Physical Sciences and Mathematics Commons^™

Scaling In One-Dimensional Localized Absorbing Systems, Lev I. Deych, Alexey Yamilov, Alexander A. Lisyansky

Physics Faculty Research & Creative Works

Numerical study of the scaling of transmission fluctuations in the one-dimensional localization problem in the presence of absorption is carried out. Violations of single-parameter scaling for lossy systems are found and explained on the basis of a new criterion for different types of scaling behavior derived by Deych et al.

Phonon Modes In Inas Quantum Dots, Shang-Fen Ren, G Qin, Deyu Lu

Faculty publications – Physics

Phonon modes in spherical InAs quantum dots (QDs) with up to 11 855 atoms (about 8.5 nm in diameter) are calculated by using a valence force field model, and all the vibration frequencies and vibration amplitudes of the QDs are calculated directly from the lattice-dynamic matrix. The projection operators of the irreducible representations of the group theory are employed to reduce the computational intensity, which further allows us to investigate the quantum confinement effect of phonon modes with different symmetries. It is found that the size effects of phonon modes depend on the symmetry of the modes. For zinc-blende structure, …

In-Situ Spectroscopic Studies Of Electronic Processes In Buckminsterfullerene Thin Films, Gordon Chambers

Doctoral

This study attempts to develop an understanding of the electronic processes active within the solid state of C60. The emphasis throughout the work has been upon the generation and spectroscopic identification of any species, which could potentially contribute to electronic conduction in thin films of C60. The relative importance of these inter-and intramolecular processes in terms of their contribution to the electronic transport is discussed through the comparison of the properties of the molecule with the properties of the bulk solid

Initially the low intensity optical properties of the C60 molecule in solution and in solid were assessed. Vibrational spectroscopy …

Velocity Field Distributions Due To Ideal Line Vortices, Thomas D. Levi, David C. Montgomery

Dartmouth Scholarship

We evaluate numerically the velocity field distributions produced by a bounded, two-dimensional fluid model consisting of a collection of parallel ideal line vortices. We sample at many spatial points inside a rigid circular boundary. We focus on “nearest-neighbor” contributions that result from vortices that fall (randomly) very close to the spatial points where the velocity is being sampled. We confirm that these events lead to a non-Gaussian high-velocity “tail” on an otherwise Gaussian distribution function for the Eulerian velocity field. We also investigate the behavior of distributions that do not have equilibrium mean-field probability distributions that are uniform inside the …

Large-Scale Synchrony In Weakly Interacting Automata, Eric J. Friedman, Adam S. Landsberg

WM Keck Science Faculty Papers

We study the behavior of two spatially distributed (sandpile) models which are weakly linked with one another. Using a Monte Carlo implementation of the renormalization-group and algebraic methods, we describe how large-scale correlations emerge between the two systems, leading to synchronized behavior.

Effects Of Relativity On The Time-Resolved Tunneling Of Electron Wave Packets, P Krekora, Q Su, Rainer Grobe

Faculty publications – Physics

We solve numerically the time-dependent Dirac equation for a quantum wave packet tunneling through a potential barrier. We analyze the spatial probability distribution of the transmitted wave packet in the context of the possibility of effectively superluminal peak and front velocities of the electron during tunneling. Both the Dirac and Schrodinger theories predict superluminal tunneling speeds. However, in contrast to the Dirac theory the Schrodinger equation allows a possible violation of causality. Based on an analysis of the tunneling process in full temporal and spatial resolution, we introduce an instantaneous tunneling speed that can be computed inside the potential barrier.

Boolean Functions With Important Cryptographic Properties., Subhamoy Maitra Dr.

Doctoral Theses

In this thesis we concentrate on properties of cryptographically significant Boolean functions.The techniques are mainly combinstorial and provide new resulta on enumeration and construction of such functions. Initially we concentrate on a partieular subset of Boolean functions called the symmetric Boolean functions. A closed form expression for the Walsh transform of an arbitrary symmetric Boolean function is presented. We completely characterize the symmetric functions with maximum nonlinearity and show that the maximum nonlinearity of n-variable symmetrie function can be 2n-1-2[n-1l2], Moreover, new classes of symmetric balanced and symmetric correlation immune functions are considered.We provide a randomised heuristic to construct balanced …

Neutrino Reactions On The Deuteron, S. Nakamura, T. Sato, Vladimir Gudkov, K. Kubodera

Faculty Publications

The cross sections for the ν-d and ν̅ -d reactions are calculated for incident energy up to E_ν=170 MeV with the use of a phenomenological Lagrangian approach. We assess and improve the reliability of the employed calculational method by examining the dependence of the results on various input and approximations that go into the calculation. The main points of improvement over the existing work are (1) use of the “modern” NN potentials, (2) use of the more accurate nucleon weak-interaction form factors, and (3) monitoring the strength of a vertex that governs the exchange-current contribution, with the use …

Diamagnetic Persistent Current In Diffusive Normal-Metal Rings, E. M.Q. Jariwala, P. Mohanty, M. B. Ketchen, Richard A. Webb

Faculty Publications

We have measured a diamagnetic persistent current with flux periodicities of both h/e and h/2e in an array of thirty diffusive mesoscopic gold rings. At the lowest temperatures, the magnitudes of the currents per ring corresponding to the h/e- and h/2e-periodic responses are both comparable to the Thouless energy E_c≡ħ/τ_D, where τ_D is the diffusion time. Taken in conjunction with earlier experiments, our results strongly challenge the conventional theories of persistent current. We consider a new approach associated with the saturation of …

Spectral Equivalence Of Bosons And Fermions In One-Dimensional Harmonic Potentials, Michael Crescimanno, Adam S. Landsberg

WM Keck Science Faculty Papers

Recently, Schmidt and Schnack [Physica A 260, 479 (1998)], following earlier references, reiterate that the specific heat of N noninteracting bosons in a one-dimensional harmonic well equals that of N noninteracting fermions in the same potential. We show that this peculiar relationship between heat capacities results from a more dramatic equivalence between Bose and Fermi systems. Namely, we prove that the excitations of such Bose and Fermi systems are spectrally equivalent. Two complementary proofs of this equivalence are provided; one based on a combinatoric argument, the other from analysis of the underlying dynamical symmetry group.

Dirac Theory Of Ring-Shaped Electron Distributions In Atoms, P Krekora, R E. Wagner, Q Su, Rainer Grobe

Faculty publications – Physics

The time-dependent Dirac equation is solved numerically on a space-time grid for an atom in a strong static magnetic field and a laser field. The resonantly induced relativistic motion of the atomic electron leads to a ringlike spatial probability density similar to the features that have been recently predicted [Wagner, Su, and Grobe, Phys. Rev. Lett. 84, 3282 (2000)] based on a phase-space method. We further demonstrate that spin-orbit coupling for a fast-moving electron in such an atom becomes significant and the time dependence of the spin can dephase even if initially aligned parallel to the direction of the static …

Significance Of The Sagnac Effect, Pal R. Molnar

Pal R. Molnar

During the historical development, the notions of electrodynamics and the theory light have become complicated complexes of concepts [1]. And what is more, nowadays they are wholly confused. The laws of electrodynamics in present form are not valid in rotating and deforming systems [2]. These turbulent notion-complexes -of which inadequacy to the inner connections are verified by experiments, measurements results, as well as certain electrodynamical states and processes- have to be broken open, disintegrated, then disjoined. Henceforth, we must search those genuine, pure and simple electrodynamical ideas, which can already join in the immanent natural well and adequate manner. Consequently, …

Higher Twist Corrections And Maxima For Dis On A Proton In The High Density Qcd Region, E. Gotsman, Eugene Levin, U. Maor, L. Mclerran, Kirill Tuchin

Kirill Tuchin

We show that the ratio of different structure functions have a maximum which depends on energy. We argue, using the Golec-Biernat and Wusthoff model as well as the eikonal approach, that these maxima are functions of the saturation scale. We analyze leading and higher twist contributions for different observables to check whether a kinematic region exists where high parton density effects can be detected experimentally.

Electroproduction Of The Λ(1520) Hyperon, M. Bektasoglu, G. E. Dodge, T. A. Forest, C. E. Hyde-Wright, S. E. Kuhn, R. A. Niyazov, L. B. Weinstein, Et Al., The Clas Collaboration

Physics Faculty Publications

The reaction e^→pe′K⁺Λ(1520) with Λ(1520)→p′K⁻ was studied at electron beam energies of 4.05, 4.25, and 4.46 GeV, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cos θ_K+, φ_K+, Q², and W dependencies of Λ(1520) electroproduction are presented for the kinematic region 0.9 < Q² < 2.4 GeV² and 1.95 < W < 2.65 GeV. Also, the Q² dependence of the Λ(1520) decay angular distribution is presented for the first time. The cosθ_K+ angular distributions suggest t-channel diagrams dominate the production process. Fits to the Λ(1520) t-channel helicity frame decay angular distributions indicate the m …

The Ep → E'P Η Reaction At And Above The S₁₁ (1535) Baryon Resonance, R. Thompson, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, R. A. Niyazov, L. M. Qin, L. B. Weinstein, Et Al., The Clas Collaboration

Physics Faculty Publications

New cross sections for the reaction ep → ep η are reported for total center of mass energy W = 1.5-1.86 GeV and invariant momentum transfer Q² = 0.25-1.5 (GeV/c)². This large kinematic range allows extraction of important new information about response functions, photocouplings, and etaN coupling strengths of baryon resonances. Newly observed structure at W ~ 1.65 GeV is shown to come from interference between S and P waves and can be interpreted with known resonances. Improved values are derived for the photon coupling amplitude for the S₁₁(1535) resonance.

Electrons In Image States Near Roughened Metal Surfaces, Brian K. Clark, Brian W. Gregory, Jean M. Standard

Faculty Publications – Chemistry

Electrons near roughened Ag and Au surfaces with chemisorbed dielectric overlayers of alkanethiol or alkaneselenol self-assembled monolayers are shown to move within the sulfur or selenium head-group layer on the metal terraces. The electrons exist in image states with respect to Ag or Au step edges. There is no substantial image force between the electrons and the terraces.

New Limit On The D Coefficient In Polarized Neutron Decay, L. J. Lising, S. R. Hwang, J. M. Adams, T. J. Bowles, M. C. Browne, T. E. Chupp, K. P. Coulter, M. S. Dewey, S. J. Freedman, B. K. Fujikawa, A. Garcia, G. L. Greene, Gordon L. Jones, H. P. Mumm, J. S. Nico, J. M. Richardson, R. G. H. Robertson, T. D. Steiger, W. A. Teasdale, A. K. Thompson, E. G. Wasserman, F. E. Wietfeldt, R. C. Welsh, J. F. Wilkerson

Articles

We describe an experiment that has set new limits on the time reversal invariance violating D coefficient in neutron beta decay. The emiT experiment measured the angular correlation [J] . (p(e) x p(p)) using an octagonal symmetry that optimizes electron-proton coincidence rates. The result is D=[-0.6+/-1.2(stat)+/-0.5(syst)] x 10(-3). This improves constraints on the phase of g(A)/g(V) and limits contributions to T violation due to leptoquarks. This paper presents details of the experiment, data analysis, and the investigation of systematic effects.

Kinetic Energy Release In Electron-Induced Decay Reactions Of Molecular Ions: C3h8+ And C3h7+, S. Matt, Olof E. Echt, A. Stamatovic, T. D. Mark

Physics & Astronomy

We have measured the kinetic energy release (KER) distributions for electron-induced dissociation of mass-selected molecular parent and fragment ions of propane. They are compared with distributions determined for spontaneous (metastable) dissociation. The average KER for induced dissociation of C3H8+ into C3H7+ is 13.2 +/- 1.2 meV, about 42% larger than for the spontaneous reaction. This large difference is attributed to the dramatically reduced time at which the induced reaction can be sampled. In contrast, the KER for dissociation of C3H7+ into C3H5+, which is characterized by a large reverse activation energy, is hardly affected by the experimental time scale. (C) …

Sans Polarization Analysis With Nuclear-Spin-Polarized He-3, T. R. Gentile, Gordon L. Jones, A. K. Thompson, J. Barker, C. J. Glinka, B. Hammouda, J. W. Lynn

Articles

A neutron spin filter based on transmission through nuclear-spin-polarized He-3 gas has been applied to polarization analysis of small angle neutron scattering (SANS). Such spin filters, which are based on the large spin dependence of the absorption of neutrons by He-3, make SANS polarization analysis possible because of their large angular acceptance. In the present experiment, a He-3-based analyzer was employed to separate nuclear scattering into its coherent and spin-incoherent components. Polarized He-3 analyzers were prepared by two different optical pumping methods and installed on the NG3 SANS instrument at the NIST Center for Neutron Research (NCNR). Measurements were taken …

Low Temperature Anomaly In Mesoscopic Kondo Wires, P. Mohanty, Richard A. Webb

Faculty Publications

We report the observation of an anomalous magnetoresistance in extremely dilute quasi-one-dimensional AuFe wires at low temperatures, along with a hysteretic background at low fields. The Kondo resistivity does not show the unitarity limit down to the lowest temperature, implying uncompensated spin states. We suggest that the anomalous magnetoresistance may be understood as the interference correction from the accumulation of geometric phase in the conduction electron wave function around the localized impurity spin.

Classical Versus Quantum Dynamics For A Driven Relativistic Oscillator, Rainer Grobe, Qichang Su, P J. Peverly, R E. Wagner

Faculty publications – Physics

We compare the time evolution of the quantum-mechanical spatial probability density obtained by solving the time-dependent Dirac equation with its classical counterpart obtained from the relativistic Liouville equation for the phase-space density in a regime in which the dynamics is essentially relativistic. For a resonantly driven one-dimensional harmonic oscillator, the simplest nontrivial model system to perform this comparison, we find that, despite the nonlinearity induced by relativity, the classical ensemble description matches the quantum evolution remarkably well.

Quantum Stochastic Dilation Of Completely Positive Semigroups And Flows., Debashish Goswami Dr.

Doctoral Theses

The central theme of the present thesia is quantum stochastic dilation af semigroupe of completely panitive mapa on operator algebran. It is the sim of all mathemati- cal, or even all scientific theorics, to understand a given class of objects through a tanonical and simpler subclass of it. For example, abstract C"-algebras are studied through their conerete realisation as elgebra of operators, contractions on a Hilbert space by unitaries. Hilbert modules by the factorissble ones, to mention anly a few. In most af these caes, a general object of the relavant class is sociated with a canonical candidate of the …

Disorder-Induced Desynchronization In A 2x2 Circular Josephson Junction Array, Adam S. Landsberg

WM Keck Science Faculty Papers

Analytical results are presented which characterize the behavior of a dc-biased, two-dimensional circular array of overdamped Josephson junctions subject to increasing levels of disorder. It is shown that high levels of disorder can abruptly destroy the synchronous functioning of the array. We identify the transition boundary between synchronized and desynchronized behavior, along with the mechanism responsible for the loss of frequency locking. Comparisons with recent results for arrays with rectangular lattice geometries are described.

Renormalons As Dilation Modes In The Functional Space, A. Babansky, I. Balitsky

Physics Faculty Publications

There are two possible sources of the factorial large-order behavior of a typical perturbative series. First, the number of different Feynman diagrams may be large; second, there may be abnormally large diagrams known as renormalons. It is well known that the large combinatorial number of diagrams is described by instanton-type solutions of the classical equations. We demonstrate that, from the functional-integral viewpoint, the renormalons do not correspond to a particular configuration but manifest themselves as dilatation modes in the functional space.

Deeply Virtual Compton Scattering At Small X, Ian Balitsky, Elena Kuchina

Physics Faculty Publications

We calculate the cross section of deeply virtual Compton scattering at large energies and intermediate momentum transfers.

A Spin Network Primer, Seth Major

Articles

Spin networks, essentially labeled graphs, are “good quantum numbers” for the quantum theory of geometry. These structures encompass a diverse range of techniques which may be used in the quantum mechanics of finite dimensional systems, gauge theory, and knot theory. Though accessible to undergraduates,spin network techniques are buried in more complicated formulations. In this paper a diagrammatic method, simple but rich, is introduced through an association of 2×2" role="presentation" style="display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px 2px 0px 0px; margin: 0px; …

Long-Lived Localized Field Configurations In Small Lattices: Application To Oscillons, M. Gleiser, A. Sornborger

Dartmouth Scholarship

Long-lived localized field configurations such as breathers, oscillons, or more complex objects naturally arise in the context of a wide range of nonlinear models in different numbers of spatial dimensions. We present a numerical method, which we call the adiabatic damping method, designed to study such configurations in small lattices. Using three-dimensional oscillons in φ4 models as an example, we show that the method accurately (to one part in 105 or better) reproduces results obtained with static or dynamically expanding lattices, dramatically cutting down in integration time. We further present results for two-dimensional oscillons, whose lifetimes would be prohibitively …

The Design And Construction Of An Out-Of-Plane Sensitive Electronic Speckle Pattern Interferometer For Non-Destructive Testing Applications, Alexander Burden

Masters

There are many non-destructive testing (NDT) techniques use din industry, which employ acoustic emission, ultrasound, X-rays and thermography. Optical interferometric methodology is being increasingly used in industry. Electronic Speckle Pattern Interferometry (ESPI) is one of the principal optical interferometric techniques used in NDT to measure deformations. Optical surface metrology offers many advantages over conventional methods. These include greater sensitivity, improved lateral and vertical resolution, non-contact and full field measurement. Conventional methods of NDT however continue to be chosen over ESPI. The objective of this thesis is focused on making ESPI more feasible as a NDT technique for use in industry. …

Science And Security Watch: A Threat To The United States From Foreign Graduate Students Training In Physics?, Ibpp Editor

International Bulletin of Political Psychology

This article critiques concerns of some United States (US) security analysts that foreign graduate students in physics who train at universities within the US present security vulnerabilities for the US.

A First Principles Warm Inflation Model That Solves The Cosmological Horizon And Flatness Problems, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos

Dartmouth Scholarship

A quantum field theory warm inflation model is presented that solves the horizon and flatness problems. The model obtains, from the elementary dynamics of particle physics, cosmological scale factor trajectories that begin in a radiation dominated regime, enter an inflationary regime, and then smoothly exit back into a radiation dominated regime, with non-negligible radiation throughout the evolution.