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- Gravitational waves (2)
- Astronomy (1)
- Black hole physics (1)
- Cosmology (1)
- Diffractometer (1)
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- Evolution (1)
- Galaxies (1)
- Granular matter (1)
- Inelasticspectrometer (1)
- Jamming transition (1)
- Magneto-inertial fusion (1)
- Magnetothermodynamics (1)
- Miscellaneous (1)
- Monte Carlo simulation (1)
- Neutron (1)
- Neutron scattering (1)
- Packing structure (1)
- Pentagon-shaped particle (1)
- Pulsar timing arrays (1)
- Ray-tracing (1)
- Reflectometer (1)
- SSX (1)
- Stars (1)
- Swarthmore Spheromak Experiment (1)
- Virtual experiment (1)
Articles 1 - 14 of 14
Full-Text Articles in Physics
The Astrophysics Of Nanohertz Gravitational Waves, S. Burke-Spolaor, S. R. Taylor, M. Charisi, T. Dolch, J. S. Hazboun, A. M. Holgado, L. Z. Kelley, T. J. W. Lazio, D. R. Madison, N. Mcmann, C. M. F. Mingarelli, A. Rasskazov, X. Siemens, J. J. Simon, Tristan L. Smith
The Astrophysics Of Nanohertz Gravitational Waves, S. Burke-Spolaor, S. R. Taylor, M. Charisi, T. Dolch, J. S. Hazboun, A. M. Holgado, L. Z. Kelley, T. J. W. Lazio, D. R. Madison, N. Mcmann, C. M. F. Mingarelli, A. Rasskazov, X. Siemens, J. J. Simon, Tristan L. Smith
Physics & Astronomy Faculty Works
Pulsar timing array (PTA) collaborations in North America, Australia, and Europe, have been exploiting the exquisite timing precision of millisecond pulsars over decades of observations to search for correlated timing deviations induced by gravitational waves (GWs). PTAs are sensitive to the frequency band ranging just below 1 nanohertz to a few tens of microhertz. The discovery space of this band is potentially rich with populations of inspiraling supermassive black hole binaries, decaying cosmic string networks, relic post-inflation GWs, and even non-GW imprints of axionic dark matter. This article aims to provide an understanding of the exciting open science questions in …
Lisa For Cosmologists: Calculating The Signal-To-Noise Ratio For Stochastic And Deterministic Sources, Tristan L. Smith, R. R. Caldwell
Lisa For Cosmologists: Calculating The Signal-To-Noise Ratio For Stochastic And Deterministic Sources, Tristan L. Smith, R. R. Caldwell
Physics & Astronomy Faculty Works
We present the steps to forecast the sensitivity of the Laser Interferometer Space Antenna (LISA) to both a stochastic gravitational wave background and deterministic wave sources. We show how to use these expressions to estimate the precision with which LISA can determine parameters associated with these sources. Tools are included to enable easy calculation of the signal-to-noise ratio and draw sensitivity curves. Benchmark values are given for easy comparison and checking of methods in the case of three worked examples. The first benchmark is the threshold stochastic gravitational wave background ΩGWh2 that LISA can observe. The second is the signal-to-noise …
Realistic Sensitivity Curves For Pulsar Timing Arrays, J. S. Hazboun, J. D. Romano, Tristan L. Smith
Realistic Sensitivity Curves For Pulsar Timing Arrays, J. S. Hazboun, J. D. Romano, Tristan L. Smith
Physics & Astronomy Faculty Works
We construct realistic sensitivity curves for pulsar timing array searches for gravitational waves, incorporating both red and white noise contributions to individual pulsar noise spectra, and the effect of fitting to a pulsar timing model. We demonstrate the method on both simulated pulsars and a realistic array consisting of a subset of NANOGrav pulsars used in recent analyses. A comparison between the results presented here and measured upper limit curves from actual analyses shows agreement to tens of percent. The resulting sensitivity curves can be used to assess the detectability of predicted gravitational-wave signals in the nanohertz frequency band in …
Jamming Transition In Non-Spherical Particle Systems: Pentagons Versus Disks, Y. Zhao, J. Barés, H. Zheng, Cacey Stevens Bester, Y. Xu, J. E. S. Socolar, R. P. Behringer
Jamming Transition In Non-Spherical Particle Systems: Pentagons Versus Disks, Y. Zhao, J. Barés, H. Zheng, Cacey Stevens Bester, Y. Xu, J. E. S. Socolar, R. P. Behringer
Physics & Astronomy Faculty Works
We investigate the jamming transition in a quasi-2D granular material composed of regular pentagons or disks subjected to quasistatic uniaxial compression. We report six major findings based on experiments with monodisperse photoelastic particles with static friction coefficient μ≈1. (1) For both pentagons and disks, the onset of rigidity occurs when the average coordination number of non-rattlers, Znr, reaches 3, and the dependence of Znr on the packing fraction ϕ changes again when Znr reaches 4. (2) Though the packing fractions ϕc1 and ϕc2 at these transitions differ from run to run, for both shapes the data from all runs with …
Hasasia: A Python Package For Pulsar Timing Array Sensitivity Curves, J. S. Hazboun, J. D. Romano, Tristan L. Smith
Hasasia: A Python Package For Pulsar Timing Array Sensitivity Curves, J. S. Hazboun, J. D. Romano, Tristan L. Smith
Physics & Astronomy Faculty Works
No abstract provided.
Using A Primordial Gravitational Wave Background To Illuminate New Physics, R. R. Caldwell, Tristan L. Smith, D. G. E. Walker
Using A Primordial Gravitational Wave Background To Illuminate New Physics, R. R. Caldwell, Tristan L. Smith, D. G. E. Walker
Physics & Astronomy Faculty Works
A primordial spectrum of gravitational waves serves as a backlight to the relativistic degrees of freedom of the cosmological fluid. Any change in the particle physics content, due to a change of phase or freeze-out of a species, will leave a characteristic imprint on an otherwise featureless primordial spectrum of gravitational waves and indicate its early-Universe provenance. We show that a gravitational wave detector such as the Laser Interferometer Space Antenna would be sensitive to physics near 100 TeV in the presence of a sufficiently strong primordial spectrum. Such a detection could complement searches at newly proposed 100 km circumference …
Recent Developments Of Mcvine And Its Applications At Sns, J. Y. Y. Lin, F. Islam, G. Sala, I. Lumsden, Hillary L. Smith, M. Doucet, M. B. Stone, D. L. Abernathy, G. Ehlers, J. F. Ankner
Recent Developments Of Mcvine And Its Applications At Sns, J. Y. Y. Lin, F. Islam, G. Sala, I. Lumsden, Hillary L. Smith, M. Doucet, M. B. Stone, D. L. Abernathy, G. Ehlers, J. F. Ankner
Physics & Astronomy Faculty Works
MCViNE is an open source, object-oriented Monte Carlo neutron ray-tracing simulation software package. Its design allows for flexible, hierarchical representations of sophisticated instrument components such as detector systems, and samples with a variety of shapes and scattering kernels. Recently this flexible design has enabled several applications of MCViNE simulations at the Spallation Neutron Source (SNS) at Oak Ridge National Lab, including assisting design of neutron instruments at the second target station and design of novel sample environments, as well as studying effects of instrument resolution and multiple scattering. Here we provide an overview of the recent developments and new features …
Recent Developments Of Mcvine And Its Applications At Sns, J. Y. Y. Lin, F. Islam, G. Sala, I. Lumsden, Hillary L. Smith, M. Doucet, M. B. Stone, D. L. Abernathy, G. Ehlers, J. F. Ankner, G. E. Granroth
Recent Developments Of Mcvine And Its Applications At Sns, J. Y. Y. Lin, F. Islam, G. Sala, I. Lumsden, Hillary L. Smith, M. Doucet, M. B. Stone, D. L. Abernathy, G. Ehlers, J. F. Ankner, G. E. Granroth
Physics & Astronomy Faculty Works
MCViNE is an open source, object-oriented Monte Carlo neutron ray-tracing simulation software package. Its design allows for flexible, hierarchical representations of sophisticated instrument components such as detector systems, and samples with a variety of shapes and scattering kernels. Recently this flexible design has enabled several applications of MCViNE simulations at the Spallation Neutron Source (SNS) at Oak Ridge National Lab, including assisting design of neutron instruments at the second target station and design of novel sample environments, as well as studying effects of instrument resolution and multiple scattering. Here we provide an overview of the recent developments and new features …
Bridging The Gaps: How Students Seek Disciplinary Coherence In Introductory Physics For Life Science, Benjamin D. Geller , '01, J. Gouvea, B. W. Dreyfus, V. Sawtelle, C. Turpen, E. F. Redish
Bridging The Gaps: How Students Seek Disciplinary Coherence In Introductory Physics For Life Science, Benjamin D. Geller , '01, J. Gouvea, B. W. Dreyfus, V. Sawtelle, C. Turpen, E. F. Redish
Physics & Astronomy Faculty Works
Students in one discipline often receive their scientific training from faculty in other disciplines. As a result of tacit disciplinary differences, especially as implemented in courses at the introductory college level, such students can have difficulty in understanding the nature of the knowledge they are learning in a discipline that they do not identify as their own. We developed a course in introductory physics for life science (IPLS) students that attempts to help them cross disciplinary boundaries. By analyzing student reasoning during recitation sections and interviews, we identified three broad ways in which students in our course meaningfully crossed boundaries: …
Making Energy Relevant: The Role Of Free Energy In Introductory Physics, Benjamin D. Geller , '01, A. R. Daane
Making Energy Relevant: The Role Of Free Energy In Introductory Physics, Benjamin D. Geller , '01, A. R. Daane
Physics & Astronomy Faculty Works
Free energy is a non-conserved quantity that is of fundamental importance in biochemistry and sociopolitical discourse, but one that does not often get discussed in introductory physics classrooms. While many canonical representations of energy that are encountered in introductory physics (energy bar charts, energy pie charts, etc.) foster ideas about energy that are productive for learners in a wide range of contexts, they have limited utility in contexts where free energy is an important consideration. In this study, we describe how learners who encounter canonical representations of energy in introductory physics develop a deep conviction that energy is conserved, and …
Early Dark Energy Can Resolve The Hubble Tension, V. Poulin, Tristan L. Smith, T. Karwal, M. Kamionkowski
Early Dark Energy Can Resolve The Hubble Tension, V. Poulin, Tristan L. Smith, T. Karwal, M. Kamionkowski
Physics & Astronomy Faculty Works
Early dark energy (EDE) that behaves like a cosmological constant at early times (redshifts z≳3000) and then dilutes away like radiation or faster at later times can solve the Hubble tension. In these models, the sound horizon at decoupling is reduced resulting in a larger value of the Hubble parameter H0 inferred from the cosmic microwave background (CMB). We consider two physical models for this EDE, one involving an oscillating scalar field and another a slowly rolling field. We perform a detailed calculation of the evolution of perturbations in these models. A Markov Chain Monte Carlo search of the parameter …
Magnetothermodynamics: An Experimental Study Of The Equations Of State Applicable To A Magnetized Plasma, M. Kaur, Michael R. Brown, A. D. Light
Magnetothermodynamics: An Experimental Study Of The Equations Of State Applicable To A Magnetized Plasma, M. Kaur, Michael R. Brown, A. D. Light
Physics & Astronomy Faculty Works
Measuring the equations of state of a compressed magnetized plasma is important for both advancing fusion experiments and understanding natural systems such as stellar winds. In this paper, we present results from our experiments on the thermodynamics of compressed magnetized plasmas; we call these studies “magnetothermodynamics.” In these experiments, we generate parcels of relaxed, magnetized plasma at one end of the linear Swarthmore Spheromak eXperimental device and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. Instances of ion heating during compression are identified by constructing a pressure-volume diagram using …
Probing Spatial Variation Of The Fine-Structure Constant Using The Cmb, Tristan L. Smith, D. Grin, David B. Robinson , '19, Davy Qi , '19
Probing Spatial Variation Of The Fine-Structure Constant Using The Cmb, Tristan L. Smith, D. Grin, David B. Robinson , '19, Davy Qi , '19
Physics & Astronomy Faculty Works
The fine-structure constant, α, controls the strength of the electromagnetic interaction. There are extensions of the standard model in which α is dynamical on cosmological length and time scales. The physics of the cosmic microwave background (CMB) depends on the value of α. The effects of spatial variation in α on the CMB are similar to those produced by weak lensing: smoothing of the power spectrum, and generation of non-Gaussian features. These would induce a bias to estimates of the weak-lensing potential power spectrum of the CMB. Using this effect, Planck measurements of the temperature and polarization power spectrum, as …
Magnetothermodynamics In Ssx: Measuring The Equations Of State Of A Compressible Magnetized Plasma, Michael R. Brown, M. Kaur
Magnetothermodynamics In Ssx: Measuring The Equations Of State Of A Compressible Magnetized Plasma, Michael R. Brown, M. Kaur
Physics & Astronomy Faculty Works
Magnetothermodynamics is the study of compression and expansion of magnetized plasma with an eye toward identifying equations of state (EOSs) for magneto-inertial fusion experiments. We present recent results from Swarthmore Spheromak Experiment (SSX) experiments on the thermodynamics of compressed magnetized plasmas called Taylor states. In these experiments, we generate twisted flux ropes of magnetized, relaxed plasma accelerated from one end of a 1.5-m-long copper flux conserver and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. The instances of ion heating during compression are identified by constructing a pressure-volume diagram …