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Implications Of D-0-(D)Over-Bar(0) Mixing For New Physics, E Golowich, J Hewett, S Pakvasa, Aa Petrov
Implications Of D-0-(D)Over-Bar(0) Mixing For New Physics, E Golowich, J Hewett, S Pakvasa, Aa Petrov
Physics Department Faculty Publication Series
We provide a comprehensive, up-to-date analysis of possible new physics contributions to the mass difference ΔMD in D0-D̅ 0 mixing. We consider the most general low-energy effective Hamiltonian and include leading-order QCD running of effective operators. We then explore an extensive list of possible new physics models that can generate these operators, which we organize as including extra fermions, extra gauge bosons, extra scalars, extra space dimensions and extra symmetries. For each model we place restrictions on the allowed parameter space using the recent evidence for observation of D meson mixing. In many scenarios, we find strong constraints that surpass …
Bold Diagrammatic Monte Carlo Technique: When The Sign Problem Is Welcome, N Prokof'ev, B Svistunov
Bold Diagrammatic Monte Carlo Technique: When The Sign Problem Is Welcome, N Prokof'ev, B Svistunov
Physics Department Faculty Publication Series
We introduce a Monte Carlo scheme for sampling a bold-line diagrammatic series specifying an unknown function in terms of itself. The range of convergence of this bold(-line) diagrammatic Monte Carlo (BMC) technique is significantly broader than that of a simple iterative scheme for solving integral equations. With the BMC technique, a moderate “sign problem” turns out to be an advantage in terms of the convergence of the process. For an illustrative purpose, we solve the one-particle s-scattering problem. As an important application, we obtain the T matrix for a Fermi polaron (one spin-down particle interacting with the spin-up fermionic sea).
Superfluidity Of Grain Boundaries In Solid 4he, L Pollet, M Boninsegni, A Kuklov, Nikolai Prokof'ev, Boris Svistunov, M Troyer
Superfluidity Of Grain Boundaries In Solid 4he, L Pollet, M Boninsegni, A Kuklov, Nikolai Prokof'ev, Boris Svistunov, M Troyer
Physics Department Faculty Publication Series
By large-scale quantum Monte Carlo simulations we show that grain boundaries in 4He crystals are generically superfluid at low temperature, with a transition temperature of the order of ∼0.5 K at the melting pressure; nonsuperfluid grain boundaries are found only for special orientations of the grains. We also find that close vicinity to the melting line is not a necessary condition for superfluid grain boundaries, and a grain boundary in direct contact with the superfluid liquid at the melting curve is found to be mechanically stable and the grain-boundary superfluidity observed by Sasaki et al. [Science 313, 1098 (2006)] is …
The First Law For Boosted Kaluza-Klein Black Holes, David Kastor, Sourya Ray, Jennie Traschen
The First Law For Boosted Kaluza-Klein Black Holes, David Kastor, Sourya Ray, Jennie Traschen
Physics Department Faculty Publication Series
We study the thermodynamics of Kaluza-Klein black holes with momentum along the compact dimension, but vanishing angular momentum. These black holes are stationary, but non-rotating. We derive the first law for these spacetimes and find that the parameter conjugate to variations in the length of the compact direction is an effective tension, which generally differs from the ADM tension. For the boosted black string, this effective tension is always positive, while the ADM tension is negative for large boost parameter. We also derive two Smarr formulas, one that follows from time translation invariance, and a second one that holds only …
The Attractor Mechanism In Gauss-Bonnet Gravity, Mohamed Anber, David Kastor
The Attractor Mechanism In Gauss-Bonnet Gravity, Mohamed Anber, David Kastor
Physics Department Faculty Publication Series
We study extremal black hole solutions of D = 5 Gauss-Bonnet gravity coupled to a system of gauge and scalar fields. As in Einstein gravity, we find that the values of the scalar fields on the horizon must extremize a certain effective potential that depends on the black hole charges. If the matrix of second derivatives of the effective potential at this extremum has positive eigenvalues, we give evidence, based on a near horizon perturbative expansion, that the attractor mechanism continues to hold in this general class of theories. We numerically construct solutions to a particular simple single scalar field …
Giant Viscosity Enhancement In A Spin-Polarized Fermi Liquid, H Akimoto, Js Xia, D Candela, Wj Mullin, Ed Adams, Ns Sullivan
Giant Viscosity Enhancement In A Spin-Polarized Fermi Liquid, H Akimoto, Js Xia, D Candela, Wj Mullin, Ed Adams, Ns Sullivan
Physics Department Faculty Publication Series
The viscosity is measured for a Fermi liquid, a dilute 3He-4He mixture, under extremely high magnetic field/temperature conditions (B≤14.8 T, T≥1.5 mK). The spin-splitting energy μB is substantially greater than the Fermi energy kBTF; as a consequence the polarization tends to unity and s-wave quasiparticle scattering is suppressed for T≪TF. Using a novel composite vibrating-wire viscometer an enhancement of the viscosity is observed by a factor of more than 500 over its low-field value. Good agreement is found between the measured viscosity and theoretical predictions based upon a t-matrix formalism.
On-Site Number Statistics Of Ultracold Lattice Bosons, B Capogrosso-Sansone, E Kozik, Nikolai Prokof'ev, Boris Svistunov
On-Site Number Statistics Of Ultracold Lattice Bosons, B Capogrosso-Sansone, E Kozik, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
We study on-site occupation number fluctuations in a system of interacting bosons in an optical lattice. The ground-state distribution is obtained analytically in the limiting cases of strong and weak interaction, and by means of exact Monte Carlo simulations in the strongly correlated regime. As the interaction is increased, the distribution evolves from Poissonian in the noninteracting gas to a sharply peaked distribution in the Mott-insulator (MI) regime. In the special case of large occupation numbers, we demonstrate analytically and check numerically that there exists a wide interval of interaction strength, in which the on-site number fluctuations remain Gaussian and …
Charm Mixing - Theory, Eugene Golowich
Charm Mixing - Theory, Eugene Golowich
Physics Department Faculty Publication Series
We discuss Standard Model (SM) and New Physics (NP) descriptions of D0 mixing. The SM part of the discussion addresses both quark level and hadron level contributions. The NP part describes our recent works on the rate difference Delta Gamma_D and the mass difference Delta M_D. In particular, we describe how the recent experimental determination of Delta M_D is found to place tightened restrictions on parameter spaces for 17 of 21 NP models considered in a recent paper by Hewett, Pakvasa, Petrov and myself.
Nonlocal Quantum Effects With Bose-Einstein Condensates, F Laloe, Wj Mullin
Nonlocal Quantum Effects With Bose-Einstein Condensates, F Laloe, Wj Mullin
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 …
New Physics Contributions To The Lifetime Difference In D-0-(D)Over-Bar(0) Mixing, E Golowich, S Pakvasa, Aa Petrov
New Physics Contributions To The Lifetime Difference In D-0-(D)Over-Bar(0) Mixing, E Golowich, S Pakvasa, Aa Petrov
Physics Department Faculty Publication Series
We present the first general analysis of New Physics contributions to the D0-D̅ 0 lifetime difference (equivalently ΔΓD). We argue that New Physics (NP) contributions to |ΔC|=1 processes can dominate the lifetime difference in the flavor SU(3) limit. We provide several specific examples of models that produce sizable effects in ΔΓD for realistic values of light quark masses, even if such NP contributions are undetectable in the current round of D0 decay experiments. This makes ΔΓD a viable observable for studies of indirect effects of New Physics.
Luttinger Liquid In The Core Of A Screw Dislocation In Helium-4, M Boninsegni, Kuklov, Pollet, Nikolai Prokof'ev, Boris Svistunov, Troyer
Luttinger Liquid In The Core Of A Screw Dislocation In Helium-4, M Boninsegni, Kuklov, Pollet, Nikolai Prokof'ev, Boris Svistunov, Troyer
Physics Department Faculty Publication Series
On the basis of first-principles Monte Carlo simulations we find that the screw dislocation along the hexagonal axis of an hcp 4He crystal features a superfluid (at T→0) core. This is the first example of a regular quasi-one-dimensional supersolid—the phase featuring both translational and superfluid orders, and one of the cleanest cases of a Luttinger-liquid system. In contrast, the same type of screw dislocation in solid H2 is insulating.
On The Stabilization Of Ion Sputtered Surfaces, B Davidovitch
On The Stabilization Of Ion Sputtered Surfaces, B Davidovitch
Physics Department Faculty Publication Series
The classical theory of ion beam sputtering predicts the instability of a flat surface to uniform ion irradiation at any incidence angle. We relax the assumption of the classical theory that the average surface erosion rate is determined by a Gaussian response function representing the effect of the collision cascade, and consider the surface dynamics for other physically motivated response functions. We show that although instability of flat surfaces at any beam angle results from all Gaussian and a wide class of non-Gaussian erosive response functions, there exist classes of modifications to the response that can have a dramatic effect. …
Critical Behavior Of The Chayes–Machta–Swendsen–Wang Dynamics, Y Deng, T Garoni, J Machta, G Ossola, M Polin, A Sokal
Critical Behavior Of The Chayes–Machta–Swendsen–Wang Dynamics, Y Deng, T Garoni, J Machta, G Ossola, M Polin, A Sokal
Physics Department Faculty Publication Series
We study the dynamic critical behavior of the Chayes-Machta dynamics for the Fortuin-Kasteleyn random-cluster model, which generalizes the Swendsen-Wang dynamics for the q-state Potts model to noninteger q, in two and three spatial dimensions, by Monte Carlo simulation. We show that the Li-Sokal bound z≥α/ν is close to but probably not sharp in d=2 and is far from sharp in d=3, for all q. The conjecture z≥β/ν is false (for some values of q) in both d=2 and d=3.
What Makes A Crystal Supersolid?, Nikolai Prokof'ev
What Makes A Crystal Supersolid?, Nikolai Prokof'ev
Physics Department Faculty Publication Series
For nearly half a century the supersolid phase of matter has remained mysterious, not only eluding experimental observation, but also generating a great deal of controversy among theorists. The recent discovery of what is interpreted as a non-classical moment of inertia at low temperature in solid 4He [E. Kim and M.H.W. Chan, Nature 427 225 (2004a); E. Kim and M.H.W. Chan, Science 305 1941 (2004b); E. Kim and M.H.W. Chan, Phys. Rev. Lett. 97 115302 (2006); A.C. Clark and M.H.W. Chan, J. Low Temp. Phys. 138 853 (2005)] has elicited much excitement as a possible first observation of a supersolid …
Superfluid-Insulator And Roughening Transitions In Domain Walls, S Söyler, Capogrosso-Sansone, Nikolai Prokof'ev, Boris Svistunov
Superfluid-Insulator And Roughening Transitions In Domain Walls, S Söyler, Capogrosso-Sansone, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
We have performed quantum Monte Carlo simulations to investigate the superfluid behavior of one- and two-dimensional interfaces separating checkerboard solid domains. The system is described by the hard-core Bose-Hubbard Hamiltonian with nearest-neighbor interaction. In accordance with Burovski et al. [Phys. Rev. Lett. 94, 165301 (2005)] we find that (i) the interface remains superfluid in a wide range of interaction strength before it undergoes a superfluid-insulator transition; (ii) in one dimension, the transition is of the Kosterlitz-Thouless type and is accompanied by the roughening transition, driven by proliferation of charge-1∕2 quasiparticles; (iii) in two dimensions, the transition belongs to the three-dimensional …
Phase Diagram And Thermodynamics Of The Three-Dimensional Bose-Hubbard Model, B Capogrosso-Sansone, Nikolai Prokof'ev, Boris Svistunov
Phase Diagram And Thermodynamics Of The Three-Dimensional Bose-Hubbard Model, B Capogrosso-Sansone, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
We report results of quantum Monte Carlo simulations of the Bose-Hubbard model in three dimensions. Critical parameters for the superfluid-to-Mott-insulator transition are determined with significantly higher accuracy than has been done in the past. In particular, the position of the critical point at filling factor n=1 is found to be at (U∕t)c=29.34(2), and the insulating gap Δ is measured with accuracy of a few percent of the hopping amplitude t. We obtain the effective mass of particle and hole excitations in the insulating state—with explicit demonstration of the emerging particle-hole symmetry and relativistic dispersion law at the transition tip—along with …
Do Killing–Yano Tensors Form A Lie Algebra?, David Kastor, Sourya Ray, Jennie Traschen
Do Killing–Yano Tensors Form A Lie Algebra?, David Kastor, Sourya Ray, Jennie Traschen
Physics Department Faculty Publication Series
Killing–Yano tensors are natural generalizations of Killing vectors. We investigate whether Killing–Yano tensors form a graded Lie algebra with respect to the Schouten–Nijenhuis bracket. We find that this proposition does not hold in general, but that it does hold for constant curvature spacetimes. We also show that Minkowski and (anti)-deSitter spacetimes have the maximal number of Killing–Yano tensors of each rank and that the algebras of these tensors under the SN bracket are relatively simple extensions of the Poincaré and (A)dS symmetry algebras.
The Fine-Tuning Problems Of Particle Physics And Anthropic Mechanisms, John Donoghue
The Fine-Tuning Problems Of Particle Physics And Anthropic Mechanisms, John Donoghue
Physics Department Faculty Publication Series
Many of the classic problems of particle physics appear in a very different light when viewed from the perspective of the multiverse. Most importantly the two great ``fine tuning'' problems that motivate the field are far less serious when one accounts for the required anthropic constraints which exist in a multiverse. However, the challenge then becomes to construct a realistic physical theory of the multiverse and test it. I describe some phenomenology of the quark and lepton masses that may provide a window to the theory that underlies the multiverse.