67,530 research outputs found
Matching Conditions on Capillary Ripples: Polarization
The matching conditions at the interface between two non-mixed fluids at rest
are obtained directly using the equation of movement of the whole media. This
is a non-usual point of view in hydrodynamics courses and our aim is to fix
ideas about the intrinsic information contained in the matching conditions, on
fluids in this case. Afterward, it is analyzed the polarization of the normal
modes at the interface and it is shown that this information can be achieved
through a physical analysis and reinforced later by the matching conditions. A
detailed analysis of the matching conditions is given to understand the role
that plays the continuity of the stress tensor through the interface on the
physics of the surface particle movement. The main importance of the viscosity
of each medium is deduced.Comment: 5 pages, two columns, 1 .ps figure. Submitted to Rev. Mex. Fisic
Heisenberg uniqueness pairs and the Klein-Gordon equation
The notion of a Heisenberg Uniqueness Pair (HUP) is introduced. This amounts
to asking which collections of exponentials are weak-star fundamental in
on a planar curve. In the case when the curve is a hyperbola, we can
give a complete answer if the frequencies are restricted to equally spaced
points on a lattice-cross. As a consequence, we solve a problem on the density
of algebras generated by two inner functions raised by Matheson and Stessin.Comment: 16 page
The ionization equilibrium of iron in H II regions
We study the ionization equilibrium of Fe using photoionization models that
incorporate improved values for the ionization and recombination cross-sections
and the charge-exchange rates for the Fe ions. The previously available
photoionization models predict concentrations of Fe3+ which are a factor of 3-8
higher than the values inferred from emission lines of [Fe III] and [Fe IV].
Our new models reduce these discrepancies to factors of 2-5. We discuss the
possible reasons behind the remaining discrepancies and present an updated
ionization correction factor for obtaining the Fe abundance from the Fe++
abundance.Comment: 4 pages, 1 figure, extended version of the paper to be published in
"Recycling intergalactic and interstellar matter", IAU Symposium Series, Vol.
217, 2004, P.-A. Duc, J. Braine and E. Brinks, ed
The photon magnetic moment has not a perpendicular component and is fully paramagnetic
Our paper Phys. Rev. D \textbf{79}, 093002 (2009), in which it was shown the
paramagnetic behavior of photons propagating in magnetized vacuum, is
criticized in Phys. Rev. D \textbf{81}, 105019, (2010) and even claimed that
the photon has a diamagnetic component. Here it is shown that such criticism is
inadequate and that the alleged "perpendicular component" is due to a mistake
in differentiating a vanishing term with regard to the magnetic field , or
either by mistaking the derivative of a scalar product as that of a dyadic
product. A discussion on the physical side of the problem is also made
Is the photon paramagnetic?
A photon exhibits a tiny anomalous magnetic moment due to its
interaction with an external constant magnetic field in vacuum through the
virtual electron-positron background. It is paramagnetic () in
the whole region of transparency, i.e. below the first threshold energy for
pair creation and has a maximum near this threshold. The photon magnetic moment
is different for eigenmodes polarized along and perpendicular to the magnetic
field. Explicit expressions are given for for the cases of
photon energies smaller and closer to the first pair creation threshold. The
region beyond the first threshold is briefly discussed
Vacuum pressures and energy in a strong magnetic field
We study vacuum in a strong magnetic field. It shows a nonlinear response, as
a ferromagnetic medium. Anisotropic pressures arise, and a negative pressure is
exerted in the direction perpendicular to the field. The analogy of this effect
with the Casimir effect is analyzed. The vacuum transverse pressure is found to
be of the same order of the statistical pressure for and
. Vacuum interaction with the field is studied
also for and larger, including the electron anomalous magnetic
moment. We estimate quark contribution to vacuum behavior.Comment: Presented in the International Workshop on Strong Magnetic Fields and
Neutron Stars, Havana, Cuba, April 200
Series expansion of the photon self-energy in QED and the photon anomalous magnetic moment
We start from the analytical expression of the eigenvalues of
the photon self-energy tensor in an external constant magnetic field
calculated by Batalin Shabad in the Furry representation, and in the one-loop
approximation. We expand in power series of the external field and in terms of
the squared photon transverse momentum and (minus) transverse energy
, in terms of which are expressed . A general
expression is given for the photon anomalous magnetic moment
in the region of transparency, below the first threshold for pair creation, and
it is shown that it is positive, i.e. paramagnetic. The results of the
numerical calculation for are displayed in a region close to
the threshold
Magnetic Fields in Quantum Degenerate Systems and in Vacuum
We consider self-magnetization of charged and neutral vector bosons bearing a
magnetic moment in a gas and in vacuum. For charged vector bosons (W bosons) a
divergence of the magnetization in both the medium and the electroweak vacuum
occurs for the critical field B=B_{wc}=m_{w}^{2}/e. For B>B_{wc} the system is
unstable. This behavior suggests the occurrence of a phase transition at
B=B_{c}, where the field is self-consistently maintained. This mechanism
actually prevents from reaching the critical value B_{c}. For virtual
neutral vector bosons bearing an anomalous magnetic moment, the ground state
has a similar behavior for B=B_{nbc}=m_{nb}^{2}/q . The magnetization in the
medium is associated to a Bose-Einstein condensate and we conjecture a similar
condensate occurs also in the case of vacuum.
The model is applied to virtual electron-positron pairs bosonization in a
magnetic field B \sim B_{pc}\lesssim 2m_{e}^{2}/e, where m_e is the electron
mass. This would lead also to vacuum self-magnetization in QED, where in both
cases the symmetry breaking is due to a condensate of quasi-massless particles
Quantized Faraday effect in (3+1)-dimensional and (2+1)-dimensional systems
We study Faraday rotation in the quantum relativistic limit. Starting from
the photon self-energy in the presence of a constant magnetic field the
rotation of the polarization vector of a plane electromagnetic wave which
travel along the fermion-antifermion gas is studied. The connection between
Faraday Effect and Quantum Hall Effect (QHE) is discussed. The Faraday Effect
is also investigated for a massless relativistic (2D+1)-dimensional fermion
system which is derived by using the compactification along the dimension
parallel to the magnetic field. The Faraday angle shows a quantized behavior as
Hall conductivity in two and three dimensions.Comment: 15 pages, 5 figure
Quantum Walks with Gremlin
A quantum walk places a traverser into a superposition of both graph location
and traversal "spin." The walk is defined by an initial condition, an evolution
determined by a unitary coin/shift-operator, and a measurement based on the
sampling of the probability distribution generated from the quantum
wavefunction. Simple quantum walks are studied analytically, but for large
graph structures with complex topologies, numerical solutions are typically
required. For the quantum theorist, the Gremlin graph traversal machine and
language can be used for the numerical analysis of quantum walks on such
structures. Additionally, for the graph theorist, the adoption of quantum walk
principles can transform what are currently side-effect laden traversals into
pure, stateless functional flows. This is true even when the constraints of
quantum mechanics are not fully respected (e.g. reversible and unitary
evolution). In sum, Gremlin allows both types of theorist to leverage each
other's constructs for the advancement of their respective disciplines.Comment: GraphDay '16, 1(1), pages 1-16, Austin Texas, January 201
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