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Articles 1 - 27 of 27
Full-Text Articles in Physics
Constraints On The Variability Of Quark Masses From Nuclear Binding, Thibault Damour, John Donoghue
Constraints On The Variability Of Quark Masses From Nuclear Binding, Thibault Damour, John Donoghue
John Donoghue
Based on recent work on nuclear binding, we update and extend the anthropic constraints on the light quark masses, with results that are more tightly constrained than previously obtained. We find that heavy nuclei would fall apart (because the attractive nuclear central potential becomes too weak) if the sum of the light quark masses m_u+m_d would exceed their physical values by 64% (at 95% confidence level). We summarize the anthropic constraints that follow from requiring the existence both of heavy atoms and of hydrogen. With the additional assumption that the quark Yukawa couplings do not vary, these constraints provide a …
Complementary Dimerization Of Microtubule-Associated Protein Tau: Implications For Microtubule Bundling And Tau-Mediated Pathogensis, Jennifer Ross, Kenneth J. Rosenberg, H. Eric Feinstein, Stuart C. Feinstein, Jacob Israelachvili
Complementary Dimerization Of Microtubule-Associated Protein Tau: Implications For Microtubule Bundling And Tau-Mediated Pathogensis, Jennifer Ross, Kenneth J. Rosenberg, H. Eric Feinstein, Stuart C. Feinstein, Jacob Israelachvili
Jennifer Ross
Tau is an intrinsically unstructured microtubule (MT)-associated protein capable of binding to and organizing MTs into evenly spaced parallel assemblies known as “MT bundles.” How tau achieves MT bundling is enigmatic because each tau molecule possesses only one MT-binding region. To dissect this complex behavior, we have used a surface forces apparatus to measure the interaction forces of the six CNS tau isoforms when bound to mica substrates in vitro. Two types of measurements were performed for each isoform: symmetric configuration experiments measured the interactions between two tau-coated mica surfaces, whereas “asymmetric” experiments examined tau-coated surfaces interacting with a smooth …
A Scintillator Purification System For The Borexino Solar Neutrino Detector, Andrea Pocar
A Scintillator Purification System For The Borexino Solar Neutrino Detector, Andrea Pocar
Andrea Pocar
Purification of the 278 tons of liquid scintillator and 889 tons of buffer shielding for the Borexino solar neutrino detector was performed with a system that combined distillation, water extraction, gas stripping and filtration. The purification of the scintillator achieved unprecedented low backgrounds for the large scale liquid scintillation detector. This paper describes the principles of operation, design, construction and commissioning of the purification system, and reviews the requirements and methods to achieve system cleanliness and leak-tightness.
Department Of Physics Newsletter: Spring 2008, Bob Krotkov, Ken Langley, Gerry Peterson, Monroe Rabin, Hajime Sakai
Department Of Physics Newsletter: Spring 2008, Bob Krotkov, Ken Langley, Gerry Peterson, Monroe Rabin, Hajime Sakai
Physics Newsletters
No abstract provided.
Quantum-Limited Mass Flow Of Liquid He-3, G Lambert, G Gervais, Wj Mullin
Quantum-Limited Mass Flow Of Liquid He-3, G Lambert, G Gervais, Wj Mullin
Physics Department Faculty Publication Series
We consider theoretically the possibility of observing unusual quantum fluid behavior in liquid 3He and solutions of 3He in 4He systems confined to nanochannels. In the case of pure ballistic flow at very low temperature the conductance will be quantized in units of 2m2/h. We show that these steps should be sensitive to increases in temperature. We also use a random scattering matrix simulation to study flow with diffusive wall scattering. Universal conductance fluctuations analogous to those seen in electron systems should then be observable. Finally we consider the possibility of crossover to a one-dimensional system at sufficiently low temperature, …
Hidden Vortex Lattices In A Thermally Paired Superfluid, E. K. Dahl, E. Babaev, A. Sudbø
Hidden Vortex Lattices In A Thermally Paired Superfluid, E. K. Dahl, E. Babaev, A. Sudbø
Physics Department Faculty Publication Series
We study the evolution of rotational response of a statistical mechanical model of two-component superfluid with a nondissipative drag interaction as the system undergoes a transition into a paired superfluid phase at finite temperature. The transition manifests itself in a change of (i) vortex-lattice symmetry and (ii) nature of the vortex state. Instead of a vortex lattice, the system forms a highly disordered tangle which constantly undergoes merger and reconnecting processes involving different types of vortices with a “hidden” breakdown of translation symmetry.
Effects Of Boundaries And Density Inhomogeneity On States Of Vortex Matter In Bose-Einstein Condensates At Finite Temperature, S. Kragset, E. Babaev, A. Sudbø Sudbø
Effects Of Boundaries And Density Inhomogeneity On States Of Vortex Matter In Bose-Einstein Condensates At Finite Temperature, S. Kragset, E. Babaev, A. Sudbø Sudbø
Physics Department Faculty Publication Series
Most of the literature on quantum vortices predicting various states of vortex matter in three dimensions at finite temperatures in quantum fluids is based on the assumption of an extended and homogeneous system. This is well known not to be the case in actual Bose-Einstein condensates in traps, which are finite systems with nonuniform density. This raises the question to what extent one can speak of different aggregate states of vortex matter (vortex lattices, liquids, and tensionless vortex tangles) in these systems. To address this point, in the present work we focus on the finite-size, boundaries and density inhomogeneity effects …
Bold Diagrammatic Monte Carlo: A Generic Sign-Problem Tolerant Technique For Polaron Models And Possibly Interacting Many-Body Problems, N Prokof'ev, B Svistunov
Bold Diagrammatic Monte Carlo: A Generic Sign-Problem Tolerant Technique For Polaron Models And Possibly Interacting Many-Body Problems, N Prokof'ev, B Svistunov
Physics Department Faculty Publication Series
We develop a Monte Carlo scheme for sampling series of Feynman diagrams for the proper self-energy, which are self-consistently expressed in terms of renormalized particle propagators. This approach is used to solve the problem of a single spin-down fermion resonantly interacting with the Fermi gas of spin-up particles. Though the original series based on bare propagators are sign alternating and divergent, one can still determine the answer behind them by using two strategies (separately or together): (i) using proper series resummation techniques and (ii) introducing renormalized propagators which are defined in terms of the simulated proper self-energy, i.e., making the …
Search For Deconfined Criticality: Su(2) D´Ej`A Vu, B Kuklov, M Matsumoto, Nikolai Prokof'ev, Boris Svistunov, M Troyer
Search For Deconfined Criticality: Su(2) D´Ej`A Vu, B Kuklov, M Matsumoto, Nikolai Prokof'ev, Boris Svistunov, M Troyer
Physics Department Faculty Publication Series
Monte Carlo simulations of the SU(2)-symmetric deconfined critical point action reveal strong violations of scale invariance for the deconfinement transition. We find compelling evidence that the generic runaway renormalization flow of the gauge coupling is to a weak first order transition, similar to the case of U(1)×U(1) symmetry. Our results imply that recent numeric studies of the N`eel antiferromagnet to valence bond solid quantum phase transition in SU(2)-symmetric models were not accurate enough in determining the nature of the transition.
Local Stress And Superfluid Properties Of Solid 4he, L Pollet, M Boninsegni, A Kuklov, Nikolai Prokof'ev, Boris Svistunov, M Troyer
Local Stress And Superfluid Properties Of Solid 4he, L Pollet, M Boninsegni, A Kuklov, Nikolai Prokof'ev, Boris Svistunov, M Troyer
Physics Department Faculty Publication Series
We provide a semiquantitative tool, derived from first-principles simulations, for answering the question of whether certain types of defects in solid 4He support mass superflow. Although ideal crystals of 4He are not supersolid, the gap for vacancy creation closes when applying a moderate stress. While a homogeneous system becomes unstable at this point, the stressed core of crystalline defects (dislocations and grain boundaries) can turn superfluid.
Kolmogorov And Kelvin-Wave Cascades Of Superfluid Turbulence At T=0: What Lies Between, E Kozik, Boris Svistunov
Kolmogorov And Kelvin-Wave Cascades Of Superfluid Turbulence At T=0: What Lies Between, E Kozik, Boris Svistunov
Physics Department Faculty Publication Series
As long as vorticity quantization remains irrelevant for long-wave physics, superfluid turbulence supports a regime macroscopically identical to the Kolmogorov cascade of a normal liquid. At high enough wave numbers, the energy flux in wavelength space is carried by individual Kelvin-wave cascades on separate vortex lines. We analyze the transformation of the Kolmogorov cascade into the Kelvin-wave cascade, revealing a chain of three distinct intermediate cascades supported by local-induction motion of the vortex lines and distinguished by specific reconnection mechanisms. The most prominent qualitative feature predicted is unavoidable production of vortex rings of a characteristic size.
Scanning Superfluid-Turbulence Cascade By Its Low-Temperature Cutoff, E Kozik, Boris Svistunov
Scanning Superfluid-Turbulence Cascade By Its Low-Temperature Cutoff, E Kozik, Boris Svistunov
Physics Department Faculty Publication Series
On the basis of a recently proposed scenario of the transformation of the Kolmogorov cascade into the Kelvin-wave cascade, we develop a theory of low-temperature cutoff. The theory predicts a specific behavior of the quantized vortex line density, L, controlled by the frictional coefficient, α(T)≪1, responsible for the cutoff. The curve ln L(lnα) is found to directly reflect the structure of the cascade, revealing four qualitatively distinct wave number regions. Excellent agreement with a recent experiment by Walmsley et al. [Phys. Rev. Lett. 99, 265302 (2007)]—in which L(T) has been measured down to T∼0.08 K—implies that the scenario of low-temperature …
Komar Integrals In Higher (And Lower) Derivative Gravity, David Kastor
Komar Integrals In Higher (And Lower) Derivative Gravity, David Kastor
Physics Department Faculty Publication Series
This is the pre-published version harvested from ArXiv. The published version is located at http://iopscience.iop.org/0264-9381/25/17/175007/
Epr Argument And Bell Inequalities For Bose-Einstein Spin Condensates, Franck Laloe, Wj Mullin
Epr Argument And Bell Inequalities For Bose-Einstein Spin Condensates, Franck Laloe, Wj Mullin
Physics Department Faculty Publication Series
We discuss the properties of two Bose-Einstein condensates in different spin states, represented quantum mechanically by a double Fock state. Individual measurements of the spins of the particles are performed in transverse directions (perpendicular to the spin quantization axis), giving access to the relative phase of the two macroscopically occupied states. Before the first spin measurement, the phase is completely undetermined; after a few measurements, a more and more precise knowledge of its value emerges under the effect of the quantum measurement process. This naturally leads to the usual notion of a quasiclassical phase (Anderson phase) and to an interesting …
Superfluids, Superconductors And Supersolids: Macroscopic Manifestations Of The Microworld Laws, Egor Babaev
Superfluids, Superconductors And Supersolids: Macroscopic Manifestations Of The Microworld Laws, Egor Babaev
Egor Babaev
A superconductor is a state of matter in which electrons flow without. Resistance. A superfluid is a fluid devoid of viscosity. Superfluidity was first. Discovered in experiments on helium conducted by Petr Kapitsa in 1937.. The lack of viscosity is a phenomenon which is highly counterintuitive. From the point of view of the classical physics on which our intuition is. Based. This phenomenon has a quantum nature, i.e. it is related to the. Physics of the microworld, where particles are divided into two classes:. Bosons and fermions. One of the fundaAssistant Professor Egor Babaev. Number of particles ‘conspire’ to behave.
Multibody Interactions In Coarse-Graining Schemes For Extended Systems, S Are, Ma Katsoulakis, P Plechac, L Rey-Bellet
Multibody Interactions In Coarse-Graining Schemes For Extended Systems, S Are, Ma Katsoulakis, P Plechac, L Rey-Bellet
Luc Rey-Bellet
In this paper we address the role of multibody interactions for the coarse-grained approximation of stochastic lattice systems. Such interaction potentials are often not included in coarse-graining schemes, as they can be computationally expensive. The multibody interactions are obtained from the error expansion of the reference measure which is, in many cases, chosen as a Gibbs measure corresponding to a local mean-field approximation. We identify the parameter $\epsilon$ that characterizes the level of approximation and its relation to the underlying interaction potential. The error analysis suggests strategies to overcome the computational costs due to evaluations of multibody interactions by additional …
The Percolation Signature Of The Spin Glass Transition, Jonathan Machta, C. M. Newman, D. L. Stein
The Percolation Signature Of The Spin Glass Transition, Jonathan Machta, C. M. Newman, D. L. Stein
Jonathan Machta
Magnetic ordering at low temperature for Ising ferromagnets manifests itself within the associated Fortuin–Kasteleyn (FK) random cluster representation as the occurrence of a single positive density percolating network. In this paper we investigate the percolation signature for Ising spin glass ordering—both in short-range (EA) and infinite-range (SK) models—within a two-replica FK representation and also within the different Chayes–Machta–Redner two-replica graphical representation. Based on numerical studies of the ±J EA model in three dimensions and on rigorous results for the SK model, we conclude that the spin glass transition corresponds to the appearance of two percolating clusters of unequal densities.
High-Resolution Saturation Spectroscopy Of Singly-Ionized Iron With A Pulsed Uv Laser, M. Ascoli, E. E. Eyler, David Kawall, David Demille
High-Resolution Saturation Spectroscopy Of Singly-Ionized Iron With A Pulsed Uv Laser, M. Ascoli, E. E. Eyler, David Kawall, David Demille
David Kawall
We describe the design and realization of a scheme for UV laser spectroscopy of singly-ionized iron (Fe II) with very high resolution. A buffer-gas cooled laser ablation source is used to provide a room-temperature plasma with a high density of Fe II. We combine this with a scheme for pulsed-laser saturation spectroscopy to yield sub-Doppler resolution. In a demonstration experiment, we have examined an Fe II transition near 260 nm, attaining a linewidth of about 250 MHz. The method is well suited to measure transition frequencies and hyperfine structure. It could also be used to measure small isotope shifts in …
Percolation In The Sherrington-Kirkpatrick Spin Glass, Jonathan Machta, C. M. Newman, D. L. Stein
Percolation In The Sherrington-Kirkpatrick Spin Glass, Jonathan Machta, C. M. Newman, D. L. Stein
Jonathan Machta
We present extended versions and give detailed proofs of results about percolation (using various sets of two-replica bond occupation variables) in Sherrington-Kirkpatrick spin glasses (with zero external field) that were first given in an earlier paper by the same authors. We also explain how ultrametricity is manifested by the densities of large percolating clusters. Our main theorems concern the connection between these densities and the usual spin overlap distribution. Their corollaries are that the ordered spin glass phase is characterized by a unique percolating cluster of maximal density (normally coexisting with a second cluster of nonzero but lower density). The …
Diffusion And Binding Of Finite-Size Particles In Confined Geometries, M Henle, B Didonna, Christian Santangelo, A Gopinathan
Diffusion And Binding Of Finite-Size Particles In Confined Geometries, M Henle, B Didonna, Christian Santangelo, A Gopinathan
Physics Department Faculty Publication Series
Describing the diffusion of particles through crowded, confined environments with which they can interact is of considerable biological and technological interest. Under conditions where the confinement dimensions become comparable to the particle dimensions, steric interactions between particles, as well as particle-wall interactions, will play a crucial role in determining transport properties. To elucidate the effects of these interactions on particle transport, we consider the diffusion and binding of finite-size particles within a channel whose diameter is comparable to the size of the particles. Using a simple lattice model of this process, we calculate the steady-state current and density profiles of …
The Thermodynamics Of Kaluza–Klein Black Hole/Bubble Chains, David Kastor, Sourya Ray, Jennie Traschen
The Thermodynamics Of Kaluza–Klein Black Hole/Bubble Chains, David Kastor, Sourya Ray, Jennie Traschen
Physics Department Faculty Publication Series
A Killing bubble is a minimal surface that arises as the fixed surface of a spacelike Killing field. We compute the bubble contributions to the Smarr relations and the mass and tension first laws for spacetimes containing both black holes and Killing bubbles. The resulting relations display an interesting interchange symmetry between the properties of black hole horizons and those of KK bubbles. This interchange symmetry reflects the underlying relation between static bubbles and black holes under double analytic continuation of the time and Kaluza–Klein directions. The thermodynamics of bubbles involve a geometrical quantity that we call the bubble surface …
Unusual States Of Vortex Matter In Mixtures Of Bose-Einstein Condensates On Rotating Optical Lattices, E. K. Dahl, E. Babaev, A. Sudbø
Unusual States Of Vortex Matter In Mixtures Of Bose-Einstein Condensates On Rotating Optical Lattices, E. K. Dahl, E. Babaev, A. Sudbø
Physics Department Faculty Publication Series
In a single-component superfluid under rotation a broken symmetry in the order parameter space results in a broken translational symmetry in real space: a vortex lattice. If translational symmetry is restored, the phase of the order parameter disorders and thus the broken symmetry in the order parameter space is also restored. We show that for Bose-Einstein condensate mixtures in optical lattices with negative dissipationless drag, a new situation arises. This state is a modulated vortex liquid which breaks translational symmetry in the direction transverse to the rotation vector.
Observation Of Unusual Mass Transport In Solid Hcp 4he, M Ray, R Hallock
Observation Of Unusual Mass Transport In Solid Hcp 4he, M Ray, R Hallock
Physics Department Faculty Publication Series
Solid 4He has been created off the melting curve by growth at a nearly constant mass via the “blocked capillary” technique and growth from the 4He superfluid at constant temperature. The experimental apparatus allows injection of 4He atoms from superfluid directly into the solid. Evidence for the superfluidlike transport of mass through a sample cell filled with hcp solid 4He off the melting curve is found. This mass flux depends on temperature and pressure.
Asymptotic Behavior Of The Magnetization Near Critical And Tricritical Points Via Ginzburg–Landau Polynomials, R Ellis, J Machta, P Otto
Asymptotic Behavior Of The Magnetization Near Critical And Tricritical Points Via Ginzburg–Landau Polynomials, R Ellis, J Machta, P Otto
Physics Department Faculty Publication Series
The purpose of this paper is to prove connections among the asymptotic behavior of the magnetization, the structure of the phase transitions, and a class of polynomials that we call the Ginzburg–Landau polynomials. The model under study is a mean-field version of a lattice spin model due to Blume and Capel. It is defined by a probability distribution that depends on the parameters β and K, which represent, respectively, the inverse temperature and the interaction strength. Our main focus is on the asymptotic behavior of the magnetization m(β n ,K n ) for appropriate sequences (β n ,K n ) …
Fermi-Polaron Problem: Diagrammatic Monte Carlo Method For Divergent Sign-Alternating Series, Nikolai Prokof'ev, Boris Svistunov
Fermi-Polaron Problem: Diagrammatic Monte Carlo Method For Divergent Sign-Alternating Series, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
We use the diagrammatic Monte Carlo approach to solve the problem of a single spin-down fermion resonantly interacting with a Fermi gas of spin-up particles. Our solution is important for understanding the phase diagram and properties of the crossover from the BCS regime to the Bose-Einstein condensate in the strongly imbalanced regime. On the technical side, we develop a generic sign-problem-tolerant method for exact numerical solution of polaron-type models. This is a characteristic example of how Monte Carlo methods can be used to simulate divergent sign-alternating diagrammatic series.
Interference Of Bose-Einstein Condensates: Quantum Nonlocal Effects, Wj Mullin, F Laloe
Interference Of Bose-Einstein Condensates: Quantum Nonlocal Effects, Wj Mullin, F Laloe
Physics Department Faculty Publication Series
Quantum systems in Fock states do not have a phase. When two or more Bose-Einstein condensates are sent into interferometers, they nevertheless acquire a relative phase under the effect of quantum measurements. The usual explanation relies on spontaneous symmetry breaking, where phases are ascribed to all condensates and treated as unknown classical quantities. However, this image is not always sufficient: when all particles are measured, quantum mechanics predicts probabilities that are sometimes in contradiction with it, as illustrated by quantum violations of local realism. In this Rapid communication, we show that interferometers can be used to demonstrate a large variety …
Chiral Corrections To The Vector And Axial Couplings Of Quarks And Baryons, A Faessler, T Gutsche, Br Holstein, Ve Lyubovitskij
Chiral Corrections To The Vector And Axial Couplings Of Quarks And Baryons, A Faessler, T Gutsche, Br Holstein, Ve Lyubovitskij
Physics Department Faculty Publication Series
We calculate chiral corrections to the semileptonic vector and axial quark coupling constants using a manifestly Lorentz covariant chiral quark approach up to order O(p4) in the two- and three-flavor pictures. These couplings are then used in the evaluation of the corresponding couplings which govern the semileptonic transitions between octet baryon states. In the calculation of baryon matrix elements we use a general ansatz for the spatial form of the quark wave function, without referring to a specific realization of hadronization and confinement of quarks in baryons. Matching the physical amplitudes calculated within our approach to the model-independent predictions of …