1,064 research outputs found
Magnetic and electric properties of quantum vacuum
In this report we show that vacuum is a nonlinear optical medium and we
discuss what are the optical phenomena that should exist in the framework of
the standard model of particle physics. We pay special attention to the low
energy limit. The predicted effects for photons of energy smaller than the
electron rest mass are of such a level that none has been observed
experimentally yet. Progresses in field sources and related techniques seem to
indicate that in few years vacuum nonlinear optics will be accessible to human
investigation.Comment: Reports on Progress in Physics (2013) in pres
One-dimensional disordered Ising models by replica and cavity methods
Using a formalism based on the spectral decomposition of the replicated
transfer matrix for disordered Ising models, we obtain several results that
apply both to isolated one-dimensional systems and to locally tree-like graph
and factor graph (p-spin) ensembles. We present exact analytical expressions,
which can be efficiently approximated numerically, for many types of
correlation functions and for the average free energies of open and closed
finite chains. All the results achieved, with the exception of those involving
closed chains, are then rigorously derived without replicas, using a
probabilistic approach with the same flavour of cavity method
Four-level N-scheme crossover resonances in Rb saturation spectroscopy in magnetic fields
We perform saturated absorption spectroscopy on the D line for room
temperature rubidium atoms immersed in magnetic fields within the 0.05-0.13 T
range. At those medium-high field values the hyperfine structure in the excited
state is broken by the Zeeman effect, while in the ground state hyperfine
structure and Zeeman shifts are comparable. The observed spectra are composed
by a large number of absorption lines. We identify them as saturated
absorptions on two-level systems, on three-level systems in a V configuration
and on four-level systems in a N or double-N configuration where two optical
transitions not sharing a common level are coupled by spontaneous emission
decays. We analyze the intensity of all those transitions within a unified
simple theoretical model. We concentrate our attention on the double-N
crossovers signals whose intensity is very large because of the symmetry in the
branching ratios of the four levels. We point out that these structures,
present in all alkali atoms at medium-high magnetic fields, have interesting
properties for electromagnetically induced transparency and slow light
applications.Comment: Submitted to Physical Review
Light scalars coupled to photons and non-newtonian forces
A particle coupling to two photons couples also to charged particles,
like protons, through a loop. If the particle is a light scalar this induced
coupling to protons leads to non-newtonian forces. We show that the
experimental constraints on exotic, fifth-type forces lead to stringent
constraints on the coupling.Comment: With respect to v1, we have extended the paper, also new authors have
joined. Submitted to PR
Circular and linear magnetic birefringences in xenon at nm
The circular and linear magnetic birefringences corresponding to the Faraday
and the Cotton-Mouton effects, respectively, have been measured in xenon at
nm. The experimental setup is based on time dependent magnetic
fields and a high finesse Fabry-Perot cavity. Our value of the Faraday effect
is the first measurement at this wavelength. It is compared to theoretical
predictions. Our uncertainty of a few percent yields an agreement at better
than 1 with the computational estimate when relativistic effects are
taken into account. Concerning the Cotton-Mouton effect, our measurement, the
second ever published at nm, agrees at better than
with theoretical predictions. We also compare our error budget with those
established for other experimental published values
Finite size corrections to disordered Ising models on Random Regular Graphs
We derive the analytical expression for the first finite size correction to
the average free energy of disordered Ising models on random regular graphs.
The formula can be physically interpreted as a weighted sum over all non
self-intersecting loops in the graph, the weight being the free-energy shift
due to the addition of the loop to an infinite tree
Faraday and Cotton-Mouton Effects of Helium at nm
We present measurements of the Faraday and the Cotton-Mouton effects of
helium gas at \,nm. Our apparatus is based on an up-to-date
resonant optical cavity coupled to longitudinal and transverse magnetic fields.
This cavity increases the signal to be measured by more than a factor of
270\,000 compared to the one acquired after a single path of light in the
magnetic field region. We have reached a precision of a few percent both for
Faraday effect and Cotton-Mouton effect. Our measurements give for the first
time the experimental value of the Faraday effect at =\,1064\,nm. This
value is compatible with the theoretical prediction. Concerning Cotton-Mouton
effect, our measurement is the second reported experimental value at this
wavelength, and the first to agree at better than 1 with theoretical
predictions.Comment: Submitted to Phys. Rev.
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