12,620 research outputs found
Is it possible to accommodate massive photons in the framework of a gauge-invariant electrodynamics?
The construction of an alternative electromagnetic theory that preserves
Lorentz and gauge symmetries, is considered. We start off by building up
Maxwell electrodynamics in (3+1)D from the assumption that the associated
Lagrangian is a gauge-invariant functional that depends on the electron and
photon fields and their first derivatives only. In this scenario, as
well-known, it is not possible to set up a Lorentz invariant gauge theory
containing a massive photon. We show nevertheless that there exist two
radically different electrodynamics, namely, the Chern-Simons and the Podolsky
formulations, in which this problem can be overcome. The former is only valid
in odd space-time dimensions, while the latter requires the presence of
higher-order derivatives of the gauge field in the Lagrangian. This theory,
usually known as Podolsky electrodynamics, is simultaneously gauge and Lorentz
invariant; in addition, it contains a massive photon. Therefore, a massive
photon, unlike the popular belief, can be adequately accommodated within the
context of a gauge-invariant electrodynamics.Comment: 10 page
Topological insulator particles as optically induced oscillators: towards dynamical force measurements and optical rheology
We report the first experimental study upon the optical trapping and
manipulation of topological insulator (TI) particles. By virtue of the unique
TI properties, which have a conducting surface and an insulating bulk, the
particles present a peculiar behaviour in the presence of a single laser beam
optical tweezers: they oscillate in a plane perpendicular to the direction of
the laser propagation, as a result of the competition between radiation
pressure and gradient forces. In other words, TI particles behave as optically
induced oscillators, allowing dynamical measurements with unprecedented
simplicity and purely optical control. Actually, optical rheology of soft
matter interfaces and biological membranes, as well as dynamical force
measurements in macromolecules and biopolymers, may be quoted as feasible
possibilities for the near future.Comment: 6 pages, 5 figures. Correspondence and requests for Supplementary
Material should be addressed to [email protected]
Rank-(n – 1) convexity and quasiconvexity for divergence free fields
No description supplie
Magnetic control of particle-injection in plasma based accelerators
The use of an external transverse magnetic field to trigger and to control
electron self-injection in laser- and particle-beam driven wakefield
accelerators is examined analytically and through full-scale particle-in-cell
simulations. A magnetic field can relax the injection threshold and can be used
to control main output beam features such as charge, energy, and transverse
dynamics in the ion channel associated with the plasma blowout. It is shown
that this mechanism could be studied using state-of-the-art magnetic fields in
next generation plasma accelerator experiments.Comment: 10 pages, 3 figure
Three-Body Halos in Two Dimensions
A method to study weakly bound three-body quantum systems in two dimensions
is formulated in coordinate space for short-range potentials. Occurrences of
spatially extended structures (halos) are investigated. Borromean systems are
shown to exist in two dimensions for a certain class of potentials. An
extensive numerical investigation shows that a weakly bound two-body state
gives rise to two weakly bound three-body states, a reminiscence of the Efimov
effect in three dimensions. The properties of these two states in the weak
binding limit turn out to be universal.
PACS number(s): 03.65.Ge, 21.45.+v, 31.15.Ja, 02.60NmComment: 9 pages, 2 postscript figures, LaTeX, epsf.st
Demonstration of the Complementarity of One- and Two-Photon Interference
The visibilities of second-order (single-photon) and fourth-order
(two-photon) interference have been observed in a Young's double-slit
experiment using light generated by spontaneous parametric down-conversion and
a photon-counting intensified CCD camera. Coherence and entanglement underlie
one-and two-photon interference, respectively. As the effective source size is
increased, coherence is diminished while entanglement is enhanced, so that the
visibility of single-photon interference decreases while that of two-photon
interference increases. This is the first experimental demonstration of the
complementarity between single- and two-photon interference (coherence and
entanglement) in the spatial domain.Comment: 21 pages, 7 figure
On the magnetic perturbation of the Ising model on the sphere
In this letter we will extend the analysis given by Al. Zamolodchikov for the
scaling Yang-Lee model on the sphere to the Ising model in a magnetic field. A
numerical study of the partition function and of the vacuum expectation values
(VEV) is done by using the truncated conformal space (TCS) approach. Our
results strongly suggest that the partition function is an entire function of
the coupling constant.Comment: 8 pages, 1 figure, revised version, references adde
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