12,124 research outputs found
The construction of Frobenius manifolds from KP tau-functions
Frobenius manifolds (solutions of WDVV equations) in canonical coordinates
are determined by the system of Darboux-Egoroff equations. This system of
partial differential equations appears as a specific subset of the
-component KP hierarchy. KP representation theory and the related Sato
infinite Grassmannian are used to construct solutions of this Darboux-Egoroff
system and the related Frobenius manifolds. Finally we show that for these
solutions Dubrovin's isomonodromy tau-function can be expressed in the KP
tau-function.Comment: 29 pages, latex2e, no figure
Neutrino and antineutrino quasielastic interactions with nuclei
We investigate the interaction of neutrinos and antineutrinos with nuclei. We
explore in particular the role played by the multinucleon excitations which can
contaminate the quasielastic cross section. For neutrinos the multinucleon term
produces a sizable increase of the quasielastic cross section. Part of the
effect arises from tensor correlations. For antineutrinos this influence is
smaller owing to the axial-vector interference which increases the relative
importance of the terms which are not affected by these multinucleon
excitations
Multiparticle Quantum Superposition and Stimulated Entanglement by Parity Selective Amplification of Entangled States
A multiparticle quantum superposition state has been generated by a novel
phase-selective parametric amplifier of an entangled two-photon state. This
realization is expected to open a new field of investigations on the
persistence of the validity of the standard quantum theory for systems of
increasing complexity, in a quasi decoherence-free environment. Because of its
nonlocal structure the new system is expected to play a relevant role in the
modern endeavor on quantum information and in the basic physics of
entanglement.Comment: 13 pages and 3 figure
Iron Emission in the z=6.4 Quasar SDSS J114816.64+525150.3
We present near-infrared J and K-band spectra of the z = 6.4 quasar SDSS
J114816.64+525150.3 obtained with the NIRSPEC spectrograph at the Keck-II
telescope, covering the rest-frame spectral regions surrounding the C IV 1549
and Mg II 2800 emission lines. The iron emission blend at rest wavelength
2900-3000 A is clearly detected and its strength appears nearly
indistinguishable from that of typical quasars at lower redshifts. The Fe II /
Mg II ratio is also similar to values found for lower-redshift quasars,
demonstrating that there is no strong evolution in Fe/alpha broad-line emission
ratios even out to z=6.4. In the context of current models for iron enrichment
from Type Ia supernovae, this implies that the SN Ia progenitor stars formed at
z > 10. We apply the scaling relations of Vestergaard and of McLure & Jarvis to
estimate the black hole mass from the widths of the C IV and Mg II emission
lines and the ultraviolet continuum luminosity. The derived mass is in the
range (2-6)x10^9 solar masses, with an additional uncertainty of a factor of 3
due to the intrinsic scatter in the scaling relations. This result is in
agreement with the previous mass estimate of 3x10^9 solar masses by Willott,
McLure, & Jarvis, and supports their conclusion that the quasar is radiating
close to its Eddington luminosity.Comment: To appear in ApJ Letter
Separating the classical and quantum information via quantum cloning
An application of quantum cloning to optimally interface a quantum system
with a classical observer is presented, in particular we describe a procedure
to perform a minimal disturbance measurement on a single qubit by adopting a
1->2 cloning machine followed by a generalized measurement on a single clone
and the anti-clone or on the two clones. Such scheme has been applied to
enhance the transmission fidelity over a lossy quantum channel.Comment: 4 pages, 2figure
Active Galactic Nuclei in Groups and Clusters of Galaxies: Detection and Host Morphology
The incidence and properties of Active Galactic Nuclei (AGN) in the field,
groups, and clusters can provide new information about how these objects are
triggered and fueled, similar to how these environments have been employed to
study galaxy evolution. We have obtained new XMM-Newton observations of seven
X-ray selected groups and poor clusters with 0.02 < z < 0.06 for comparison
with previous samples that mostly included rich clusters and optically-selected
groups. Our final sample has ten groups and six clusters in this low-redshift
range (split at a velocity dispersion of km/s). We find that the
X-ray selected AGN fraction increases from in clusters to for the
groups (85% significance), or a factor of two, for AGN above an 0.3-8keV X-ray
luminosity of erg/s hosted by galaxies more luminous than .
The trend is similar, although less significant, for a lower-luminosity host
threshold of mag. For many of the groups in the sample we have also
identified AGN via standard emission-line diagnostics and find that these AGN
are nearly disjoint from the X-ray selected AGN. Because there are substantial
differences in the morphological mix of galaxies between groups and clusters,
we have also measured the AGN fraction for early-type galaxies alone to
determine if the differences are directly due to environment, or indirectly due
to the change in the morphological mix. We find that the AGN fraction in
early-type galaxies is also lower in clusters compared to
for the groups (92% significance), a result consistent with the hypothesis that
the change in AGN fraction is directly connected to environment.Comment: 18 pages, 9 figures; accepted by The Astrophysical Journal; for
higher-resolution versions of some figures, see
http://u.arizona.edu/~tjarnold/Arnold09
Quasielastic electron- and neutrino-nucleus scattering in a continuum random phase approximation approach
We present a continuum random phase approximation approach to study electron-
and neutrino-nucleus scattering cross sections, in the kinematic region where
quasielastic scattering is the dominant process. We show the validity of the
formalism by confronting inclusive () cross sections with the available
data. We calculate flux-folded cross sections for charged-current quasielastic
antineutrino scattering off C and compare them with the MiniBooNE
cross-section measurements. We pay special emphasis to the contribution of
low-energy nuclear excitations in the signal of accelerator-based
neutrino-oscillation experiments.Comment: 5 pages, 5 figures. Contribution to the proceedings of the 16th
International Workshop on Neutrino Factories and Future Neutrino Beam
Facilities (NUFACT-2014
Generation of time-bin entangled photons without temporal post-selection
We report on the implementation of a new interferometric scheme that allows
the generation of photon pairs entangled in the time-energy degree of freedom.
This scheme does not require any kind of temporal post-selection on the
generated pairs and can be used even with lasers with short coherence time.Comment: RevTex, 6 pages, 8 figure
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