Physics Commons^™

Dissipative Macroscopic Quantum Tunneling In Type-I Superconductors, Ricardo Zarzuela, Eugene M. Chudnovsky, Javier Tejada

Publications and Research

We study macroscopic quantum tunneling of interfaces separating normal and superconducting regions in type-I superconductors. Mathematical model is developed, that describes dissipative quantum escape of a two-dimensional manifold from a planar potential well. It corresponds to, e.g., a current-driven quantum depinning of the interface from a grain boundary or from artificially manufactured pinning layer. Effective action is derived and instantons of the equations of motion are investigated. Crossover between thermal activation and quantum tunneling is studied and the crossover temperature is computed. Our results, together with recent observation of non-thermal low-temperature magnetic relaxation in lead, suggest possibility of a controlled …

Renormalization Of The Tunnel Splitting In A Rotating Nanomagnet, Michael F. O'Keeffe, Eugene M. Chudnovsky

Publications and Research

We study spin tunneling in a magnetic nanoparticle with biaxial anisotropy that is free to rotate about its anisotropy axis. Exact instanton of the coupled equations of motion is found that connects degenerate classical energy minima. We show that mechanical freedom of the particle renormalizes magnetic anisotropy and increases the tunnel splitting.

Constructing Local Bulk Observables In Interacting Ads/Cft, Daniel N. Kabat, Gilad Lifschytz, David A. Lowe

Publications and Research

Local operators in the bulk of AdS can be represented as smeared operators in the dual CFT. We show how to construct these bulk observables by requiring that the bulk operators commute at spacelike separation. This extends our previous work by taking interactions into account. Large-N factorization plays a key role in the construction. We show diagrammatically how this procedure is related to bulk Feynman diagrams.

Differential Microlensing Measurements Of Quasar Broad-Line Kinematics In Q2237+0305, Matthew J. O'Dowd, N F. Bate, R L. Webster, R Wayth

Publications and Research

The detailed workings of the central engines of powerful quasars remain a mystery. This is primarily due to the fact that, at their cosmological distances, the inner regions of these quasars are spatially unresolvable. Reverberation mapping is now beginning to unlock the physics of the Broad Emission Line Region (BELR) in nearby, low-luminosity quasars, however it is still unknown whether this gas is dominated by virial motion, by outflows, or infall. The challenge is greater for more distant, powerful sources due to the very long response time of the BELR to changes in the continuum. We present a new technique …

Quantum Entanglement Of A Tunneling Spin With Mechanical Modes Of A Torsional Resonator, Dmitry A. Garanin, Eugene M. Chudnovsky

Publications and Research

We solve Schr\"odinger equation describing a tunneling macrospin coupled to a torsional oscillator. Energy spectrum is studied for various quantum regimes. Magnetic susceptibility and noise spectrum are computed. We show that entanglement of the spin with mechanical modes of a subnanometer oscillator results in the decoherence of spin tunneling. For larger oscillators the presence of a tunneling spin can be detected through splitting of the mechanical mode at the resonance. Our results apply to experiments with magnetic molecules coupled to nanoresonators.

Quantum Tunneling Of The Interfaces Between Normal-Metal And Superconducting Regions Of A Type-I Pb Superconductor, Eugene M. Chudnovsky, S Velez, A Garcia-Santiago, J A. Hernandez

Publications and Research

Evidence of a non-thermal magnetic relaxation in the intermediate state of a type-I superconducor is presented. It is attributed to quantum tunneling of interfaces separating normal and superconducting regions. Tunneling barriers are estimated and temperature of the crossover from thermal to quantum regime is obtained from Caldeira-Leggett theory. Comparison between theory and experiment points to tunneling of interface segments of size comparable to the coherence length, by steps of order one nanometer.

Thermal Diffractive Corrections To Casimir Energies, Daniel N. Kabat, Dimitra Karabali

Publications and Research

We study the interplay of thermal and diffractive effects in Casimir energies. We consider plates with edges, oriented either parallel or perpendicular to each other, as well as a single plate with a slit. We compute the Casimir energy at finite temperature using a formalism in which the diffractive effects are encoded in a lower dimensional non-local field theory that lives in the gap between the plates. The formalism allows for a clean separation between direct or geometric effects and diffractive effects, and makes an analytic derivation of the temperature dependence of the free energy possible. At low temperatures, with …

Ssgss: The Spitzer-Sdss-Galex Spectroscopic Survey, Matthew J. O'Dowd, David Schiminovich, Benjamin D. Johnson, Marie A. Treyer

Publications and Research

The Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS) provides a new sample of 101 star-forming galaxies at z < 0.2 with unprecedented multi-wavelength coverage. New mid- to far-infrared spectroscopy from the Spitzer Space Telescope is added to a rich suite of previous imaging and spectroscopy, including ROSAT, Galaxy Evolution Explorer, Sloan Digital Sky Survey, Two Micron All Sky Survey, and Spitzer/SWIRE. Sample selection ensures an even coverage of the full range of normal galaxy properties, spanning two orders of magnitude in stellar mass, color, and dust attenuation. In this paper we present the SSGSS data set, describe the science drivers, and detail the sample selection, observations, data reduction, and quality assessment. Also in this paper, we compare the shape of the thermal continuum and the degree of silicate absorption of these typical, star-forming galaxies to those of starburst galaxies. We investigate the link between star formation rate, infrared luminosity, and total polycyclic aromatic hydrocarbon luminosity, with a view to calibrating the latter for spectral energy distribution models in photometric samples and at high redshift. Last, we take advantage of the 5-40 micron spectroscopic and far-infrared photometric coverage of this sample to perform detailed fitting of the Draine et al. dust models, and investigate the link between dust mass and star formation history and active galactic nucleus properties.

Tensorial Reconstruction At The Integrand Level, G. Heinrich, Giovanni Ossola, T. Reiter, F. Tramontano

Publications and Research

We present a new approach to the reduction of one-loop amplitudes obtained by reconstructing the tensorial expression of the scattering amplitudes. The reconstruction is performed at the integrand level by means of a sampling in the integration momentum. There are several interesting applications of this novel method within existing techniques for the reduction of one-loop multi-leg amplitudes: to deal with numerically unstable points, such as in the vicinity of a vanishing Gram determinant; to allow for a sampling of the numerator function based on real values of the integration momentum; to optimize the numerical reduction in the case of long …

Scattering Amplitudes From Unitarity-Based Reduction Algorithm At The Integrand-Level, P. Mastrolia, Giovanni Ossola, T. Reiter, F. Tramontano

Publications and Research

Samurai is a tool for the automated numerical evaluation of one-loop corrections to any scattering amplitudes within the dimensional-regularization scheme. It is based on the decomposition of the integrand according to the OPP-approach, extended to accommodate an implementation of the generalized d-dimensional unitarity-cuts technique, and uses a polynomial interpolation exploiting the Discrete Fourier Transform. samurai can process integrands written either as numerator of Feynman diagrams or as product of tree-level amplitudes. We discuss some applications, among which the 6- and 8-photon scattering in QED, and the 6-quark scattering in QCD. samurai has been implemented as a Fortran90 library, publicly available, …

On The Feasibility Of A Timely Transition To A More Sustainable Energy Future, Micha Tomkiewicz

Publications and Research

The paper uses the framework of the IPAT equation, as applied to CO2 emission, to decompose the various driving forces in the global energy use. Data from recent history are superimposed on projections of SRES IPCC scenarios to determine if enough sustainable capacity can be built to prevent irreversible ecological deterioration. The conclusion from the analysis is that, in agreement with the IPCC 4th report, until about 2030 there are no large differences between a sustainable scenario and the one that resembles “business as usual”. The sharp divergence that follows stems from different estimates in population growth and in the …

Rotational Doppler Effect In Magnetic Resonance, S Ledinez, Eugene M. Chudnovsky, Javier Tejada

Publications and Research

We compute the shift in the frequency of the spin resonance in a solid that rotates in the field of a circularly polarized electromagnetic wave. Electron spin resonance, nuclear magnetic resonance, and ferromagnetic resonance are considered. We show that contrary to the case of the rotating LC circuit, the shift in the frequency of the spin resonance has strong dependence on the symmetry of the receiver. The shift due to rotation occurs only when rotational symmetry is broken by the anisotropy of the gyromagnetic tensor, by the shape of the body, or by magnetocrystalline anisotropy. General expressions for the resonance …

Edges And Diffractive Effects In Casimir Energies, Daniel N. Kabat, Dimitra Karabali, V P. Nair

Publications and Research

The prototypical Casimir effect arises when a scalar field is confined between parallel Dirichlet boundaries. We study corrections to this when the boundaries themselves have apertures and edges. We consider several geometries: a single plate with a slit in it, perpendicular plates separated by a gap, and two parallel plates, one of which has a long slit of large width, related to the case of one plate being semi-infinite. We develop a general formalism for studying such problems, based on the wavefunctional for the field in the gap between the plates. This formalism leads to a lower dimensional theory defined …

Single Magnetic Molecule Between Conducting Leads: Effect Of Mechanical Rotations, Reem Jaafar, Eugene M. Chudnovsky, Dmitry A. Garanin

Publications and Research

We study spin-rotation effects in a magnetic molecule bridge d between two conducting leads. Dy- namics of the total angular momentum couples spin tunneling to the mechanical rotations. Landau- Zener spin transition produced by the time-dependent magne tic field generates a unique pattern of mechanical oscillations that can be detected by measuring t he electronic tunneling current through the molecule.

Dipolar Ordering In Crystals Of Mn12 Ac, Dmitry A. Garanin

Publications and Research

Ordering in realistic elongated box-shape crystals of the molecular magnet Mn_12 Ac is investigated with the site-resolved mean-field approximation that does not assume a uniform ordering. It is shown that ferromagnetic ordering should not occur in crystals with the aspect ratio up to 12. Instead, for the aspect ratio about 6, the inner and outer regions of the crystal order in different directions, uniformly along its length. Finding ordering temperature by extrapolating the inverse susceptibility curve does not provide a correct T_C.

Dynamical Decompactification And Three Large Dimensions, Brian Greene, Daniel N. Kabat, Stefanos Marnerides

Publications and Research

We study string gas dynamics in the early universe and seek to realize the Brandenberger - Vafa mechanism - a goal that has eluded earlier works - that singles out three or fewer spatial dimensions as the number which grow large cosmologically. Considering wound string interactions in an impact parameter picture, we show that a strong exponential suppression in the interaction rates for d > 3 spatial dimensions reflects the classical argument that string worldsheets generically intersect in at most four spacetime dimensions. This description is appropriate in the early universe if wound strings are heavy - wrapping long cycles - …

Deflagration With Quantum And Dipolar Effects In A Model Of A Molecular Magnet, Dmitry A. Garanin

Publications and Research

Combination of the thermal effet in magnetic deflagration with resonance spin tunneling controlled by the dipole-dipole interaction in molecular magnets leads to the increase of the deflagration speed in the dipolar window near tunneling resonances.

Interaction Of A Nanomagnet With A Weak Superconducting Link, Liufei Cai, Eugene M. Chudnovsky

Publications and Research

We study electromagnetic interaction of a nanomagnet with a weak superconducting link. Equations that govern coupled dynamics of the two systems are derived and investigated numerically. We show that the presence of a small magnet in the proximity of a weak link may be detected through Shapiro-like steps caused by the precession of the magnetic moment. Despite very weak magnetic field generated by the weak link, a time-dependent bias voltage applied to the link can initiate a non-linear dynamics of the nanomagnet that leads to the reversal of its magnetic moment. We also consider quantum problem in which a nanomagnet …

Rotational States Of Magnetic Molecules, Eugene M. Chudnovsky, Dmitry A. Garanin

Publications and Research

We study a magnetic molecule that exhibits spin tunneling and is free to rotate about its anisotropy axis. Exact low-energy eigenstates of the molecule that are superpositions of spin and rotational states are obtained. We show that parameter α=2(ℏS)2/(IΔ) determines the ground state of the molecule. Here ℏS is the spin, I is the moment of inertia, and Δ is the tunnel splitting. The magnetic moment of the molecule is zero at α<αc=[1−1/(2S)2]−1 and non-zero at α>αc. At α→∞ the spin of the molecule localizes in one of the directions along the anisotropy axis.

On The Casimir Interaction Between Holes In A Plate, Daniel N. Kabat, Dimitra Karabali, V P. Nair

Publications and Research

We study the leading long-distance attractive force between two holes in a plate arising from a scalar eld with Dirichlet boundary conditions on the plate. We use a formalism in which the interaction is governed by a non-local eld theory which lives on the two holes. The interaction energy is proportional to Q1Q2=r7 at large separation r, where Q1 and Q2 are certain charges associated with the holes. We compute these charges for round and rectangular holes. We show that the 1=r7 behavior is universal for separations large compared to the linear dimensions of the holes, irrespective of the spin …

The Hamiltonian Approach To Yang-Mills (2 + 1): Expansion Scheme And Corrections To String Tension, Dimitra Karabali, V P. Nair, Alexandr Yelinkov

Publications and Research

We carry out further analysis of the Hamiltonian approach to Yang-Mills theory in 2+1 dimensions which helps to place the calculation of the vacuum wave function and the string tension in the context of a systematic expansion scheme. The solution of the Schrodinger equation is carried out recursively. The computation of correlators is re-expressed in terms of a two-dimensional chiral boson theory. The effective action for this theory is calculated to first order in our expansion scheme and to the fourth order in a kinematic expansion parameter. The resulting corrections to the string tension are shown to be very small, …

Quantum Computing: Selected Internet Resources For Librarians, Researchers, And The Casually Curious, Jill Cirasella

Publications and Research

This article is an annotated selection of the most important and informative Internet resources for learning about quantum computing, finding quantum computing literature, and tracking quantum computing news.

Keeping Abreast Of Quantum News: Quantum Computing On The Web And In The Literature, Jill Cirasella

Publications and Research

This appendix describes tools that can help you track developments in quantum computing.

Historical Bibliography Of Quantum Computing, Jill Cirasella

Publications and Research

This bibliographic essay reviews seminal papers in quantum computing. Although quantum computing is a young science, its researchers have already published thousands of noteworthy articles, far too many to list here. Therefore, this appendix is not a comprehensive chronicle of the emergence and evolution of the field but rather a guided tour of some of the papers that spurred, formalized, and furthered its study.

Strokes Of Existence: The Connection Of All Things, Mari Gorman

Graduate Student Publications and Research

Acted or real—and all life is real whether one is acting or not—the common denominator and consistent, ubiquitous reality of life and all behavior is that it manifests in the form of relationships on all scales. But what is a relationship? Until now, the answer to this question has not been sufficiently known. As a result of many years of empirical research that began with the aim of discovering what is going on in a gifted actor when s/he is playing a character that can be observed and experienced as a living, intuitive being, and based on the knowledge that …

Vortices And Chaos In The Quantum Fluid, D. A. Wisniacki, E. R. Pujals, F. Borondo

Publications and Research

The motion of a single vortex originates chaos in the quantum fluid defined in Bohm's interpretation of quantum mechanics. Here we analize this situation in a very simple case: one single vortex in a rectangular billiard.

Applications Of Discoveries Range From Leveling Rice Fields To Anti-Terrorism Defenses, Aldemaro Romero Jr., Susan D. Allen

Publications and Research

No abstract provided.

Study Of Deconfinement In Na50, Paula Bordalo, M. C. Abreu, B. Alessandro, C. Alexa, R. Arnaldi, M. Atayan, C. Baglin, A. Baldit, M. Bedidian, S. Boelè, V. Boldea, Samuel Borenstein, C. Borges, A. Bussière, L. Capelli, C. Castagner, J. Castor, B. Chaurand, E. Chiavassa, C. Cicalò, T. Claudino, M. P. Comets, N. Constans, S. Constantinescu, P. Cortese, J. Cruz, A. De Falco, G. Dellacasa, N. De Marco, A. Devaux, S. Dita, O. Drapier, B. Espagnon, J. Fargeix, P. Force, M. Gallio, Y. K. Gavrilov, C. Gerschel, P. Giubellino, M. B. Golubeva, M. Gonin, A. A. Grigorian, J. Y. Grossiord, F. F. Guber, A. Guichard, H. Gulkanyan, R. Hakobyan, R. Haroutunian, M. Idzik, D. Jouan, T. L. Karavitcheva, L. Kluberg, A. B. Kurepin, Y Le Bornec, C. Lourenço, P. Macciotta, M. Mac Cormick, A. Marzari-Chiesa, M. Masera, A. Masoni, M. Monteno, M. Musso, P. Petiau, A. Piccotti, J. R. Pizzi, W. Prado Da Silva, F. Prino, G. Puddu, C. Quintans, L. Ramello, Laboratory Of Instrumentation And Experimental Particle Physics, L. Riccati, A. Romana, P. Saturnini, H. Santos, E. Scalas, E. Scomparin, S. Serci, R. Shahoyan, F. Sigaudo, S. Silva, M. Sitta, P. Sonderegger, X. Tarrago, N. S. Topilskaya, G. L. Usai, E. Vercellin, L. Villatte, N. Willis

Publications and Research

The J/Ψ production in 158 A Ge V Pb-Pb interactions is studied, in the dimuon decay channel, as a function of centrality, as measured with the electromagnetic or, alternatively, with the very forward hadronic calorimeters. After a first sharp variation at mid-centrality, both patterns continue to fall down and exhibit a curvature change at high centrality values. This trend excludes any conventional hadronic model and finds a natural explanation in a deconfined quark-gluon phase scenario.

Morphology And Photocatalysis Of Titanium Dioxide Aerogels, Sean Kelly

Dissertations, Theses, and Capstone Projects

Pollution of our environment has become one of the most serious problems of this century. Titanium dioxide aerogels is composed of nanocrystallites of TiO2 close-packed in roughly spherical mesospheres, which are agglomerated to form a highly-porous sponge. Aerogel morphology produces porosities of around 80% and surface area that can be as large as 1000 m2/g. The aerogels efficiently adsorb organic materials from the environment and when illuminated with UV light, decompose or oxidize the organic pollutants, ultimately to safe by-products such as CO2 and H 2O.

In this work we modify the synthetic conditions to produce aerogels with different morphologies …

Modal Properties And Spontaneous Emission Factor In Unstable-Resonator Semiconductor Lasers, Gang Yao

Dissertations, Theses, and Capstone Projects

An experimental study has been carried out on the spectral, modal, and dynamical properties of a monolithic unstable-resonator semiconductor laser. Due to the large loss and the non-power-orthogonal nature of the transverse and longitudinal modes in the unstable resonator, the spontaneous emission factor, defined as the ratio of the power of the spontaneous emission entering the lasing mode to the total power of the spontaneous emission, is much larger than that of a regular Fabry-Perot cavity of the same dimension. The large spontaneous emission factor has profound effects on the lasing properties. For a 100-{dollar}\mu{dollar}m-wide and 500-{dollar}\mu{dollar}m-long stripe-geometry unstable resonator …