This paper describes the 25 year effort to measure vacuum magnetic birefringence and dichroism with the PVLAS experiment. The experiment went through two main phases: the first using a rotating ...superconducting magnet and the second using two rotating permanent magnets. The experiment was not able to reach the predicted value from QED. Nonetheless the experiment has set the current best limits on vacuum magnetic birefringence and dichroism for a field of Bext=2.5 T, namely, Δn(PVLAS)=(12±17)×10−23 and |Δκ|(PVLAS)=(10±28)×10−23. The uncertainty on Δn(PVLAS) is about a factor 7 above the predicted value of Δn(QED)=2.5×10−23 @ 2.5 T.
The PVLAS collaboration is presently assembling a new apparatus (at the INFN section of Ferrara, Italy) to detect vacuum magnetic birefringence (VMB). VMB is related to the structure of the quantum ...electrodynamics (QED) vacuum and is predicted by the Euler-Heisenberg-Weisskopf effective Lagrangian. It can be detected by measuring the ellipticity acquired by a linearly polarized light beam propagating through a strong magnetic field. Using the very same optical technique it is also possible to search for hypothetical low-mass particles interacting with two photons, such as axion-like (ALP) or millicharged particles. Here we report the results of a scaled-down test setup and describe the new PVLAS apparatus. This latter is in construction and is based on a high-sensitivity ellipsometer with a high-finesse Fabry-Perot cavity (>4 × 105) and two 0.8 m long 2.5 T rotating permanent dipole magnets. Measurements with the test setup have improved, by a factor 2, the previous upper bound on the parameter Ae, which determines the strength of the nonlinear terms in the QED Lagrangian: A(PVLAS)e < 3.3 × 10−21 T−2 at 95% c.l. Furthermore, new laboratory limits have been put on the inverse coupling constant of ALPs to two photons and confirmation of previous limits on the fractional charge of millicharged particles is given.
We report on the resonant Fabry Perot cavity of the PVLAS (Polarization of the Vacuum with LASer) experiment operating at λ = 1064 nm with a record decay time of 2.7 ms, a factor more than two larger ...than any previously reported optical resonator. This corresponds to a coherence length of 8.1 · 10(5) m. The cavity length is 3.303 m, and the resulting finesse is 770,000.
The Southern Cone of South America (SCSA) is a key region for investigations about the peopling of the Americas. However, little is known about the eastern sector, the Argentinian Pampas. We analyzed ...18 mitochondrial genomes—7 of which are novel—from human skeletal remains from 3 Early to Late Holocene archaeological sites. The Pampas present a distinctive genetic makeup compared to other Middle to Late Holocene pre-Columbian SCSA populations. We also report the earliest individuals carrying SCSA-specific mitochondrial haplogroups D1j and D1g from Early and Middle Holocene, respectively. Using these deep calibration time points in Bayesian phylogenetic reconstructions, we suggest that the first settlers of the Pampas were part of a single and rapid dispersal ∼15,600 years ago. Finally, we propose that present-day genetic differences between the Pampas and the rest of the SCSA are due to founder effects, genetic drift, and a partial population replacement ∼9,000 years ago.
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•Analysis of 18 ancient human mitochondrial genomes from the Argentinian Pampas.•Genetic makeup of Early-Mid Holocene Pampas distinct from later neighboring peoples.•Earliest individuals carrying region-specific mitochondrial haplogroups D1j and D1g.•First Pampean settlers were part of a single and rapid dispersal ∼15,600 years ago.
Genetics; Genomics; Paleogenetics
This paper presents an inverse methodology with the aim to characterize a layered material through the identification of acoustical and mechanical properties of its layers. The framework to ...accomplish this objective is provided by the Inverse Problems (IPs) theory. Material characterization refers to the detection and localization of discontinuities, as well as to the identification of physical properties, in order to predict the material behaviour. In this particular case, the IP is solved in the form of a parameter estimation problem, in which the goal is the estimation of the characteristic acoustic impedance, transit time, and attenuation of each layer. These parameters are directly related to relevant material properties, such as the speed of sound, density, elastic modulus and elastic energy dissipation constants. The IP solution is obtained by minimizing a cost functional formulated as the least squares error between the waveform calculated using an equivalent model, and the measured waveform obtained from ultrasonic transmission tests. The applied methodology allowed the accurate estimation of the desired parameters in materials composed of up to three layers. As a second contribution, a power law frequency dependence of the wave attenuation was identified for several homogeneous materials, based on the same ultrasonic transmission experiments.
The distribution of certain rocks in the landscape allows us to reconstruct diverse aspects of past hunter-gatherer behavior. In this work, we evaluate the mobility patterns employed by these groups ...and the presence or absence of boundaries in the Aeolian system of the center of Argentina. To accomplish this objective, we consider two types of evidence: 1) raw material frequencies and distributions in three areas of this Aeolian System and 2) presence and frequency of knapping stones from Tandilia sources. We construct a fall-off curve that is based on the relationship between the frequency of an item and the distance to the source of supply. The characteristics of each area yielded the human groups that inhabited delineate different modes of exploitation of the rocks. The fall-off curve documents a steep drop-off between 300 and 350 km from the Tandilia source and the spatial analysis indicates that within this distance the source probably represents the threshold of direct access to the quarries. Tandilia stone-tools seem to systematically supply a relatively wide area of the Central Pampean Dunefields of the Pampa grasslands, through varied processes, but they arrive at very low frequencies over great distances. The presence of Tandilia rocks in the Western Pampean Dunefields and Western Pampas Sand Mantles and Dunefields indicates social interaction between human groups that shared some common technological knowledge. The presence of stones in the Central Pampean Dunefields coming from the xerophytic woodland of the Dry Pampas can be related with contacts and exchanges among the hunter-gatherer group that occupied different territories.
In this paper we report the status of the experiment MIR (Motion Induced Radiation), aimed at the experimental verification of the dynamical Casimir effect. The stringent theoretical requirements to ...observe the effect are satisfied in a scheme in which the conductivity of a semiconductor inside a superconducting microwave resonant cavity is varied in time. Free carriers in the semiconductor are periodically excited and recombine at 5 GHz. In this process vacuum and thermal photons are parametrically amplified in a time interval of 200-500 ns.
The PVLAS experiment aims at the observation and measurement of the effect of magnetic birefringence of vacuum (MBV) predicted by Quantum Electrodynamics. We describe here the new PVLAS apparatus ...which is currently being set up in INFN Ferrara. The apparatus features two rotating permanent dipole magnets and an ellipsometer operating under UHV with a high finesse Fabry–Perot cavity.
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