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Full-Text Articles in Physical Sciences and Mathematics
Molecular-Dynamics Simulations Of Stacking-Fault-Induced Dislocation Annihilation In Pre-Strained Ultrathin Single-Crystalline Copper Films, Kedarnath Kolluri, M. Rauf Gungor, Dimitrios Maroudas
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
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 …
Gauge Federation As An Alternative To Unification, Jf Donoghue, P Pais
Gauge Federation As An Alternative To Unification, Jf Donoghue, P Pais
Physics Department Faculty Publication Series
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.
Remarks On The Minimal Vectorial Standard Model, Mohamed M. Anber, Ufuk Aydemir, John F. Donoghue, Preema Pais
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
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
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 …
Collective Dynamics Of Interacting Ising Spins: Exact Results For The Bethe Lattice, A Burin, N Prokof'ev, I Tupitsyn
Collective Dynamics Of Interacting Ising Spins: Exact Results For The Bethe Lattice, A Burin, N Prokof'ev, I Tupitsyn
Physics Department Faculty Publication Series
We study the low temperature dynamics in films made of molecular magnets, i. e. crystals composed of molecules having large electronic spin S in their ground state. The electronic spin dynamics is mediated by coupling to a nuclear spin bath; this coupling allows transitions for a small fraction of electronic spins between their two energy minima, Sz = ±S, under resonant conditions when the change of the Zeeman energy in magnetic dipolar field of other electronic spins is compensated by interaction with nuclear spins. Transitions of resonant spins can result in opening or closing resonances in their neighbors leading to …
Sign-Alternating Interaction Mediated By Strongly Correlated Lattice Bosons, S Söyler, B Capogrosso-Sansone, Nikolai Prokof'ev, Boris Svistunov
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
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
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 …
When Effective Field Theories Fail, John Donoghue
When Effective Field Theories Fail, John Donoghue
Physics Department Faculty Publication Series
In this talk, I describe and defend four non-standard claims about four effective field theories, and try to extract some lessons about the limits of effective field theory. The four theses (and a capsule diagnosis given in parentheses) are: 1) Kaon loops are not a reliable part of chiral perturbation theory (dimensional regularization does not know about the chiral scale), 2) Regge physics is inappropriately missing from SCET (an infinite set of scales are needed) 3) There is likely a barrier in the use of EFT in general relativity in the extreme infrared (curvature effects build up) and 4) Gauge …
Phase Diagram Of The Disordered Bose-Hubbard Model, V Gurarie, L Pollet, Nikolai Prokof'ev, Boris Svistunov, M Troyer
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
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.
Relating D-0-D-0 Mixing And D-0 -> L(+)L(-) With New Physics, E Golowich, J Hewett, S Pakvasa, Aa Petrov
Relating D-0-D-0 Mixing And D-0 -> L(+)L(-) With New Physics, E Golowich, J Hewett, S Pakvasa, Aa Petrov
Physics Department Faculty Publication Series
We point out how, in certain models of new physics, the same combination of couplings occurs in the amplitudes for both D0-D̅ 0 mixing and the rare decays D0→ℓ+ℓ-. If the new physics dominates and is responsible for the observed mixing, then a very simple correlation exists between the magnitudes of each; in fact the rates for the decay D0→ℓ+ℓ- are completely fixed by the mixing. Observation of D0→ℓ+ℓ- in excess of the standard model prediction could identify new physics contributions to D0-D̅ 0 mixing.
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.
Observation Of Mass Transport Through Solid 4he, M Ray, R Hallock
Observation Of Mass Transport Through Solid 4he, M Ray, R Hallock
Physics Department Faculty Publication Series
By use of an experimental design that provides for superfluid helium in contact with bulk hcp 4He off the melting curve, we have observed the dc transport of mass through a cell filled with solid 4He in the hcp region of the phase diagram. Flow, which shows characteristics of a superflow, is seen to be independent of the method used to grow the solid but depends on pressure and temperature. The temperature dependence suggests the possibility of hysteresis.
Period Fissioning And Other Instabilities Of Stressed Elastic Membranes, B Davidovitch
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
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
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
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 …
Mesophases Of Soft-Sphere Aggregates, H Shin, G Grason, Christian Santangelo
Mesophases Of Soft-Sphere Aggregates, H Shin, G Grason, Christian Santangelo
Physics Department Faculty Publication Series
Soft spheres interacting via a hard core and a range of attractive and repulsive ‘soft-shoulder’ potentials self-assemble into clusters forming a variety of mesophases. We combine a mean-field theory developed from a lattice model with a level surface analysis of the periodic structures of soft-sphere aggregates to study stable morphologies for all clustering potentials. We develop a systematic approach to the thermodynamics of mesophase assembly in the low-temperature, strong-segregation and predict a generic sequence of phases including lamella, hexagonal-columnar and body-center cubic phases, as well as the associated inverse structures. We discuss the finite temperature corrections to strong segregation theory …
Interferometry With Independent Bose-Einstein Condensates: Parity As An Epr/Bell Quantum Variable, F Laloe, Wj Mullin
Interferometry With Independent Bose-Einstein Condensates: Parity As An Epr/Bell Quantum Variable, F Laloe, Wj Mullin
Physics Department Faculty Publication Series
When independent Bose-Einstein condensates (BEC), described quantum mechanically by Fock (number) states, are sent into interferometers, the measurement of the output port at which the particles are detected provides a binary measurement, with two possible results ±1. With two interferometers and two BEC’s, the parity (product of all results obtained at each interferometer) has all the features of an Einstein-Podolsky-Rosen quantity, with perfect correlations predicted by quantum mechanics when the settings (phase shifts of the interferometers) are the same. When they are different, significant violations of Bell inequalities are obtained. These violations do not tend to zero when the number …
Fundamental Neutron Physics: Introduction And Overview Preface, Barry R. Holstein
Fundamental Neutron Physics: Introduction And Overview Preface, Barry R. Holstein
Physics Department Faculty Publication Series
In the 77 years since its discovery by Chadwick in 1932, the neutron has come to play an increasingly important role in contemporary physics. As the next to lightest baryon, it is, of course, one of the two primary components of the atomic nucleus and studies of isotopes (nuclei with varying numbers of neutrons but the same proton number) and of the neutron drip line are one of the important focuses of the recently approved radioactive beam machine to be built at Michigan State University. Precise knowledge of its ~900 second lifetime is crucial to determination of the time at …