15,210 research outputs found
Submillimeter H2O masers in water-fountain nebulae
We report the first detection of submillimeter water maser emission toward
water-fountain nebulae, which are post-AGB stars that exhibit high-velocity
water masers. Using APEX we found emission in the ortho-H2O (10_29-9_36)
transition at 321.226 GHz toward three sources: IRAS 15445-5449, IRAS
18043-2116 and IRAS 18286-0959. Similarly to the 22 GHz masers, the
submillimeter water masers are expanding with a velocity larger than that of
the OH masers, suggesting that these masers also originate in fast bipolar
outflows. In IRAS 18043-2116 and IRAS 18286-0959, which figure among the
sources with the fastest water masers, the velocity range of the 321 GHz masers
coincides with that of the 22 GHz masers, indicating that they likely coexist.
Towards IRAS 15445-5449 the submillimeter masers appear in a different velocity
range, indicating that they are tracing different regions. The intensity of the
submillimeter masers is comparable to that of the 22 GHz masers, implying that
the kinetic temperature of the region where the masers originate should be Tk >
1000 K. We propose that the passage of two shocks through the same gas can
create the conditions necessary to explain the presence of strong high-velocity
321 GHz masers coexisting with the 22 GHz masers in the same region.Comment: 4 pages, 1 figure. Accepted for publication in A&A Letter
Entanglement of a qubit coupled to a resonator in the adiabatic regime
We discuss the ground state entanglement of a bi-partite system, composed by
a qubit strongly interacting with an oscillator mode, as a function of the
coupling strenght, the transition frequency and the level asymmetry of the
qubit. This is done in the adiabatic regime in which the time evolution of the
qubit is much faster than the oscillator one. Within the adiabatic
approximation, we obtain a complete characterization of the ground state
properties of the system and of its entanglement content.Comment: 6 pages, 7 figure
Dynamics of Entanglement and Bell-nonlocality for Two Stochastic Qubits with Dipole-Dipole Interaction
We have studied the analytical dynamics of Bell nonlocality as measured by
CHSH inequality and entanglement as measured by concurrence for two noisy
qubits that have dipole-dipole interaction. The nonlocal entanglement created
by the dipole-dipole interaction is found to be protected from sudden death for
certain initial states
Sudden vanishing and reappearance of nonclassical effects: General occurrence of finite-time decays and periodic vanishings of nonclassicality and entanglement witnesses
Analyses of phenomena exhibiting finite-time decay of quantum entanglement
have recently attracted considerable attention. Such decay is often referred to
as sudden vanishing (or sudden death) of entanglement, which can be followed by
its sudden reappearance (or sudden rebirth). We analyze various finite-time
decays (for dissipative systems) and analogous periodic vanishings (for unitary
systems) of nonclassical correlations as described by violations of classical
inequalities and the corresponding nonclassicality witnesses (or quantumness
witnesses), which are not necessarily entanglement witnesses. We show that
these sudden vanishings are universal phenomena and can be observed: (i) not
only for two- or multi-mode but also for single-mode nonclassical fields, (ii)
not solely for dissipative systems, and (iii) at evolution times which are
usually different from those of sudden vanishings and reappearances of quantum
entanglement.Comment: 10 pages, 3 figure
A New Derivation of the CPT and Spin-Statistics Theorems in Non-Commutative Field Theories
We propose an alternative axiomatic description for non-commutative field
theories (NCFT) based on some ideas by Soloviev to nonlocal quantum fields. The
local commutativity axiom is replaced by the weaker condition that the fields
commute at sufficiently large spatial separations, called asymptotic
commutativity, formulated in terms of the theory of analytic functionals. The
question of a possible violation of the CPT and Spin-Statistics theorems caused
by nonlocality of the commutation relations
is investigated. In spite of this
inherent nonlocality, we show that the modification aforementioned is
sufficient to ensure the validity of these theorems for NCFT. We restrict
ourselves to the simplest model of a scalar field in the case of only
space-space non-commutativity.Comment: The title is new, and the analysis in the manuscript has been made
more precise. This revised version is to be published in J.Math.Phy
Maximal Commutative Subalgebras Invariant for CP-Maps: (Counter-)Examples
We solve, mainly by counterexamples, many natural questions regarding maximal
commutative subalgebras invariant under CP-maps or semigroups of CP-maps on a
von Neumann algebra. In particular, we discuss the structure of the generators
of norm continuous semigroups on B(G) leaving a maximal commutative subalgebra
invariant and show that there exists Markov CP-semigroups on M_d without
invariant maximal commutative subalgebras for any d>2.Comment: After the elemenitation in Version 2 of a false class of examples in
Version 1, we now provide also correct examples for unital CP-maps and Markov
semigroups on M_d for d>2 without invariant masa
Quivers, Tilings, Branes and Rhombi
We describe a simple algorithm that computes the recently discovered brane
tilings for a given generic toric singular Calabi-Yau threefold. This therefore
gives AdS/CFT dual quiver gauge theories for D3-branes probing the given
non-compact manifold. The algorithm solves a longstanding problem by computing
superpotentials for these theories directly from the toric diagram of the
singularity. We study the parameter space of a-maximization; this study is made
possible by identifying the R-charges of bifundamental fields as angles in the
brane tiling. We also study Seiberg duality from a new perspective.Comment: 36 pages, 40 figures, JHEP
Comments on the non-conformal gauge theories dual to Ypq manifolds
We study the infrared behavior of the entire class of Y(p,q) quiver gauge
theories. The dimer technology is exploited to discuss the duality cascades and
support the general belief about a runaway behavior for the whole family. We
argue that a baryonic classically flat direction is pushed to infinity by the
appearance of ADS-like terms in the effective superpotential. We also study in
some examples the IR regime for the L(a,b,c) class showing that the same
situation might be reproduced in this more general case as well.Comment: 48 pages, 27 figures; updated reference
Meta-Stable Brane Configuration with Orientifold 6 Plane
We present the intersecting brane configuration of type IIA string theory
corresponding to the meta-stable nonsupersymmetric vacua in four dimensional
N=1 supersymmetric SU(N_c) gauge theory with a symmetric flavor, a conjugate
symmetric flavor and fundamental flavors. By studying the previously known
supersymmetric M5-brane curve, the M-theory lift for this type IIA brane
configuration, which consists of NS5-branes, D4-branes, D6-branes and an
orientifold 6-plane, is analyzed.Comment: 21 pp, 3 colored figures; stability arguments added in page 11 and
12, a typo in figure 3 corrected, and to appear in JHE
Uso da espectroscopia e tomografia de ressonância magnética para monitorar o amadurecimento e fatores de qualidade em manga e mamão.
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