distant extragalactic
detection of methanimine, a pre-biotic molecule. Also, if confirmed, the
possible methanol absorption line presented here would represent the first
extragalactic detection of methanol at a distance further than 10 Mpc. In
addition, the strong, previously undetected, cm-wave HCN direct
l-type lines will aid the study of dense molecular gas and active star-forming
regions in this starburst galaxy.Comment: 25 pages, 10 figures. Accepted for publication in A
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