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Articles 1 - 30 of 33
Full-Text Articles in Physical Sciences and Mathematics
Reevaluating The Cosmological Origin Of Dark Matter, Scott Watson
Reevaluating The Cosmological Origin Of Dark Matter, Scott Watson
Physics - All Scholarship
The origin of dark matter as a thermal relic offers a compelling way in which the early universe was initially populated by dark matter. Alternative explanations typically appear exotic compared to the simplicity of thermal production. However, recent observations and progress from theory suggest that it may be necessary to be more critical. This is important because ongoing searches probing the microscopic properties of dark matter typically rely on the assumption of dark matter as a single, unique, thermal relic. On general grounds I will argue that non-thermal production of dark matter seems to be a robust prediction of physics …
Aether Unleashed, Christian Armendariz-Picon, Alberto Diez-Tejedor
Aether Unleashed, Christian Armendariz-Picon, Alberto Diez-Tejedor
Physics - All Scholarship
We follow a low-energy effective theory approach to identify the general class of theories that describes a vector field (of unconstrained norm) coupled to gravity. The resulting set may be regarded as a generalization of the conventional vector-tensor theories, and as a high-momentum completion of aether models. We study the conditions that a viable cosmology, Newtonian limit and absence of classical and quantum instabilities impose on the parameters of our class of models, and compare these constraints with those derived in previously studied and related cases. The most stringent conditions arise from the quantum stability of the theory, which allows …
Reducing Microwave Loss In Superconducting Resonators Due To Trapped Vortices, Britton Plourde, C. Song, M. P. Defeo, Kang Yu
Reducing Microwave Loss In Superconducting Resonators Due To Trapped Vortices, Britton Plourde, C. Song, M. P. Defeo, Kang Yu
Physics - All Scholarship
Microwave resonators with high quality factors have enabled many recent breakthroughs with superconducting qubits and photon detectors, typically operated in shielded environments to reduce the ambient magnetic field. Insufficient shielding or pulsed control fields can introduce vortices, leading to reduced quality factors, although increased pinning can mitigate this effect. A narrow slot etched into the resonator surface provides a straightforward method for pinning enhancement without otherwise affecting the resonator. Resonators patterned with such a slot exhibited over an order of magnitude reduction in the excess loss due to vortices compared with identical resonators from the same film with no slot.
Exact Algorithm For Sampling The 2d Ising Spin Glass, Alan Middleton, Creighton K. Thomas
Exact Algorithm For Sampling The 2d Ising Spin Glass, Alan Middleton, Creighton K. Thomas
Physics - All Scholarship
A sampling algorithm is presented that generates spin glass configurations of the 2D Edwards-Anderson Ising spin glass at finite temperature, with probabilities proportional to their Boltzmann weights. Such an algorithm overcomes the slow dynamics of direct simulation and can be used to study long-range correlation functions and coarse-grained dynamics. The algorithm uses a correspondence between spin configurations on a regular lattice and dimer (edge) coverings of a related graph: Wilson's algorithm [D. B. Wilson, Proc. 8th Symp. Discrete Algorithms 258, (1997)] for sampling dimer coverings on a planar lattice is adapted to generate samplings for the dimer problem corresponding to …
Supersymmetric Lattices - A Brief Introduction, Simon Catterall
Supersymmetric Lattices - A Brief Introduction, Simon Catterall
Physics - All Scholarship
Recently, new theoretical ideas have allowed the construction of lattice actions which are explicitly invariant under one or more supersymmetries. These theories are local and free of doublers and in the case of Yang-Mills theories also possess exact gauge invariance. In this talk these ideas are reviewed with particular emphasis being placed on {\cal N}=4 super Yang-Mills theory.
Probes Of Nearly Conformal Behavior In Lattice Simulations Of Minimal Walking Technicolor, Simon Catterall, Joel Giedt, Francesco Sannino, Joe Schneible
Probes Of Nearly Conformal Behavior In Lattice Simulations Of Minimal Walking Technicolor, Simon Catterall, Joel Giedt, Francesco Sannino, Joe Schneible
Physics - All Scholarship
We present results from high precision, large volume simulations of the lattice gauge theory corresponding to minimal walking technicolor. We find evidence that the pion decay constant vanishes in the infinite volume limit and that the dependence of the chiral condensate on quark mass m_q is inconsistent with spontaneous symmetry breaking. These findings are consistent with the all-orders beta function prediction as well as the Schroedinger functional studies that indicate the existence of a nontrivial infrared fixed point.
Microboone: A New Liquid Argon Time Projection Chamber Experiment, Mitchell Soderberg
Microboone: A New Liquid Argon Time Projection Chamber Experiment, Mitchell Soderberg
Physics - All Scholarship
Liquid Argon Time Projection Chamber detectors are well suited to study neutrino interactions, and are an intriguing option for future massive detectors capable of measuring the parameters that characterize neutrino oscillations. These detectors combine fine-grained tracking with calorimetry, allowing for excellent imaging and particle identification ability. In this talk the details of the MicroBooNE experiment, a 175 ton LArTPC which will be exposed to Fermilab's Booster Neutrino Beamline starting in 2011, will be presented. The ability of MicroBooNE to differentiate electrons from photons gives the experiment unique capabilities in low energy neutrino interaction measurements.
Liquid-Argon Time Projection Chambers In The U.S, Mitchell Soderberg
Liquid-Argon Time Projection Chambers In The U.S, Mitchell Soderberg
Physics - All Scholarship
Liquid Argon Time Projection Chamber (LAr TPC) detectors are ideally suited for studying neutrino interactions and probing the parameters that characterize neutrino oscillations. The ability to drift ionization particles over long distances in purified argon and to trigger on abundant scintillation light allows for excellent particle identification and triggering capability. Recent U.S. based work in the development of LAr TPC technology for massive kiloton size detectors will be discussed in this talk, including details of the ArgoNeuT (Argon Neutrino Test) test-beam project, which is a 175 liter LAr TPC exposed to Fermilab's NuMI neutrino beamline.
Argoneut: A Liquid Argon Time Projection Chamber Test In The Numi Beamline, Mitchell Soderberg
Argoneut: A Liquid Argon Time Projection Chamber Test In The Numi Beamline, Mitchell Soderberg
Physics - All Scholarship
Liquid Argon Time Projection Chamber detectors are ideally suited for studying neutrino interactions and probing the parameters that characterize neutrino oscillations. The ability to drift ionization particles over long distances in purified argon and to trigger on abundant scintillation light allows for excellent particle identification and triggering capability. In these proceedings the details of the ArgoNeuT test-beam project will be presented after a brief introduction to the detector technique. ArgoNeuT is a 175 liter detector exposed to Fermilab's NuMI neutrino beamline. The first neutrino interactions observed in ArgoNeuT will be presented, along with discussion of the various physics analyses to …
Extracting Black Hole Physics From The Lattice, Simon Catterall, Toby Wiseman
Extracting Black Hole Physics From The Lattice, Simon Catterall, Toby Wiseman
Physics - All Scholarship
We perform lattice simulations of N D0-branes at finite temperature in the decoupling limit, namely 16 supercharge SU(N) Yang-Mills quantum mechanics in the 't Hooft limit. At low temperature this theory is conjectured to be dual to certain supergravity black holes. We emphasize that the existence of a non-compact moduli space renders the partition function of the quantum mechanics theory divergent, and we perform one loop calculations that demonstrate this explicitly. In consequence we use a scalar mass term to regulate this divergence and argue that the dual black hole thermodynamics may be recovered in the appropriate large N limit …
Perturbed S3 Neutrinos, Joseph Schechter, Renata Jora, M. Naeem Shahid
Perturbed S3 Neutrinos, Joseph Schechter, Renata Jora, M. Naeem Shahid
Physics - All Scholarship
We study the effects of the perturbation which violates the permutation symmetry of three Majorana neutrinos but preserves the well known (23) interchange symmetry. This is done in the presence of an arbitrary Majorana phase which serves to insure the degeneracy of the three neutrinos at the unperturbed level.
The Hunt For New Physics At The Large Hadron Collider, Joseph Schechter, Pran Nath
The Hunt For New Physics At The Large Hadron Collider, Joseph Schechter, Pran Nath
Physics - All Scholarship
We study the effects of the perturbation which violates the permutation symmetry of three Majorana neutrinos but preserves the well known (23) interchange symmetry. This is done in the presence of an arbitrary Majorana phase which serves to insure the degeneracy of the three neutrinos at the unperturbed level.
Exact Lattice Supersymmetry, Simon Catterall, David B. Kaplan, Mithat Unsal
Exact Lattice Supersymmetry, Simon Catterall, David B. Kaplan, Mithat Unsal
Physics - All Scholarship
We provide an introduction to recent lattice formulations of supersymmetric theories which are invariant under one or more real supersymmetries at nonzero lattice spacing. These include the especially interesting case of {\cal N}=4 SYM in four dimensions. We discuss approaches based both on twisted supersymmetry and orbifold-deconstruction techniques and show their equivalence in the case of gauge theories. The presence of an exact supersymmetry reduces and in some cases eliminates the need for fine tuning to achieve a continuum limit invariant under the full supersymmetry of the target theory. We discuss open problems.
A Non-Thermal Wimp Miracle, Scott Watson, Bobby Samir Acharya, Gordon Kane, Piyush Kumar
A Non-Thermal Wimp Miracle, Scott Watson, Bobby Samir Acharya, Gordon Kane, Piyush Kumar
Physics - All Scholarship
Light scalar fields with only gravitational strength couplings are typically present in UV complete theories of physics beyond the Standard Model. In the early universe it is natural for these fields to dominate the energy density, and their subsequent decay, if prior to BBN, will typically yield some dark matter particles in their decay products. In this paper we make the observation that a Non-thermal WIMP `Miracle' may result: that is, in the simplest solution to the cosmological moduli problem, non-thermally produced WIMPs can naturally account for the observed dark matter relic density. Such a solution may be generic in …
Pamela Satellite Data As A Signal Of Non-Thermal Wino Lsp Dark Matter, Scott Watson, Gordon Kane, Ran Lu
Pamela Satellite Data As A Signal Of Non-Thermal Wino Lsp Dark Matter, Scott Watson, Gordon Kane, Ran Lu
Physics - All Scholarship
Satellite data is accumulating that suggests and constrains dark matter physics. We argue there is a very well motivated theoretical preexisting framework consistent with dark matter annihilation being observed by the PAMELA satellite detector. The dark matter is (mainly) the neutral W boson superpartner, the wino with mass below 200 GeV. Using the program GALPROP we study the annihilation products and backgrounds together. Antimatter and gammas from annihilating winos contribute below this energy. We explain why PAMELA data does not imply no antiproton signal was observed by PAMELA or earlier experiments, and explain why the antiproton analysis was misunderstood by …
Two-Dimensional Matter: Order, Curvature And Defects, Mark Bowick, Luca Giomi
Two-Dimensional Matter: Order, Curvature And Defects, Mark Bowick, Luca Giomi
Physics - All Scholarship
Many systems in nature and the synthetic world involve ordered arrangements of units on two-dimensional surfaces. We review here the fundamental role payed by both the topology of the underlying surface and its detailed curvature. Topology dictates certain broad features of the defect structure of the ground state but curvature-driven energetics controls the detailed structured of ordered phases. Among the surprises are the appearance in the ground state of structures that would normally be thermal excitations and thus prohibited at zero temperature. Examples include excess dislocations in the form of grain boundary scars for spherical crystals above a minimal system …
Gauged Linear Sigma Model And Pion-Pion Scattering, Joseph Schechter, Amir H. Fariborz, Nae Woong Park, M. Naeem Shahid
Gauged Linear Sigma Model And Pion-Pion Scattering, Joseph Schechter, Amir H. Fariborz, Nae Woong Park, M. Naeem Shahid
Physics - All Scholarship
A simple gauged linear sigma model with several parameters to take the symmetry breaking and the mass differences between the vector meson and the axial vector meson into account is considered here as a possibly useful template for the role of a light scalar in QCD as well as for (at a different scale) an effective Higgs sector for some recently proposed walking technicolor models. An analytic procedure is first developed for relating the Lagrangian parameters to four well established (in the QCD application) experimental inputs. One simple equation distinguishes three different cases:1. QCD with axial vector particle heavier than …
Microwave Response Of Vortices In Superconducting Thin Films Of Re And Al, Britton Plourde, C. Song, T. W. Heitmann, M. P. Defeo, Kang Yu
Microwave Response Of Vortices In Superconducting Thin Films Of Re And Al, Britton Plourde, C. Song, T. W. Heitmann, M. P. Defeo, Kang Yu
Physics - All Scholarship
Vortices in superconductors driven at microwave frequencies exhibit a response related to the interplay between the vortex viscosity, pinning strength, and flux creep effects. At the same time, the trapping of vortices in superconducting microwave resonant circuits contributes excess loss and can result in substantial reductions in the quality factor. Thus, understanding the microwave vortex response in superconducting thin films is important for the design of such circuits, including superconducting qubits and photon detectors, which are typically operated in small, but non-zero, magnetic fields. By cooling in fields of the order of 100 $\mu$T and below, we have characterized the …
Simulation Of The Zero Temperature Behavior Of A 3-Dimensional Elastic Medium, Alan Middleton, David Mcnamara, Chen Zeng
Simulation Of The Zero Temperature Behavior Of A 3-Dimensional Elastic Medium, Alan Middleton, David Mcnamara, Chen Zeng
Physics - All Scholarship
We have performed numerical simulation of a 3-dimensional elastic medium, with scalar displacements, subject to quenched disorder. We applied an efficient combinatorial optimization algorithm to generate exact ground states for an interface representation. Our results indicate that this Bragg glass is characterized by power law divergences in the structure factor $S(k)\sim A k^{-3}$. We have found numerically consistent values of the coefficient $A$ for two lattice discretizations of the medium, supporting universality for $A$ in the isotropic systems considered here. We also examine the response of the ground state to the change in boundary conditions that corresponds to introducing a …
Smectic Polymer Vesicles, Mark Bowick, Lin Jia, Xiangjun Xing
Smectic Polymer Vesicles, Mark Bowick, Lin Jia, Xiangjun Xing
Physics - All Scholarship
Polymer vesicles are stable robust vesicles made from block copolymer amphiphiles. Recent progress in the chemical design of block copolymers opens up the exciting possibility of creating a wide variety of polymer vesicles with varying fine structure, functionality and geometry. Polymer vesicles not only constitute useful systems for drug delivery and micro/nano-reactors but also provide an invaluable arena for exploring the ordering of matter on curved surfaces embedded in three dimensions. By choosing suitable liquid-crystalline polymers for one of the copolymer components one can create vesicles with smectic stripes. Smectic order on shapes of spherical topology inevitably possesses topological defects …
Cmbpol Mission Concept Study: Probing Inflation With Cmb Polarization, Scott Watson, Daniel Baumann, Mark G. Jackson, Peter Adshead
Cmbpol Mission Concept Study: Probing Inflation With Cmb Polarization, Scott Watson, Daniel Baumann, Mark G. Jackson, Peter Adshead
Physics - All Scholarship
We summarize the utility of precise cosmic microwave background (CMB) polarization measurements as probes of the physics of inflation. We focus on the prospects for using CMB measurements to differentiate various inflationary mechanisms. In particular, a detection of primordial B-mode polarization would demonstrate that inflation occurred at a very high energy scale, and that the inflaton traversed a super-Planckian distance in field space. We explain how such a detection or constraint would illuminate aspects of physics at the Planck scale. Moreover, CMB measurements can constrain the scale-dependence and non-Gaussianity of the primordial fluctuations and limit the possibility of a significant …
A Regenerable Filter For Liquid Argon Purification, Mitchell Soderberg, A. Curioni
A Regenerable Filter For Liquid Argon Purification, Mitchell Soderberg, A. Curioni
Physics - All Scholarship
A filter system for removing electronegative impurities from liquid argon is described. The active components of the filter are adsorbing molecular sieve and activated-copper-coated alumina granules. The system is capable of purifying liquid argon to an oxygen-equivalent impurity concentration of better than 30 parts per trillion, corresponding to an electron drift lifetime of at least 10 ms. Reduction reactions that occur at about 250 degrees Celsius allow the filter material to be regenerated in-situ through a simple procedure. In the following work we describe the filter design, performance, and regeneration process.
Observing The Evolution Of The Universe, Scott Watson
Observing The Evolution Of The Universe, Scott Watson
Physics - All Scholarship
How did the universe evolve? The fine angular scale (l>1000) temperature and polarization anisotropies in the CMB are a Rosetta stone for understanding the evolution of the universe. Through detailed measurements one may address everything from the physics of the birth of the universe to the history of star formation and the process by which galaxies formed. One may in addition track the evolution of the dark energy and discover the net neutrino mass. We are at the dawn of a new era in which hundreds of square degrees of sky can be mapped with arcminute resolution and sensitivities …
Global Aspects Of The Scalar Meson Puzzle, Joseph Schechter, Amir H. Fariborz, Renata Jora
Global Aspects Of The Scalar Meson Puzzle, Joseph Schechter, Amir H. Fariborz, Renata Jora
Physics - All Scholarship
A generalized linear sigma model for low energy QCD is employed to study the quark structure of eight low lying scalar isomultiplets as well as eight low lying pseudoscalar isomultiplets. The model, building on earlier work, assumes the possible mixing of quark anti-quark states with others made of two quarks and two antiquarks. No {\it a priori} assumption is made about the quark contents of the states, which emerge as predictions. An amusing and contrasting pattern for the quark structure is found; the lighter conventional pseudoscalars are, as expected, primarily of two quark type whereas the lighter scalars have very …
First Results From Simulations Of Supersymmetric Lattices, Simon Catterall
First Results From Simulations Of Supersymmetric Lattices, Simon Catterall
Physics - All Scholarship
We conduct the first numerical simulations of lattice theories with exact supersymmetry arising from the orbifold constructions of \cite{Cohen:2003xe,Cohen:2003qw,Kaplan:2005ta}. We consider the \cQ=4 theory in D=0,2 dimensions and the \cQ=16 theory in D=0,2,4 dimensions. We show that the U(N) theories do not possess vacua which are stable non-perturbatively, but that this problem can be circumvented after truncation to SU(N). We measure the distribution of scalar field eigenvalues, the spectrum of the fermion operator and the phase of the Pfaffian arising after integration over the fermions. We monitor supersymmetry breaking effects by measuring a simple Ward identity. Our results indicate that …
Anti-De Sitter Space From Supersymmetric Gauge Theory, Simon Catterall
Anti-De Sitter Space From Supersymmetric Gauge Theory, Simon Catterall
Physics - All Scholarship
We construct a four dimensional Yang-Mills theory with {\cal N}=4 twisted supersymmetry whose classical vacua correspond to four dimensional anti-de Sitter space. The theory utilizes a complex gauge field whose real part is a spin connection which is used to enforce local Lorentz invariance. The imaginary part of the connection can then be interpreted as a vierbein. The topological construction ensures that the partition function and classical vacua are independent of the background geometry. Additionally a supersymmetric and gauge invariant lattice construction is possible yielding a non-perturbative definition of the theory.
Hole Drift Mobility Measurements On A-Si:H Using Surface And Uniformly Absorbed Illumination, Steluta A. Dinca, Eric A. Schiff, S. Guha, Baojie Yan, Jeff Yang
Hole Drift Mobility Measurements On A-Si:H Using Surface And Uniformly Absorbed Illumination, Steluta A. Dinca, Eric A. Schiff, S. Guha, Baojie Yan, Jeff Yang
Physics - All Scholarship
The standard, time-of-flight method for measuring drift mobilities in semiconductors uses strongly absorbed illumination to create a sheet of photocarriers near an electrode interface. This method is problematic for solar cells deposited onto opaque substrates, and in particular cannot be used for hole photocarriers in hydrogenated amorphous silicon (a-Si:H) solar cells using stainless steel substrates. In this paper we report on the extension of the time-of-flight method that uses weakly absorbed illumination. We measured hole drift-mobilities on seven a-Si:H nip solar cells using strongly and weakly absorbed illumination incident through the n-layer. For thinner devices from two laboratories, the drift-mobilities …
Solvent-Washable Polymer Templated Synthesis Of Mesoporous Materials And Solic-Acid Nanocatalysts In One-Pot, Richard E. Mishler Ii, Ankush V. Biradar, Cole T. Duncan, Eric A. Schiff, Tewodros Asefa
Solvent-Washable Polymer Templated Synthesis Of Mesoporous Materials And Solic-Acid Nanocatalysts In One-Pot, Richard E. Mishler Ii, Ankush V. Biradar, Cole T. Duncan, Eric A. Schiff, Tewodros Asefa
Physics - All Scholarship
We report a new and simple one-pot synthetic method to produce mesoporous silica and nanoporous solid acid catalyst capable of catalyzing pinacole-pinacolone rearrangement and esterification reactions, by preparing a solvent washable phosphonated triblock copolymer template and self-assembling it in the presence of alkoxysilane.
Feasibility Of Measuring The Shapiro Time Delay Over Meter-Scale Distances, Stefan Ballmer, S. Marka, P. Shawhan
Feasibility Of Measuring The Shapiro Time Delay Over Meter-Scale Distances, Stefan Ballmer, S. Marka, P. Shawhan
Physics - All Scholarship
The time delay of light as it passes by a massive object, first calculated by Shapiro in 1964, is a hallmark of the curvature of space-time. To date, all measurements of the Shapiro time delay have been made over solar-system distance scales. We show that the new generation of kilometer-scale laser interferometers being constructed as gravitational wave detectors, in particular Advanced LIGO, will in principle be sensitive enough to measure variations in the Shapiro time delay produced by a suitably designed rotating object placed near the laser beam. We show that such an apparatus is feasible (though not easy) to …
Is The Spacetime Metric Euclidean Rather Than Lorentzian?, Rafael D. Sorkin
Is The Spacetime Metric Euclidean Rather Than Lorentzian?, Rafael D. Sorkin
Physics - All Scholarship
My answer to the question in the title is "No". In support of this point of view, we analyze some examples of saddle-point methods, especially as applied to quantum "tunneling" in nonrelativistic particle mechanics and in cosmology. Along the way we explore some of the interrelationships among different ways of thinking about path-integrals and saddle-point approximations to them.