10,941 research outputs found
Gravitational Chern-Simons and the adiabatic limit
We compute the gravitational Chern-Simons term explicitly for an adiabatic
family of metrics using standard methods in general relativity. We use the fact
that our base three-manifold is a quasi-regular K-contact manifold heavily in
this computation. Our key observation is that this geometric assumption
corresponds exactly to a Kaluza-Klein Ansatz for the metric tensor on our three
manifold, which allows us to translate our problem into the language of general
relativity. Similar computations have been performed in a paper of Guralnik,
Iorio, Jackiw and Pi (2003), although not in the adiabatic context.Comment: 17 page
Anisotropic valence-->core x-ray fluorescence from a [Rh(en)3][Mn(N)(CN)5]·H2O single crystal: Experimental results and density functional calculations
High resolution x-ray fluorescence spectra have been recorded for emission in different directions from a single crystal of the compound [Rh(en)3][Mn(N)(CN)5]·H2O. The spectra are interpreted by comparison with density functional theory (DFT) electronic structure calculations. The Kbeta[double-prime] line, which is strongly polarized along the MnâN axis, can be viewed as an N(2s)-->Mn(1s) transition, and the angular dependence is understood within the dipole approximation. The so-called Kbeta2,5 region has numerous contributions but is dominated by Mn(4p) and C(2s)-->Mn(1s) transitions. Transition energy splittings are found in agreement with those of calculated occupied molecular orbitals to within 1 eV. Computed relative transition probabilities reproduce experimentally observed trends
The issue of time in generally covariant theories and the Komar-Bergmann approach to observables in general relativity
Diffeomorphism-induced symmetry transformations and time evolution are
distinct operations in generally covariant theories formulated in phase space.
Time is not frozen. Diffeomorphism invariants are consequently not necessarily
constants of the motion. Time-dependent invariants arise through the choice of
an intrinsic time, or equivalently through the imposition of time-dependent
gauge fixation conditions. One example of such a time-dependent gauge fixing is
the Komar-Bergmann use of Weyl curvature scalars in general relativity. An
analogous gauge fixing is also imposed for the relativistic free particle and
the resulting complete set time-dependent invariants for this exactly solvable
model are displayed. In contrast with the free particle case, we show that
gauge invariants that are simultaneously constants of motion cannot exist in
general relativity. They vary with intrinsic time
Lagrangian approach to a symplectic formalism for singular systems
We develop a Lagrangian approach for constructing a symplectic structure for
singular systems. It gives a simple and unified framework for understanding the
origin of the pathologies that appear in the Dirac-Bergmann formalism, and
offers a more general approach for a symplectic formalism, even when there is
no Hamiltonian in a canonical sense. We can thus overcome the usual limitations
of the canonical quantization, and perform an algebraically consistent
quantization for a more general set of Lagrangian systems.Comment: 30 page
A Compact Approximate Solution to the Friedel-Anderson Impuriy Problem
An approximate groundstate of the Anderson-Friedel impurity problem is
presented in a very compact form. It requires solely the optimization of two
localized electron states and consists of four Slater states (Slater
determinants). The resulting singlet ground state energy lies far below the
Anderson mean field solution and agrees well with the numerical results by
Gunnarsson and Schoenhammer, who used an extensive 1/N_{f}-expansion for a spin
1/2 impurity with double occupancy of the impurity level.
PACS: 85.20.Hr, 72.15.R
Hardware support for real-time reconfigurable system-on-chip
This paper introduces a computer architecture suitable for embedded real-time applications where low power consumption is a requirement. This is achieved through the use of a hybrid hardware-software system. A system architecture is proposed which allows for modules of a system to be implemented at run-time in either hardware or software. Implementation choices may be made dynamically based on the loading of the host microprocessor, in a multi-tasking environment. An approach to inter-module communication is described, along with how this is affected by dynamic configuration. Some research goals are identified, including investigating the effects on real-time performance, power consumption and the design process involved in reconfigurable systems
Oscillations of the magnetic polarization in a Kondo impurity at finite magnetic fields
The electronic properties of a Kondo impurity are investigated in a magnetic
field using linear response theory. The distribution of electrical charge and
magnetic polarization are calculated in real space. The (small) magnetic field
does not change the charge distribution. However, it unmasks the Kondo cloud.
The (equal) weight of the d-electron components with their magnetic moment up
and down is shifted and the compensating s-electron clouds don't cancel any
longer (a requirement for an experimental detection of the Kondo cloud). In
addition to the net magnetic polarization of the conduction electrons an
oscillating magnetic polarization with a period of half the Fermi wave length
is observed. However, this oscillating magnetic polarization does not show the
long range behavior of Rudermann-Kittel-Kasuya-Yosida oscillations because the
oscillations don't extend beyond the Kondo radius. They represent an internal
electronic structure of the Kondo impurity in a magnetic field. PACS: 75.20.Hr,
71.23.An, 71.27.+
ARIA 2016 : Care pathways implementing emerging technologies for predictive medicine in rhinitis and asthma across the life cycle
European Innovation Partnership on Active and Healthy Ageing Reference Site MACVIA-France, EU Structural and Development Fund Languedoc-Roussillon, ARIA.Peer reviewedPublisher PD
The Ultraviolet Spectra of Active Galaxies With Double-Peaked Emission Lines
We present the results of UV spectroscopy of AGNs with double-peaked Balmer
emission lines. In 2/3 of the objects, the far-UV resonance lines are strong,
with single-peaked profiles resembling those of Seyfert galaxies. The Mg II
line is the only UV line with a double-peaked profile. In the remaining
objects, the far-UV resonance lines are relatively weak but still
single-peaked. The latter group also displays prominent UV absorption lines,
indicative of a low-ionization absorber. We interpret the difference in the
profiles of the emission lines as resulting from two different regions: a
dense, low-ionization accretion disk (the predominant source of the Balmer and
Mg II lines), and a lower density, higher-ionization wind (the predominant
source of the far-UV resonance lines). These results suggest a way of
connecting the double-peaked emitters with the greater AGN population: in
double-peaked emitters the accretion rate onto the black hole is low, making
the wind feeble and allowing the lines from the underlying disk to shine
through. This scenario also implies that in the majority of AGNs, the wind is
the source of the broad emission lines.Comment: To appear in "The Interplay among Black Holes, Stars and ISM in
Galactic Nuclei," IAU Coll. 222, eds. Storchi Bergmann, Ho, and Schmit
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