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Full-Text Articles in Physical Sciences and Mathematics
Low Background Techniques For The Borexino Nylon Vessels, Andrea Pocar
Low Background Techniques For The Borexino Nylon Vessels, Andrea Pocar
Andrea Pocar
Borexino is an organic liquid scintillator underground detector for low energy solar neutrinos. The experiment has to satisfy extremely stringent low background requirements. The thin nylon spherical scintillator containment vessel has to meet cleanliness and low radioactivity levels second only, within the detector, to the scintillator itself. Overall, the background from the vessel in the fiducial volume of the detector must be kept at the level of one event per day or better. The requirements, design choices, results from laboratory tests, and fabrication techniques that have been adopted to meet this goal are presented. Details of the precautions taken during …
Field-And Temperature-Induced Topological Phase Transitions In Three Dimensional N-Component London Superconductor, J. Smiseth, E. Smorgrav, Egor Babaev, A. Sudbo
Field-And Temperature-Induced Topological Phase Transitions In Three Dimensional N-Component London Superconductor, J. Smiseth, E. Smorgrav, Egor Babaev, A. Sudbo
Egor Babaev
The phase diagram and critical properties of the $N$-component London superconductor are studied both analytically and through large-scale Monte-Carlo simulations in $d=2+1$ dimensions (components here refer to different replicas of the complex scalar field). Examples are given of physical systems to which this model is applicable. The model with different bare phase stiffnesses for each component, is a model of superconductivity which should arise out of metallic phases of light atoms under extreme pressure. A projected mixture of electronic and protonic condensates in liquid metallic hydrogen under extreme pressure is the simplest example, corresponding to N=2. These are such that …
Classical Physics And Quantum Loops, Barry R. Holstein, John Donoghue
Classical Physics And Quantum Loops, Barry R. Holstein, John Donoghue
John Donoghue
The standard picture of the loop expansion associates a factor of h-bar with each loop, suggesting that the tree diagrams are to be associated with classical physics, while loop effects are quantum mechanical in nature. We discuss examples wherein classical effects arise from loop contributions and display the relationship between the classical terms and the long range effects of massless particles.
Parallel Dynamics And Computational Complexity Of Network Growth Models, Benjamin Machta, Jonathan Machta
Parallel Dynamics And Computational Complexity Of Network Growth Models, Benjamin Machta, Jonathan Machta
Physics Department Faculty Publication Series
No abstract provided.
Dynamics Of M-Theory Vacua, John Donoghue
Dynamics Of M-Theory Vacua, John Donoghue
John Donoghue
At very early times, the universe was not in a vacuum state. Under the assumtion that the deviation from equillibrium was large, in particular that it is higher than the scale of inflation, we analyse the conditions for local transitions between states that are related to different vacua. All pathways lead to an attractor solution of a description of the universe by eternal inflation with domains that have different low energy parameters. The generic case favors transitions between states that have significantly different parameters rather than jumps between nearby states in parameter space. I argue that the strong CP problem …
Department Of Physics Newsletter: Spring 2004, Bob Krotkov, Gerry Peterson, Monroe Rabin, Hajime Sakai
Department Of Physics Newsletter: Spring 2004, Bob Krotkov, Gerry Peterson, Monroe Rabin, Hajime Sakai
Physics Newsletters
No abstract provided.
Long Distance Chiral Corrections In Beta Meson Amplitudes, Jj Sanz-Cillero, Jf Donoghue, A Ross
Long Distance Chiral Corrections In Beta Meson Amplitudes, Jj Sanz-Cillero, Jf Donoghue, A Ross
Physics Department Faculty Publication Series
We discuss the chiral corrections to fB and BB with particular emphasis on determining the portion of the correction that arises from long distance physics. For very small pion and kaon masses all of the usual corrections are truly long distance, while for larger masses the long distance portion decreases. These chiral corrections have been used to extrapolate lattice calculations towards the physical region of lighter masses. We show in particular that the chiral extrapolation is better behaved if only the long distance portion of the correction is used. We also display the long distance portions of the infrared enhanced …
Weather And Climate, Rob Snyder
Weather And Climate, Rob Snyder
Science and Engineering Saturday Seminars
No abstract provided.
Commensurate Two-Component Bosons In An Optical Lattice: Ground State Phase Diagram, A Kuklov, N Prokof'ev, B Svistunov
Commensurate Two-Component Bosons In An Optical Lattice: Ground State Phase Diagram, A Kuklov, N Prokof'ev, B Svistunov
Physics Department Faculty Publication Series
Two sorts of bosons in an optical lattice at commensurate filling factors can form five stable superfluid and insulating ground states with rich and nontrivial phase diagram. The structure of the ground state diagram is established by mapping a d-dimensional quantum system onto a (d+1)-dimensional classical loop-current model and Monte Carlo (MC) simulations of the latter. Surprisingly, the quantum phase diagram features, besides second-order lines, first-order transitions and two multicritical points. We explain why first-order transitions are generic for models with pairing interactions using microscopic and mean-field (MF) arguments. In some cases, the MC results strongly deviate from the MF …
Truncated-Determinant Diagrammatic Monte Carlo For Fermions With Contact Interaction, E Bourovski, Nikolai Prokof'ev, Boris Svistunov
Truncated-Determinant Diagrammatic Monte Carlo For Fermions With Contact Interaction, E Bourovski, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
For some models of interacting fermions the known solution to the notorious sign problem in Monte Carlo (MC) simulations is to work with macroscopic fermionic determinants; the price, however, is a macroscopic scaling of the numerical effort spent on elementary local updates. We find that the ratio of two macroscopic determinants can be found with any desired accuracy by considering truncated (local in space and time) matices. In this respect, MC for interacting fermionic systems becomes similar to that for the sign-problem-free bosonic systems with system-size independent update cost. We demonstrate the utility of the truncated-determinant method by simulating the …
Superfluid-Superfluid Phase Transitions In A Two-Component Bose-Einstein Condensate, A Kuklov, Nikolai Prokof'ev, Boris Svistunov
Superfluid-Superfluid Phase Transitions In A Two-Component Bose-Einstein Condensate, A Kuklov, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
Depending on the Hamiltonian parameters, two-component bosons in an optical lattice can form at least three different superfluid phases in which both components participate in the superflow: a (strongly interacting) mixture of two miscible superfluids (2SF), a paired superfluid (PSF) vacuum, and (at a commensurate total filling factor) the super-counter-fluid (SCF) state. We study the universal properties of the 2SF-PSF and 2SF-SCF quantum phase transitions and show that (i) they can be mapped onto each other and (ii) their universality class is identical to the (d+1)-dimensional normal-superfluid transition in a single-component liquid. The finite-temperature 2SF-PSF(SCF) transitions and the topological properties …
Conserved Gravitational Charges From Yano Tensors, David Kastor, Jennie Traschen
Conserved Gravitational Charges From Yano Tensors, David Kastor, Jennie Traschen
Physics Department Faculty Publication Series
The defining properties of Yano tensors naturally generalize those of Killing vectors to anti-symmetric tensor fields of arbitrary rank. We show how the Yano tensors of flat spacetime can be used to construct new, conserved gravitational charges for transverse asymptotically flat spacetimes. The relationship of these new charges to Yano tensors parallels that of ordinary ADM conserved charges to Killing vectors. Hence, we call them Y-ADM charges. A rank n Y-ADM charge is given by an integral over a co-dimension n slice of spatial infinity. In particular, a rank (p+1) Y-ADM charge in a p-brane spacetime is given by an …
Effects Of Counterion Fluctuations In A Polyelectrolyte Brush, Christian Santangelo, A.W.C. Lau
Effects Of Counterion Fluctuations In A Polyelectrolyte Brush, Christian Santangelo, A.W.C. Lau
Christian Santangelo
We investigate the effect of counterion fluctuations in a single polyelectrolyte brush in the absence of added salt by systematically expanding the counterion free energy about Poisson-Boltzmann mean-field theory. We find that for strongly charged brushes, there is a collapse regime in which the brush height decreases with increasing charge on the polyelectrolyte chains. The transition to this collapsed regime is similar to the liquid-gas transition, which has a first-order line terminating at a critical point. We find that, for monovalent counterions, the transition is discontinuous in theta solvent, while for multivalent counterions, the transition is generally continuous. For collapsed …
Distribution Of Counterions Near Discretely Charged Planes And Rods, M. L. Henle, Christian Santangelo, D. M. Patel, P. A. Pincus
Distribution Of Counterions Near Discretely Charged Planes And Rods, M. L. Henle, Christian Santangelo, D. M. Patel, P. A. Pincus
Christian Santangelo
Realistic charged macromolecules are characterized by discrete (rather than homogeneous) charge distributions. We investigate the effects of surface charge discretization on the counterion distribution at the level of mean-field theory using a two-state model. Both planar and cylindrical geometries are considered; for the latter case, we compare our results to numerical solutions of the full Poisson-Boltzmann equation. We find that the discretization of the surface charge can cause enhanced localization of the counterions near the surface; for charged cylinders, counterion condensation can exceed Oosawa-Manning condensation.
Structural And Computational Depth Of Diffusion Limited Aggregation, D. Tillberg, Jonathan Machta
Structural And Computational Depth Of Diffusion Limited Aggregation, D. Tillberg, Jonathan Machta
Jonathan Machta
Diffusion-limited aggregation (DLA) is studied from the perspective of computational complexity. A parallel algorithm is exhibited that requires a number of steps that scales as the depth of the tree defined by the cluster. The existence of this algorithm suggests a connection between a fundamental computational and structural property of DLA.
Long Distance Chiral Corrections In B Meson Amplitudes, Juan J. Sanz-Cillero, John Donoghue, Andreas Ross
Long Distance Chiral Corrections In B Meson Amplitudes, Juan J. Sanz-Cillero, John Donoghue, Andreas Ross
John Donoghue
We discuss the chiral corrections to f_B and B_B with particular emphasis on determining the portion of the correction that arises from long distance physics. For very small pion and kaon masses all of the usual corrections are truly long distance, while for larger masses the long distance portion decreases. These chiral corrections have been used to extrapolate lattice calculations towards the physical region of lighter masses. We show in particular that the chiral extrapolation is better behaved if only the long distance portion of the correction is used.
Precision Zeeman-Stark Spectroscopy Of The Metastable A(1)[Σ+3] State Of Pbo, David Kawall, F. Bay, S. Bickman, Y. Jiang, D. Demille
Precision Zeeman-Stark Spectroscopy Of The Metastable A(1)[Σ+3] State Of Pbo, David Kawall, F. Bay, S. Bickman, Y. Jiang, D. Demille
David Kawall
The metastable a(1)[Σ+3] state of PbO has been suggested as a suitable system in which to search for the electric dipole moment of the electron. We report here the development of experimental techniques allowing high-sensitivity measurements of Zeeman and Stark effects in this system, similar to those required for such a search. We observe Zeeman quantum beats in fluorescence from a vapor cell of PbO, with shot-noise limited extraction of the quantum beat frequencies, high counting rates, and long coherence times. We argue that improvement in sensitivity to the electron electric dipole moment by at least 2 orders of magnitude …
Truncated-Determinant Diagrammatic Monte Carlo For Fermions With Contact Interaction, E Bourovski, Nikolai Prokof'ev, Boris Svistunov
Truncated-Determinant Diagrammatic Monte Carlo For Fermions With Contact Interaction, E Bourovski, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
For some models of interacting fermions the known solution to the notorious sign problem in Monte Carlo (MC) simulations is to work with macroscopic fermionic determinants; the price, however, is a macroscopic scaling of the numerical effort spent on elementary local updates. We find that the ratio of two macroscopic determinants can be found with any desired accuracy by considering truncated (local in space and time) matices. In this respect, MC for interacting fermionic systems becomes similar to that for the sign-problem-free bosonic systems with system-size independent update cost. We demonstrate the utility of the truncated-determinant method by simulating the …
Hole Digging In Ensembles Of Tunneling Molecular Magnets, I Tupitsyn, P Stamp, N Prokof'ev
Hole Digging In Ensembles Of Tunneling Molecular Magnets, I Tupitsyn, P Stamp, N Prokof'ev
Physics Department Faculty Publication Series
The nuclear spin-mediated quantum relaxation of ensembles of tunneling magnetic molecules causes a “hole” to appear in the distribution of internal fields in the system. The form of this hole and its time evolution, are studied using Monte Carlo simulations. It is shown that the line shape of the tunneling hole in a partially depolarized sample must have a Lorentzian line shape. The short-time half-width ξo in Fe8 crystals should be ∼E0, the half-width of the nuclear spin multiplet, but this result is not generally true. The Lorentzian hole line shape and the short-time √t relaxation in weakly polarized samples …
Weakly Interacting Bose Gas In The Vicinity Of The Critical Point, Nikolai Prokof'ev, O Ruebenacker, Boris Svistunov
Weakly Interacting Bose Gas In The Vicinity Of The Critical Point, Nikolai Prokof'ev, O Ruebenacker, Boris Svistunov
Physics Department Faculty Publication Series
We consider a three-dimensional weakly interacting Bose gas in the fluctuation region (and its vicinity) of the normal-superfluid phase transition point. We establish relations between basic thermodynamic functions: density, n(T, ì), superfluid density ns(T, ì), and condensate density, ncnd(T, ì). Being universal for all weakly interacting |ø|4 systems, these relations are obtained from Monte Carlo simulations of the classical |ø|4 model on a lattice. Comparing with the mean-field results yields a quantitative estimate of the fluctuation region size. Away from the fluctuation region, on the superfluid side, all the data perfectly agree with the predictions of the quasicondensate mean field …
Superfluid-Insulator Transition In Commensurate Disordered Bosonic Systems: Large-Scale Worm Algorithm Simulations, Nikolai Prokof'ev, Boris Svistunov
Superfluid-Insulator Transition In Commensurate Disordered Bosonic Systems: Large-Scale Worm Algorithm Simulations, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
We report results of large-scale Monte Carlo simulations of superfluid-insulator transitions in disordered commensurate 2D bosonic systems. In the off-diagonal disorder case, we find that the transition is to a gapless incompressible insulator, and its dynamical critical exponent is z=1.5(2). In the diagonal-disorder case, we prove the conjecture that rare statistical fluctuations are inseparable from critical fluctuations on the largest scales and ultimately result in crossover to the generic universality class (apparently with z=2). However, even at strong disorder, the universal behavior sets in only at very large space-time distances. This explains why previous studies of smaller clusters mimicked a …
Detecting Supercounterfluidity By Ramsey Spectroscopy, A Kuklov, Nikolai Prokof'ev, Boris Svistunov
Detecting Supercounterfluidity By Ramsey Spectroscopy, A Kuklov, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
A two-component system of ultracold atoms in an optical lattice at integer total filling factor and strong enough onsite repulsion can form a supercounterfluid (SCF) phase, which can be viewed as the Bose-Einstein condensate (BEC) of pairs formed by particles of one sort and holes of another sort. In this quasimolecular BEC, no single-component BEC exists, and the net atomic flow is prohibited. We show that, in the case of the interconvertible species (like hyperfine states of Rb), the corresponding order parameter can be detected by spatially selective Ramsey spectroscopy. The method can be used, in particular, for revealing a …
Kelvin-Wave Cascade And Decay Of Superfluid Turbulence, E Kozik, Boris Svistunov
Kelvin-Wave Cascade And Decay Of Superfluid Turbulence, E Kozik, Boris Svistunov
Physics Department Faculty Publication Series
Kelvin waves (kelvons), the distortion waves on vortex lines, play a key part in the relaxation of superfluid turbulence at low temperatures. We present a weak-turbulence theory of kelvons. We show that nontrivial kinetics arises only beyond the local-induction approximation and is governed by three-kelvon collisions; a corresponding kinetic equation is derived. We prove the existence of Kolmogorov cascade and find its spectrum. The qualitative analysis is corroborated by numeric study of the kinetic equation. The application of the results to the theory of superfluid turbulence is discussed.
A Derivative Of The Gerasimov-Drell-Hearn Sum Rule, V Pascalutsa, Br Holstein, M Vanderhaeghen
A Derivative Of The Gerasimov-Drell-Hearn Sum Rule, V Pascalutsa, Br Holstein, M Vanderhaeghen
Physics Department Faculty Publication Series
We derive a sum rule which establishes a linear relation between a particle's anomalous magnetic moment and a quantity connected to the photoabsorption cross section. This quantity cannot be measured directly. However, it can be computed within a given theory. As an example, we demonstrate validity of the sum rule in QED at tree level—the renowned Schwinger's correction to the anomalous magnetic moment is readily reproduced. In the case of the strong interactions, we also consider the calculation of the nucleon magnetic moment within chiral theories.