Physics Commons^™

Type-1.5 Superconducting State From An Intrinsic Proximity Effect In Two-Band Superconductors, Egor Babaev, Johan Carlstrom, Martin Speight

Egor Babaev

We show that in multiband superconductors even small interband proximity effect can lead to a qualitative change in the interaction potential between superconducting vortices by producing long-range intervortex attraction. This type of vortex interaction results in unusual response to low magnetic fields leading to phase separation into domains of a two-component Meissner states and vortex droplets.

Wrinkling, Folding, And Snapping Instabilities In Polymer Films, Douglas Peter Holmes

Open Access Dissertations

This work focuses on understanding deformation mechanisms and responsiveness associated with the wrinkling, folding, and snapping of thin polymer films. We demonstrated the use of elastic instabilities in confined regimes, such as the crumpling and snapping of surface attached sheets. We gained fundamental insight into a thin film's ability to localize strain. By taking advantage of geometric strain localization we were able to develop new strategies for responsive surfaces that will have a broad impact on adhesive, optical, and patterning applications. Using the rapid closure of the Venus flytrap's leafets as dictated by the onset of a snap instability as …

A Switch In Retrograde Signaling From Survival To Stress In Rapid Onset Neurodegeneration, Jennifer Ross, Erika L.F Holzbaur, Robert G. Kalb, Karen E. Wallace, Ram Dixit, Goo-Bo Jeong, Eran Perlson

Jennifer Ross

Retrograde axonal transport of cellular signals driven by dynein is vital for neuronal survival. Mouse models with defects in the retrograde transport machinery, including the Loa mouse (point mutation in dynein) and the Tgdynamitin mouse (overexpression of dynamitin), exhibit mild neurodegenerative disease. Transport defects have also been observed in more rapidly progressive neurodegeneration, such as that observed in the SOD1G93A transgenic mouse model for familial amyotrophic lateral sclerosis (ALS). Here, we test the hypothesis that alterations in retrograde signaling lead to neurodegeneration. In vivo, in vitro, and live-cell imaging motility assays show misregulation of transport and inhibition of retrograde signaling …

Non-Isotropy Of The Cmb Power Spectrum In Single Field Inflation, John Donoghue, Koushik Dutta, Andreas Ross

John Donoghue

Contaldi et al. [1] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low multipoles. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low multipoles.

Gauge Federation As An Alternative To Unification, John Donoghue, Preema Pais

John Donoghue

We motivate and explore the possibility that extra SU(N) gauge groups may exist independently of the Standard Model groups, yet not be subgroups of some grand unified group. We study the running of the coupling constants as a potential evidence for a common origin of all the gauge theories. Several different example are displayed. Some of the multiple options involve physics at the TeV scale.

The Conformational Gymnastics Of The Escherichia Coli Seca Molecular Machine And Its Interactions With Signal Sequences, Jenny Lynn Maki

Open Access Dissertations

Protein secretion is a selective and regulated process that is essential in all organisms. In bacteria the preprotein translocase SecA, either free in the cytosol or associated with the SecYEG translocon, recognizes and binds most post-translational secretory proteins containing an N-terminal signal sequence. In Gram-negative bacteria, the molecular chaperone SecB binds many of the preproteins to keep them in a translocation-competent state. Subsequently, SecB delivers the preproteins to the translocon-associated SecA, which binds the signal sequence and also interacts with mature regions of the preprotein. After the preprotein/SecA/SecYEG complex has formed, the energy derived from ATP hydrolysis by SecA coupled …

Transitional Probabilities For The Four-State Random Walk On A Lattice In The Presence Of Partially Reflecting Boundaries, Ramakrishna Janaswamy

Ramakrishna Janaswamy

The four-state random walk (4RW) model, wherein the particle is endowed with two states of spin and two states of directional motion in each space coordinate, permits a stochastic solution of the Schrödinger equation (or the equivalent parabolic equation) without resorting to the usual analytical continuation in complex space of the particle trajectories. Analytical expressions are derived here for the various transitional probabilities in a 4RW by employing generating functions and eigenfunction expansions when the particle moves on a 1+1 space-time lattice with two-point boundary conditions. The most general case of dissimilar boundaries with partially reflecting boundary conditions is treated …

Abc's Of Dew (Adi) Software, John Pickle

STEM Digital

Introduction to three color light, pixels, DEW (ADI) tools

Drag Reduction In Turbulent Flows Over Micropatterned Superhydrophobic Surfaces, Robert J. Daniello

Masters Theses 1911 - February 2014

Periodic, micropatterned superhydrophobic surfaces, previously noted for their ability to provide drag reduction in the laminar flow regime, have been demonstrated capable of reducing drag in the turbulent flow regime as well. Superhydrophobic surfaces contain micro or nanoscale hydrophobic features which can support a shear-free air-water interface between peaks in the surface topology. Particle image velocimetry and pressure drop measurements were used to observe significant slip velocities, shear stress, and pressure drop reductions corresponding to skin friction drag reductions approaching 50%. At a given Reynolds number, drag reduction was found to increase with increasing feature size and spacing, as in …

Nanofilters For Clean Water, Morton Sternheim

Nanotechnology Teacher Summer Institutes

•The problem: adequate clean water •Kinds of filters •Desalination of salt water •Cleaning polluted water •Hands on nanofiltration experiment Adapted from the Nanosense project: http://nanosense.sri.com/activities/finefilters/index.html

More On Powers Of Ten, Morton Sternheim

Nanotechnology Teacher Summer Institutes

A powers of ten personation and activity adapted from the Nanosense project:

http://nanosense.sri.com/activities/sizematters/index.html

Department Of Physics Newsletter: Spring 2009, John Donoghue, Bob Krotkov, Ken Langley, Gerry Peterson, Monroe Rabin, Hajime Sakai

Physics Newsletters

No abstract provided.

Molecular-Dynamics Simulations Of Stacking-Fault-Induced Dislocation Annihilation In Pre-Strained Ultrathin Single-Crystalline Copper Films, Kedarnath Kolluri, M. Rauf Gungor, Dimitrios Maroudas

Physics Department Faculty Publication Series

We report results of large-scale molecular-dynamics (MD) simulations of dynamic deformation under biaxial tensile strain of pre-strained single-crystalline nanometerscale- thick face-centered cubic (fcc) copper films. Our results show that stacking faults, which are abundantly present in fcc metals, may play a significant role in the dissociation, cross-slip, and eventual annihilation of dislocations in small-volume structures of fcc metals. The underlying mechanisms are mediated by interactions within and between extended dislocations that lead to annihilation of Shockley partial dislocations or formation of perfect dislocations. Our findings demonstrate dislocation starvation in small-volume structures with ultra-thin film geometry, governed by a mechanism other …

Nonisotropy In The Cmb Power Spectrum In Single Field Inflation, Jf Donoghue, K Dutta, A Ross

Physics Department Faculty Publication Series

Contaldi et al. [C. R. Contaldi, M. Peloso, L. Kofman, and A. Linde, J. Cosmol. Astropart. Phys. 07 (2003) 002] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low values of ℓ. We investigate the nature of this asymmetry and comment on its …

Remarks On The Minimal Vectorial Standard Model, Mohamed M. Anber, Ufuk Aydemir, John F. Donoghue, Preema Pais

Physics Department Faculty Publication Series

We explore the available parameter space of the minimal vectorial standard model. In this theory, the gauge currents are initially vectorial but the Higgs sector produces chiral mass eigenstates, leading to a set of heavy right-handed mirror particles. We describe the phenomenology of the residual parameter space and suggest that the model will be readily tested at the LHC.

Non-Meissner Electrodynamics And Knotted Solitons In Two-Component Superconductors, Egor Babaev

Physics Department Faculty Publication Series

I consider electrodynamics and the problem of knotted solitons in two-component superconductors. Possible existence of knotted solitons in multicomponent superconductors was predicted several years ago. However, their basic properties and stability in these systems remain an outstandingly difficult question both for analytical and numerical treatment. Here I propose a special perturbative approach to treat self-consistently all the degrees of freedom in the problem. I show that there exists a length scale for a Hopfion texture where the electrodynamics of a two-component superconductor is dominated by a self-induced Faddeev term, which is in stark contrast to the Meissner electrodynamics of single-component …

Magnetic Field Delocalization And Flux Inversion In Fractional Vortices In Two-Component Superconductors, Egor Babaev, Juha Jaykka, Martain Speight

Physics Department Faculty Publication Series

We demonstrate that, in contrast with the single-component Abrikosov vortex, in two-component superconductors vortex solutions with an exponentially screened magnetic field exist only in exceptional cases: in the case of vortices carrying an integer number of flux quanta and in a special parameter limit for half-quantum vortices. For all other parameters, the vortex solutions have a delocalized magnetic field with a slowly decaying tail. Furthermore, we demonstrate a new effect which is generic in two-component systems but has no counterpart in single-component systems: on exactly half of the parameter space of the U(1)×U(1) Ginzburg-Landau model, the magnetic field of a …

Sign-Alternating Interaction Mediated By Strongly Correlated Lattice Bosons, S Söyler, B Capogrosso-Sansone, Nikolai Prokof'ev, Boris Svistunov

Physics Department Faculty Publication Series

We reveal a generic mechanism of generating sign-alternating intersite interactions mediated by strongly correlated lattice bosons. The ground-state phase diagram of the two-component hard-core Bose–Hubbard model on a square lattice at half-integer filling factor for each component, obtained by worm algorithm Monte Carlo simulations, is strongly modified by these interactions and features the solid+superfluid (SF) phase for strong asymmetry between the hopping amplitudes. The new phase is a direct consequence of the effective nearest-neighbor repulsion between 'heavy' atoms mediated by the 'light' SF component. Due to their sign-alternating character, mediated interactions lead to a rich variety of yet to be …

Extrinsic Curvature, Geometric Optics, And Lamellar Order On Curved Substrates, R Kamien, D Nelson, Christian Santangelo, V Vitelli

Physics Department Faculty Publication Series

When thermal energies are weak, two-dimensional lamellar structures confined on a curved substrate display complex patterns arising from the competition between layer bending and compression in the presence of geometric constraints. We present broad design principles to engineer the geometry of the underlying substrate so that a desired lamellar pattern can be obtained by self-assembly. Two distinct physical effects are identified as key factors that contribute to the interaction between the shape of the underlying surface and the resulting lamellar morphology. The first is a local ordering field for the direction of each individual layer, which tends to minimize its …

Enthalpy And The Mechanics Of Ads Black Holes, David Kastor, Sourya Ray, Jennie Traschen

Physics Department Faculty Publication Series

We present geometric derivations of the Smarr formula for static AdS black holes and an expanded first law that includes variations in the cosmological constant. These two results are further related by a scaling argument based on Euler's theorem. The key new ingredient in the constructions is a two-form potential for the static Killing field. Surface integrals of the Killing potential determine the coefficient of the variation of Λ in the first law. This coefficient is proportional to a finite, effective volume for the region outside the AdS black hole horizon, which can also be interpreted as minus the volume …

A Percolation-Theoretic Approach To Spin Glass Phase Transitions, Jonathan Machta, C. M. Newman, D. L. Stein

Jonathan Machta

The magnetically ordered, low temperature phase of Ising ferromagnets is manifested within the associated Fortuin—Kasteleyn (FK) random cluster representation by the occurrence of a single positive density percolating cluster. In this paper, we review our recent work on the percolation signature for Ising spin glass ordering — both in the short-range Edwards—Anderson (EA) and infinite-range Sherrington—Kirkpatrick (SK) models — within a tworeplica FK representation and also in the different Chayes—Machta—Redner two-replica graphical representation. Numerical studies of the ±J EA model in dimension three and rigorous results for the SK model are consistent in supporting the conclusion that the signature of …

Strengths And Weaknesses Of Parallel Tempering, Jonathan Machta

Jonathan Machta

Parallel tempering, also known as replica exchange Monte Carlo, is studied in the context of two simple free-energy landscapes. The first is a double-well potential defined by two macrostates separated by a barrier. The second is a “golf course” potential defined by microstates having two possible energies with exponentially more high-energy states than low-energy states. The equilibration time for replica exchange is analyzed for both systems. For the double-well system, parallel tempering with a number of replicas that scales as the square root of the barrier height yields exponential speedup of the equilibration time. On the other hand, replica exchange …

Comments On The Minimal Vectorial Standard Model, Mohamed M. Anber, Ufuk Aydemir, John Donoghue, Preema Pais

John Donoghue

We explore the available parameter space of the minimal vectorial Standard Model. In this theory, the gauge currents are initially vectorial but the Higgs sector produces chiral mass eigenstates, leading to a set of heavy right-handed mirror particles. We describe the phenomenology of the residual parameter space and suggest that the model will be readily tested at the LHC.

Phase Diagram Of The Disordered Bose-Hubbard Model, V Gurarie, L Pollet, Nikolai Prokof'ev, Boris Svistunov, M Troyer

Physics Department Faculty Publication Series

We establish the phase diagram of the disordered three-dimensional Bose-Hubbard model at unity filling which has been controversial for many years. The theorem of inclusions, proven by Pollet et al. [Phys. Rev. Lett. 103, 140402 (2009)] states that the Bose-glass phase always intervenes between the Mott insulating and superfluid phases. Here, we note that assumptions on which the theorem is based exclude phase transitions between gapped (Mott insulator) and gapless phases (Bose glass). The apparent paradox is resolved through a unique mechanism: such transitions have to be of the Griffiths type when the vanishing of the gap at the critical …

Comments On The Minimal Vectorial Standard Model, Mohamed M. Anber, Ufuk Aydemir, John Donoghue, Preema Pais

Physics Department Faculty Publication Series

We explore the available parameter space of the minimal vectorial Standard Model. In this theory, the gauge currents are initially vectorial but the Higgs sector produces chiral mass eigenstates, leading to a set of heavy right-handed mirror particles. We describe the phenomenology of the residual parameter space and suggest that the model will be readily tested at the LHC.

Unconventional Rotational Responses Of Hadronic Superfluids In A Neutron Star Caused By Strong Entrainment And A Σ- Hyperon Gap, Egor Babaev

Physics Department Faculty Publication Series

I show that the usual model of the rotational response of a neutron star, which predicts rotation-induced neutronic vortices and no rotation-induced protonic vortices, does not hold (i) beyond a certain threshold of entrainment interaction strength nor (ii) in the case of nonzero Σ- hyperon gap. I show that in both of these cases the rotational response involves the creation of phase windings in an electrically charged condensate. Lattices of bound states of vortices which result from these phase windings can (for a range of parameters) strongly reduce the interaction between rotation-induced vortices with magnetic-field carrying superconducting components.

Period Fissioning And Other Instabilities Of Stressed Elastic Membranes, B Davidovitch

Physics Department Faculty Publication Series

We study the shapes of elastic membranes under the simultaneous exertion of tensile and compressive forces when the translational symmetry along the tension direction is broken. We predict a multitude of morphological phases in various regimes of a two-dimensional parameter space (ϵ,ν) that defines the relevant mechanical and geometrical conditions. These parameters are, respectively, the ratio between compression and tension, and the wavelength contrast along the tension direction. The predicted patterns emerge through new transition and instability mechanisms and include several types of irregular and smooth cascades composed of wrinkles and sharp folds. In particular, the hierarchical morphology predicted under …

Absence Of A Direct Superfluid To Mott Insulator Transition In Disordered Bose Systems, L Pollet, N Prokof'ev, B Svistunov, Troyer

Physics Department Faculty Publication Series

We prove the absence of a direct quantum phase transition between a superfluid and a Mott insulator in a bosonic system with generic, bounded disorder. We also prove the compressibility of the system on the superfluid–insulator critical line and in its neighborhood. These conclusions follow from a general theorem of inclusions, which states that for any transition in a disordered system, one can always find rare regions of the competing phase on either side of the transition line. Quantum Monte Carlo simulations for the disordered Bose-Hubbard model show an even stronger result, important for the nature of the Mott insulator …

Superfluid Transition In A Bose Gas With Correlated Disorder, S Pilati, S Giorgini, Nikolai Prokof'ev

Physics Department Faculty Publication Series

The superfluid transition of a three-dimensional gas of hard-sphere bosons in a disordered medium is studied using quantum Monte Carlo methods. Simulations are performed in continuous space both in the canonical and in the grand-canonical ensemble. At fixed density we calculate the shift of the transition temperature as a function of the disorder strength, while at fixed temperature we determine both the critical chemical potential and the critical density separating normal and superfluid phases. In the regime of strong disorder the normal phase extends up to large values of the degeneracy parameter, and the critical chemical potential exhibits a linear …

Underlying Mechanism For The Giant Isochoric Compressibility Of Solid 4he: Superclimb Of Dislocations, S Söyler, A Kuklov, L Pollet, Nikolai Prokof'ev, Boris Svistunov

Physics Department Faculty Publication Series

In the experiment on superfluid transport in solid 4He [Phys. Rev. Lett. 100, 235301 (2008)], Ray and Hallock observed an anomalously large isochoric compressibility: the supersolid samples demonstrated a significant and apparently spatially uniform response of density and pressure to chemical potential, applied locally through Vycor “electrodes.” We propose that the effect is due to superclimb: edge dislocations can climb because of mass transport along superfluid cores. We corroborate the scenario by ab initio simulations of an edge dislocation in solid 4He at T=0.5  K. We argue that at low temperature the effect must be suppressed due to a crossover …