7,538 research outputs found
Roughness correction to the Casimir force : Beyond the Proximity Force Approximation
We calculate the roughness correction to the Casimir effect in the parallel
plates geometry for metallic plates described by the plasma model. The
calculation is perturbative in the roughness amplitude with arbitrary values
for the plasma wavelength, the plate separation and the roughness correlation
length. The correction is found to be always larger than the result obtained in
the Proximity Force Approximation.Comment: 7 pages, 3 figures, v2 with minor change
Particle Creation by a Moving Boundary with Robin Boundary Condition
We consider a massless scalar field in 1+1 dimensions satisfying a Robin
boundary condition (BC) at a non-relativistic moving boundary. We derive a
Bogoliubov transformation between input and output bosonic field operators,
which allows us to calculate the spectral distribution of created particles.
The cases of Dirichlet and Neumann BC may be obtained from our result as
limiting cases. These two limits yield the same spectrum, which turns out to be
an upper bound for the spectra derived for Robin BC. We show that the particle
emission effect can be considerably reduced (with respect to the
Dirichlet/Neumann case) by selecting a particular value for the oscillation
frequency of the boundary position
Dynamical aspects of Kinouchi-Copelli model: emergence of avalanches at criticality
We analyze the behavior of bursts of neural activity in the Kinouchi-Copelli
model, originally conceived to explain information processing issues in sensory
systems. We show that, at a critical condition, power-law behavior emerges for
the size and duration of the bursts (avalanches), with exponents experimentally
observed in real biological systems.Comment: Paper accepted for Brazilian Conference on Dynamics, Control and
Applications (oral presentation and poster). 4 pages, 5 figure
Dynamical Casimir effect with cylindrical waveguides
I consider the quantum electromagnetic field in a coaxial cylindrical
waveguide, such that the outer cylindrical surface has a time-dependent radius.
The field propagates parallel to the axis, inside the annular region between
the two cylindrical surfaces. When the mechanical frequency and the thickness
of the annular region are small enough, only Transverse Electromagnetic (TEM)
photons may be generated by the dynamical Casimir effect. The photon emission
rate is calculated in this regime, and compared with the case of parallel
plates in the limit of very short distances between the two cylindrical
surfaces. The proximity force approximation holds for the transition matrix
elements in this limit, but the emission rate scales quadratically with the
mechanical frequency, as opposed to the cubic dependence for parallel plates.Comment: 6 page
Axial dependence of optical weak measurements in the critical region
The interference between optical beams of different polarizations plays a
fundamental role in reproducing the optical analog of the electron spin weak
measurement. The extraordinary point in optical weak measurements is
represented by the possibility to estimate with great accuracy the
Goos-Haenchen (GH) shift by measuring the distance between the peak of the
outgoing beams for two opposite rotation angles of the polarizers located
before and after the dielectric block. Starting from the numerical calculation
of the GH shift, which clearly shows a frequency crossover for incidence near
to the critical angle, we present a detailed study of the interference between
s and p polarized waves in the critical region. This allows to determine in
which conditions it is possible to avoid axial deformations and reproduce the
GH curves. In view of a possible experimental implementation, we give the
expected weak measurement curves for Gaussian lasers of different beam waist
sizes propagating through borosilicate (BK7) and fused silica dielectric
blocks.Comment: 16 pages, 7 figure
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