Simulation of Supersymmetric Models with a Local Nicolai Map

We study the numerical simulation of supersymmetric models having a local Nicolai map. The mapping can be regarded as a stochastic equation and its numerical integration provides an algorithm for the simulation of the original model. In this paper, the method is discussed in details and applied to examples in 0+1 and 1+1 dimensions.Comment: 18 pages, REVTeX + 2 PostScript figure

Perturbative and Numerical Methods for Stochastic Nonlinear Oscillators

Interferometric gravitational wave detectors are devoted to pick up the effect induced on masses by gravitational waves. The variations of the length dividing two mirrors is measured through a laser interferometric technique. The Brownian motion of the masses related to the interferometer room temperature is a limit to the observation of astrophysical signals. It is referred to as thermal noise and it affects the sensitivity of both the projected and the future generation interferometers. In this paper we investigate the relevance of small non-linear effects and point out their impact on the sensitivity curve of interferometric gravitational wave detectors (e.g. VIRGO, LIGO, GEO, ...) through perturbative methods and numerical simulations. We find that in the first order approximation the constants characterizing the power spectrum density (PSD) are renormalized but it retains its typical shape. This is due to the fact that the involved Feynman diagrams are of tadpole type. Higher order approximations are required to give rise to up-conversion effects. This result is predicted by the perturbative approach and is in agreement with the numerical results obtained by studying the system's non-linear response by numerically simulating its dynamics.Comment: 12 pages, REVTeX + 7 PostScript figure

Free-space quantum key distribution by rotation-invariant twisted photons

Twisted photons are photons carrying a well-defined nonzero value of orbital angular momentum (OAM). The associated optical wave exhibits a helical shape of the wavefront (hence the name) and an optical vortex at the beam axis. The OAM of light is attracting a growing interest for its potential in photonic applications ranging from particle manipulation, microscopy and nanotechnologies, to fundamental tests of quantum mechanics, classical data multiplexing and quantum communication. Hitherto, however, all results obtained with optical OAM were limited to laboratory scale. Here we report the experimental demonstration of a link for free-space quantum communication with OAM operating over a distance of 210 meters. Our method exploits OAM in combination with optical polarization to encode the information in rotation-invariant photonic states, so as to guarantee full independence of the communication from the local reference frames of the transmitting and receiving units. In particular, we implement quantum key distribution (QKD), a protocol exploiting the features of quantum mechanics to guarantee unconditional security in cryptographic communication, demonstrating error-rate performances that are fully compatible with real-world application requirements. Our results extend previous achievements of OAM-based quantum communication by over two orders of magnitudes in the link scale, providing an important step forward in achieving the vision of a worldwide quantum network

On the Analytic Structure of a Family of Hyperboloidal Beams of Potential Interest for Advanced LIGO

For the baseline design of the advanced Laser Interferometer Gravitational-wave Observatory (LIGO), use of optical cavities with non-spherical mirrors supporting flat-top ("mesa") beams, potentially capable of mitigating the thermal noise of the mirrors, has recently drawn a considerable attention. To reduce the severe tilt-instability problems affecting the originally conceived nearly-flat, "Mexican-hat-shaped" mirror configuration, K. S. Thorne proposed a nearly-concentric mirror configuration capable of producing the same mesa beam profile on the mirror surfaces. Subsequently, Bondarescu and Thorne introduced a generalized construction that leads to a one-parameter family of "hyperboloidal" beams which allows continuous spanning from the nearly-flat to the nearly-concentric mesa beam configurations. This paper is concerned with a study of the analytic structure of the above family of hyperboloidal beams. Capitalizing on certain results from the applied optics literature on flat-top beams, a physically-insightful and computationally-effective representation is derived in terms of rapidly-converging Gauss-Laguerre expansions. Moreover, the functional relation between two generic hyperboloidal beams is investigated. This leads to a generalization (involving fractional Fourier transform operators of complex order) of some recently discovered duality relations between the nearly-flat and nearly-concentric mesa configurations. Possible implications and perspectives for the advanced LIGO optical cavity design are discussed.Comment: 9 pages, 6 figures, typos corrected, Eqs. (24) and (26) change

Natural Volterra Runge-Kutta methods

A very general class of Runge-Kutta methods for Volterra integral equations of the second kind is analyzed. Order and stage order conditions are derived for methods of order p and stage order q = p up to the order four. We also investigate stability properties of these methods with respect to the basic and the convolution test equations. The systematic search for A- and V0-stable methods is described and examples of highly stable methods are presented up to the order p = 4 and stage order q = 4

Long telomeric C-rich 5'-tails in human replicating cells.

Telomeres protect the ends of linear chromosomes from abnormal recombination events and buffer them against terminal DNA loss. Models of telomere replication predict that two daughter molecules have one end that is blunt, the product of leading-strand synthesis, and one end with a short G-rich 3′-overhang. However, experimental data from proliferating cells are not completely consistent with this model. For example, telomeres of human chromosomes have long G-rich 3′-overhangs, and the persistence of blunt ends is uncertain. Here we show that the product of leading-strand synthesis is not always blunt but can contain a long C-rich 5′-tail, the incompletely replicated template of the leading strand. We examined the presence of G-rich and C-rich single-strand DNA in fibroblasts and HeLa cells. Although there were no significant changes in the length distribution of the 3′-overhang, the 5′-overhangs were mostly present in S phase. Similar results were obtained using telomerase-negative fibroblasts. The amount and the length distribution of the 5′ C-rich tails strongly correlate with the proliferative rate of the cell cultures. Our results suggest that, contrary to what has commonly been supposed, completion of leading-strand synthesis is inefficient and could well drive telomere shortening

Fifty Years of PMV Model: Reliability, Implementation and Design of Software for Its Calculation

In most countries, PMV is the reference index for the assessment of thermal comfort conditions in mechanically conditioned environments. It is also the basis to settle input values of the operative temperature for heating and cooling load calculations, sizing of equipment, and energy calculations according to EN 16798-1 and 16798-2 Standards. Over the years, great effort has been spent to study the reliability of PMV, whereas few investigations were addressed to its calculation. To study this issue, the most significant apps devoted to its calculation have been compared with a reference software compliant with EN ISO 7730 and the well-known ASHRAE Thermal Comfort Tool. It has been revealed that only few apps consider all six variables responsible for the thermal comfort. Relative air velocity is not considered by ASHRAE Thermal Comfort Tool and, finally, the correction of basic insulation values due to body movements introduced by EN ISO 7730 and EN ISO 9920 Standards has only been considered in one case. This implies that most software and apps for the calculation of PMV index should be used with special care, especially by unexperienced users. This applies to both research and application fields

On-board centralized system tor regulating the pressure of the tyres of a motor-vehicle

An on-board centralized system for regulating the pressure of the tyres of a motor-vehicle. Tue system comprises a source of pressurized air (lOl), two toroidal pneumatic rotary joints (T) each associated to a driving wheel (W) ofthe motor-vehicle, and a circuit that sets in communication the source of pressurized air (I O l) with an inlet fitting of each pneumatic rotary joint (T). Tue output member of the constant-velocity joint (J) and the wheel spindle (7) have an internal duct (65) for passage of air, connected on one side to the respective pneumatic rotary joint (T) and on the other side to a plenum (P) of the respective driving wheel (W). Each non-driving wheel (WR) has its wheel spindle ( 46) traversed by an axial bare for the passage of air, connected on one side to the air-supply circuit via a pneumatic rotary joint (TR) and on the other side to a plenum (PR) of the non-driving wheel (WR), which is in turn connected to the inner chamber (C) of the tyre. Each driving wheel or non-driving wheel has its plenum (P, PR) connected to the inner chamber (C) of the tyre via two parallel lines (L2, L3), for deflating and inflating, respectively, the tyre interposed in which are respective one-way valves (28, 32). Tue one-way valve (28) on the deflation line is provided with a return spring (30), which guarantees a pre-set minimum value of he pressure of the inner chamber (C) of the tyre