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Laser-induced cooling of broadband heat reservoirs
https://cds.cern.ch/record/1995385
We explore, theoretically and experimentally, a method for cooling a broadband heat reservoir, via its laser-assisted collisions with two-level atoms followed by their fluorescence. This method is shown to be advantageous compared to existing laser-cooling methods in terms of its cooling efficiency, the lowest attainable temperature for broadband baths and its versatility: it can cool down any heat reservoir, provided the laser is red-detuned from the atomic resonance. It is applicable to cooling down both dense gaseous and condensed media.Gelbwaser-Klimovsky, DMon, 02 Mar 2015 06:29:52 GMThttps://cds.cern.ch/record/1995385Self-healing organic-dye-based random lasers
https://cds.cern.ch/record/1995383
One of the primary difficulties in the implementation of organic-dye-based random lasers is the tendency of organic dyes to irreversibly photodecay. In this letter we report the observation of "reversible" photodegradation in a Rhodamine 6G and ZrO$_2$ nanoparticle doped polyurethane random laser. We find that during degradation the emission broadens, redshifts, and decreases in intensity. After degradation the system is observed to self-heal leading to the emission returning to its pristine intensity, giving a recovery efficiency of 100%. While the peak intensity fully recovers, the process is not strictly "reversible" as the emission after recovery is still found to be broadened and redshifted. The combination of the peak emission fully recovering and the broadening of the emission leads to a remarkable result: the random laser cycled through degradation and recovery has a greater integrated emission intensity than the pristine system.Anderson, Benjamin RMon, 02 Mar 2015 06:29:52 GMThttps://cds.cern.ch/record/1995383Effect of experimental parameters on optimal transmission of light through opaque media
https://cds.cern.ch/record/1995381
Spatial light modulator (SLM) controlled transmission of light through opaque media is a relatively new experimental method with wide applications in various fields. While there has been a surge in research into the technique, there has been little work reported considering the effects of various experimental parameters on the efficiency of optimization. In this study, we explore the effects of various experimental conditions on optimization and find that the intensity enhancement depends on the number of modulated channels, number of phase steps, feedback integration radius, beam spot size, and active SLM area. We also develop a model, based on the propagation of a Gaussian beam with a random phase front, to account for most of the measured effects.Anderson, Benjamin RMon, 02 Mar 2015 06:29:52 GMThttps://cds.cern.ch/record/1995381Non-Perturbative Theory of Dispersion Interactions
https://cds.cern.ch/record/1995365
Some open questions exist with fluctuation-induced forces between extended dipoles. Conventional intuition derives from large-separation perturbative approximations to dispersion force theory. Here we present a full non-perturbative theory. In addition we discuss how one can take into account finite dipole size corrections. It is of fundamental value to investigate the limits of validity of the perturbative dispersion force theory.Boström, MMon, 02 Mar 2015 06:29:50 GMThttps://cds.cern.ch/record/1995365R\'enyi generalizations of quantum information measures
https://cds.cern.ch/record/1995346
Quantum information measures such as the entropy and the mutual information find applications in physics, e.g., as correlation measures. Generalizing such measures based on the R\'enyi entropies is expected to enhance their scope in applications. We prescribe R\'enyi generalizations for any quantum information measure which consists of a linear combination of von Neumann entropies with coefficients chosen from the set {-1,0,1}. As examples, we describe R\'enyi generalizations of the conditional quantum mutual information, some quantum multipartite information measures, and the topological entanglement entropy. Among these, we discuss the various properties of the R\'enyi conditional quantum mutual information and sketch some potential applications. We conjecture that the proposed R\'enyi conditional quantum mutual informations are monotone increasing in the R\'enyi parameter, and we have proofs of this conjecture for some special cases.Berta, MarioMon, 02 Mar 2015 06:29:19 GMThttps://cds.cern.ch/record/1995346Non-perturbative improvement and renormalization of the axial current in N_f=3 lattice QCD
https://cds.cern.ch/record/1995327
We report on a non-perturbative computation of the renormalization factor Z_A of the axial vector current in three-flavour O(a) improved lattice QCD with Wilson quarks and tree-level Symanzik improved gauge action and also recall our recent determination of the improvement coefficient c_A. Our normalization and improvement conditions are formulated at constant physics in a Schr\"odinger functional setup. The normalization condition exploits the full, massive axial Ward identity to reduce finite quark mass effects in the evaluation of Z_A and correlators with boundary wave functions to suppress excited state contributions in the pseudoscalar channel.Bulava, JohnMon, 02 Mar 2015 06:28:55 GMThttps://cds.cern.ch/record/1995327The Raychaudhuri equation for spinning test particles
https://cds.cern.ch/record/1995314
We obtain generalized Raychaudhuri equations for spinning test particles corresponding to congruences of particle's world-lines, momentum, and spin. These are physical examples of the Raychaudhuri equation for a non-normalized vector, unit time-like vector, and unit space-like vector. We compute and compare the evolution of expansion-like parameters associated with these congruences for spinning particles confined in the equatorial plane of the Kerr space-time.Mohseni, MortezaMon, 02 Mar 2015 06:27:45 GMThttps://cds.cern.ch/record/1995314James Webb Space Telescope segment phasing using differential optical transfer functions
https://cds.cern.ch/record/1995306
Differential Optical Transfer Function (dOTF) is an image-based, non-iterative wavefront sensing method that uses two star images with a single small change in the pupil. We describe two possible methods for introducing the required pupil modification to the JWST, one using a small (<lambda/4) displacement of a single segment's actuator and another that uses small misalignments of NIRCam's filter wheel. While both methods should work with NIRCam, the actuator method will allow both MIRI and NIRISS to be used for segment phasing, which is new functionality. Since the actuator method requires only small displacements, it should provide a fast and safe phasing alternative that reduces mission risk and can be performed frequently for alignment monitoring and maintenance. Since a single actuator modification can be seen by all three cameras, it should be possible to calibrate the non-common-path aberrations between them. Large segment discontinuities can be measured using dOTFs in two filter bands. Using two images of a star field, aberrations along multiple lines of sight through the telescope can be measured simultaneously. Also, since dOTF gives the pupil field amplitude as well as phase, it could provide a first approximation or constraint to the planned iterative phase retrieval algorithms.Codona, Johanan LMon, 02 Mar 2015 06:27:28 GMThttps://cds.cern.ch/record/1995306A theoretical room-temperature line list for 15NH3
https://cds.cern.ch/record/1995303
A new room temperature line list for $^{15}$NH$_3$ is presented. This line list comprised of transition frequencies and Einstein coefficients has been generated using the `spectroscopic' potential energy surface NH3-Y2010 and an ab initio dipole moment surface. The $^{15}$NH$_3$ line list is based on the same computational procedure used for the line list for $^{14}$NH$_3$ BYTe reported recently and should be as accurate. Comparisons with experimental frequencies and intensities are presented. The synthetic spectra show excellent agreement with experimental spectra.Yurchenko, Sergei NMon, 02 Mar 2015 06:27:27 GMThttps://cds.cern.ch/record/1995303Test of the string loop oscillation model using kHz quasiperiodic oscillations in a neutron star binary
https://cds.cern.ch/record/1995293
The model of current-carrying string loop oscillations is tested to explain the special set of frequencies related to the high-frequency quasiperiodic oscillations (HF QPOs) observed recently in the low-mass X-ray binary XTE J1701-407 containing a neutron star. The external geometry of the neutron star is approximated by the Kerr geometry, introducing errors not exceeding $10~\%$ for slowly rotating massive neutron stars. The frequencies of the radial and vertical string loop oscillations are then governed by the mass $M$ and dimensionless spin $a$ of the neutron star, and by the dimensionless parameter $\omega$ describing combined effects of the string loop tension and its angular momentum. It is explicitly demonstrated that the string-loop oscillation model can explain the observed kHz frequencies for the neutron star parameters restricted to the intervals ${0.2<a<0.4}$ and ${2.1<M/{\rm M}_{\odot}<2.5}$. However, the stringy parameter $\omega$ cannot be the same for all the three HF QPO observations in the XTE J1701-407 source; the limits on the acceptable values of $\omega$ are given in dependence on the spacetime parameters $M$ and $a$.Stuchlík, ZdeněkMon, 02 Mar 2015 06:27:27 GMThttps://cds.cern.ch/record/1995293Stability of Hartmann flow with the convective approximation
https://cds.cern.ch/record/1995198
This research is focused on linear analysis of a plane-parallel flow stability in a transverse magnetic field (Hartmann flow) within a convective approximation. We derive and solve equations describing the perturbation growth. Perturbation modes and their nonexcitation conditions have been determined. An equation for the instability increment has been derived and it is shown that the equation has an unstable root. Additionally, we show that the resulting instabilities qualitatively agree with the experimental data.Kalashnikov, I YuSat, 28 Feb 2015 07:51:50 GMThttps://cds.cern.ch/record/1995198Review of Some Promising Fractional Physical Models
https://cds.cern.ch/record/1995197
Fractional dynamics is a field of study in physics and mechanics investigating the behavior of objects and systems that are characterized by power-law non-locality, power-law long-term memory or fractal properties by using integrations and differentiation of non-integer orders, i.e., by methods of the fractional calculus. This paper is a review of physical models that look very promising for future development of fractional dynamics. We suggest a short introduction to fractional calculus as a theory of integration and differentiation of non-integer order. Some applications of integro-differentiations of fractional orders in physics are discussed. Models of discrete systems with memory, lattice with long-range inter-particle interaction, dynamics of fractal media are presented. Quantum analogs of fractional derivatives and model of open nano-system systems with memory are also discussed.Tarasov, Vasily ESat, 28 Feb 2015 07:51:50 GMThttps://cds.cern.ch/record/1995197Monitoring and optimization of energy consumption of base transceiver stations
https://cds.cern.ch/record/1995194
The growth and development of the mobile phone network has led to an increased demand for energy by the telecommunications sector, with a noticeable impact on the environment. Monitoring of energy consumption is a great tool for understanding how to better manage this consumption and find the best strategy to adopt in order to maximize reduction of unnecessary usage of electricity. This paper reports on a monitoring campaign performed on six Base Transceiver Stations (BSs) located central Italy, with different technology, typology and technical characteristics. The study focuses on monitoring energy consumption and environmental parameters (temperature, noise, and global radiation), linking energy consumption with the load of telephone traffic and with the air conditioning functions used to cool the transmission equipment. Moreover, using experimental data collected, it is shown, with a Monte Carlo simulation based on power saving features, how the BS monitored could save energy.Spagnuolo, AntonioSat, 28 Feb 2015 07:51:50 GMThttps://cds.cern.ch/record/1995194Relativistic Remnants of Non-Relativistic Electrons
https://cds.cern.ch/record/1995193
Electrons obeying the Dirac equation are investigated under the non-relativistic $c \mapsto \infty$ limit. General solutions are given by derivatives of the relativistic invariant functions whose forms are different in the time- and the space-like region, yielding the delta function of $(ct)^2 - x^2$. This light-cone singularity does survive to show that the charge and the current density of electrons travel with the speed of light in spite of their massiveness.Kashiwa, TaroSat, 28 Feb 2015 07:51:50 GMThttps://cds.cern.ch/record/1995193Entropy of finite random binary sequences with weak long-range correlations
https://cds.cern.ch/record/1995168
We study the N-step binary stationary ergodic Markov chain and analyze its differential entropy. Supposing that the correlations are weak we express the conditional probability function of the chain through the pair correlation function and represent the entropy as a functional of the pair correlator. Since the model uses the two-point correlators instead of the block probability, it makes it possible to calculate the entropy of strings at much longer distances than using standard methods. A fluctuation contribution to the entropy due to finiteness of random chains is examined. This contribution can be of the same order as its regular part even at the relatively short lengths of subsequences. A self-similar structure of entropy with respect to the decimation transformations is revealed for some specific forms of the pair correlation function. Application of the theory to the DNA sequence of the R3 chromosome of Drosophila melanogaster is presented.Melnik, S SSat, 28 Feb 2015 07:51:48 GMThttps://cds.cern.ch/record/1995168Observation of the nuclear magnetic octupole moment of $^{173}$Yb from precise measurements of hyperfine structure in the ${^3P}_2$ state
https://cds.cern.ch/record/1995164
We measure hyperfine structure in the metastable ${^3P}_2$ state of $^{173}$Yb and extract the nuclear magnetic octupole moment. We populate the state using dipole-allowed transitions through the ${^3P}_1$ and ${^3S}_1$ states. We measure frequencies of hyperfine transitions of the ${^3P}_2 \rightarrow {^3S}_1$ line at 770 nm using a Rb-stabilized ring cavity resonator with a precision of 200 kHz. Second-order corrections due to perturbations from the nearby ${^3P}_1$ and ${^1P}_1$ states are below 30 kHz. We obtain the hyperfine coefficients as: $A=-742.11(2)$ MHz, $B=1339.2(2)$ MHz, which represent two orders-of-magnitude improvement in precision, and $C=0.54(2)$ MHz. From atomic structure calculations, we obtain the nuclear moments: quadrupole $Q=2.46(12)$ b and octupole $\Omega=-34.4(21)$ b\,$\times \mu_N$.Singh, Alok KSat, 28 Feb 2015 07:51:47 GMThttps://cds.cern.ch/record/1995164Constraints on axion and corrections to Newtonian gravity from the Casimir effect
https://cds.cern.ch/record/1995133
Axion is a light pseudoscalar particle of much interest for physics of elementary particles and for astrophysics. We review the recently obtained constraints on axion to nucleon coupling constants following from different experiments on measuring the Casimir interaction. These constraints are compared with those following from other laboratory experiments within the wide range of masses of axion-like particles from 10^{-10} to 20 eV. We also collect the most strong constraints on the Yukawa-type and power-type corrections to the Newton law of gravitation which follow from measurements of the Casimir interaction, Eotvos- and Cavendish-type experiments. The possibility to obtain stronger constraints on an axion from the Casimir effect is proposed.Klimchitskaya, G LSat, 28 Feb 2015 07:50:28 GMThttps://cds.cern.ch/record/1995133Hamilton-Jacobi Formalism for Tachyon Inflation
https://cds.cern.ch/record/1995118
Tachyon inflation is reconsidered by using the recent observational data obtained from Planck-2013 and BICEP2. The Hamilton-Jacobi formalism is picked out as a desirable approach in this work, which allows one to easily obtain the main parameters of the model. The Hubble parameter is supposed as a power-law and exponential function of the scalar field, and each case is considered separately. The constraints on the model, which come from observational data, are explained during the work. The results show a suitable value for the tensor spectral index and an appropriate form of the potential.Aghamohammadi, ASat, 28 Feb 2015 07:48:51 GMThttps://cds.cern.ch/record/1995118Gravitational Casimir effect
https://cds.cern.ch/record/1995113
We derive the gravitonic Casimir effect with non-idealised boundary conditions. This allows the quantification of the gravitonic contribution to the Casimir effect from real bodies. We quantify the meagreness of the gravitonic Casimir effect in ordinary matter. We also quantify the enhanced effect produced by the speculated Heisenberg-Couloumb (H-C) effect in superconductors, thereby providing a test for the validity of the H-C theory, and consequently the existence of gravitons.Quach, James QSat, 28 Feb 2015 07:48:51 GMThttps://cds.cern.ch/record/1995113Elliptical Solutions to the Standard Cosmology Model with Realistic Values of Matter Density
https://cds.cern.ch/record/1995104
We have examined a solution to the FRW model of the Einstein and de Sitter Universe, often termed the standard model of cosmology, using wide values for the normalized cosmological constant Omega_L and spacetime curvature Omega_k with proposed values of normalized matter density. These solutions were evaluated using a combination of the third type of elliptical equations and were found to display critical points for redshift z, between 1 and 3, when Omega_L is positive. These critical points occur at values for normalized cosmological constant higher than those currently thought important, though we find this solution interesting because the Omega_L term may increase in dominance as the Universe evolves bringing this discontinuity into importance. We also find positive Omega_L tends towards attractive at values of z which are commonly observed for distant galaxies.Oztas, Ahmet MecitSat, 28 Feb 2015 07:47:45 GMThttps://cds.cern.ch/record/1995104An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
https://cds.cern.ch/record/1995077
So far, roughly 40 quasars with redshifts greater than z=6 have been discovered. Each quasar contains a black hole with a mass of one billion solar masses ( $10^9 M_\odot$). The existence of such black holes when the Universe was less than 1 billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies. Here we report the discovery of an ultra-luminous quasar, SDSS J010013.02+280225.8, at redshift z=6.30. It has an optical and near-infrared luminosity a few times greater than those of previously known z>6 quasars. On the basis of the deep absorption trough on the blue side of the Ly $\alpha$ emission line in the spectrum, we estimate the proper size of the ionized proximity zone associated with the quasar to be 26 million light years, larger than found with other z>6.1 quasars with lower luminosities. We estimate (on the basis of a near-infrared spectrum) that the black hole has a mass of $\sim 1.2 \times 10^{10} M_\odot$, which is consistent with the $1.3 \times 10^{10} M_\odot$ derived by assuming an Eddington-limited accretion rate.Wu, Xue-BingSat, 28 Feb 2015 07:47:42 GMThttps://cds.cern.ch/record/1995077Evaluating Multi-Gigabit Transceivers (MGT) for Use in High Energy Physics Through Proton Irradiation.
https://cds.cern.ch/record/1995019
The paper summarizes the radiation test results of Xilinx 7-Series Multi-Gigabit Transceivers (MGT) operating in a 180 MeV proton beam to test their suitability in High Energy Physics experiments.Wirthlin, MFri, 27 Feb 2015 14:01:47 GMThttps://cds.cern.ch/record/1995019Characterization results and first applications of KLauS - an ASIC for SiPM charge and fast discrimination readout
https://cds.cern.ch/record/1994822
KLauS is an ASIC produced in the AMS 0.35μm
SiGe technology to read out the charge signals from silicon
photomultipliers. Developed as an analog front end for future
calorimeters with high granularity as pursued by the AHCAL
concept in the CALICE collaboration, the ASIC is supposed to
measure the charge signal of the sensors in a large dynamic
range and with a high precision. In order to compensate bias
and temperature fluctuations of each sensor individually, an 8-bit
DAC to tune the voltage at the input terminal is implemented.
Using an integrated fast comparator with low jitter, the time
information can be measured with sub-nanosecond resolution.
The low power consumption of the ASIC can be further decreased
using power gating techniques. Future versions of KLauS
are under development and will incorporate an ADC with a
resolution of up to 12 bit together with blocks for digital data
transmission. Most recent characterization results for the KLauS
chip are presented as well as results from a KLauS-based test
setup developed for mass characterization of scintillator tiles used
in the AHCAL test beam program.Briggl, KThu, 26 Feb 2015 09:45:02 GMThttps://cds.cern.ch/record/1994822KLauS - A Charge Readout and Fast Discrimination Readout ASIC for Silicon Photomultipliers
https://cds.cern.ch/record/1994820
KLauS is an application specific integrated circuit (ASIC) for the readout of silicon
photomultipliers. The chip has been designed for the application in the analog hadronic calorimeter developed by the CALICE collaboration for the next linear collider experiment . To address the severe power constraints introduced by the highly granular design of the calorimeter, the chip has been designed for low power consumption while maintaining the high dynamic range and timing precision required by the experiment. In addition, a power gating scheme has been implemented to further decrease the average power consumption. For a duty cycle of 1% a value of 25mW per channel is achieved without affecting the readout capabilities of the chip. The chip has been designed in the 0:35mm SiGe technology and provides a low power readout channel for SiPMs with low gain for the input stage of the existing readout chip SPIROC. The analog channel of KLauS will be implemented in a future version of the SPIROC chip.Dorn, MThu, 26 Feb 2015 09:40:56 GMThttps://cds.cern.ch/record/1994820Simulation of Silicon Photomultipliers
https://cds.cern.ch/record/1994819
We present a software framework for the simulation of Silicon Photomultipliers (SiPM). The
simulation provides a detailed model of the SiPM response to arbitrary light pulses, depending
on the basic SiPM characteristics which have to be determined by measurements. The simulation was validated for a S10362-11-100C Hamamatsu MPPC in the whole dynamic range and was used to study the contribution of different noise sources to the response and photon-counting resolution.Eckert, PThu, 26 Feb 2015 09:34:35 GMThttps://cds.cern.ch/record/1994819