155 research outputs found
Physics lab with professor Essick, ca. 1995
No full texthttps://rdc.reed.edu/v1/resources/6912d733-43e9-49ec-ab27-4579ffd6c68a/thumb/128.jpgPhysics professor John Essick and a student in the physics lab working with lazer equipment, ca. 1995
Nonparametric extensions of nuclear equations of state: probing the breakdown scale of relativistic mean-field theory
No full textPhenomenological calculations of the properties of dense matter, such as relativistic mean-field theories, represent a pathway to predicting the microscopic and macroscopic properties of neutron stars. However, such theories do not generically have well-controlled uncertainties and may break down within neutron stars. To faithfully represent the uncertainty in this breakdown scale, we develop a hybrid representation of the dense-matter equation of state, which assumes the form of a relativistic mean-field theory at low densities, while remaining agnostic to any nuclear theory at high densities. To achieve this, we use a nonparametric equation of state model to incorporate the correlations of the underlying relativistic mean-field theory equation of state at low pressures and transition to more flexible correlations above some chosen pressure scale. We perform astrophysical inference under various choices of the transition pressure between the theory-informed and theory-agnostic models. We further study whether the chosen relativistic mean-field theory breaks down above some particular pressure and find no such evidence. Using simulated data for future astrophysical observations at about two-to-three times the precision of current constraints, we show that our method can identify the breakdown pressure associated with a potential strong phase transition
The Meissner Effect and Critical Current Density in Fabricated YBCO Cylindrical Superconductors
No full texthttps://rdc.reed.edu/v1/resources/a3f3a17e-729a-4e34-998b-f682d557f77e/thumb/128.jpgYttrium barium copper oxide (YBCO) high-temperature superconductor samples were prepared at Reed and subjected to a Meissner Effect experiment in order to estimate the maximum sustainable critical current of each sample. The experiment not only provided information on the consistency of the manufacturing method in producing dimensionally similar conductors, but also provided insight into the prevalence of 211 nonsuperconducting inclusions in the samples. Fairly consistent critical current values were found amongst like pellets, with an average of 2.1 · 10^7 A/m^2 with standard deviation of 0.4 · 10^7 A/m^2. These values are comparable in magnitude to those found in similar experiments and may suggest a defect composition of around 14% 211 inclusions, although much further work would need to be performed to confirm the accuracy of this value
ORBITAL DECAY OF HOT JUPITERS DUE TO NONLINEAR TIDAL DISSIPATION WITHIN SOLAR-TYPE HOSTS
No full textWe study the orbital evolution of hot Jupiters due to the excitation and damping of tidally driven g-modes within solar-type host stars. Linearly resonant g-modes (the dynamical tide) are driven to such large amplitudes in the stellar core that they excite a sea of other g-modes through weakly nonlinear interactions. By solving the dynamics of large networks of nonlinearly coupled modes, we show that the nonlinear dissipation rate of the dynamical tide is several orders of magnitude larger than the linear dissipation rate. We find stellar tidal quality factors Q[' over *] ≃ 10[superscript 5]–10[superscript 6] for systems with planet mass M[subscript p] ≳ 0.5M[subscript J] and orbital period P ≲ 2\;\mathrm{days},$ which implies that such systems decay on timescales that are small compared to the main-sequence lifetime of their solar-type hosts. According to our results, there are ≃ 10 currently known exoplanetary systems, including WASP-19b and HAT-P-36-b, with orbital decay timescales shorter than a Gyr. Rapid, tidally induced orbital decay may explain the observed paucity of planets with M[subscript p] ≳ M[subscript J] and P < 2 days around solar-type hosts and could generate detectable transit-timing variations in the near future.National Science Foundation (U.S.) (Laser Interferometer Gravitational-Wave Observatory PHY-0757058)United States. National Aeronautics and Space Administration (NNX14AB40G
Tidal Dissipation in WASP-12
No full textWASP-12 is a hot Jupiter system with an orbital period of P = 1.1 days, making it one of the shortest-period giant planets known. Recent transit timing observations by Maciejewski et al. and Patra et al. found a decreasing period with = 3.2 Myr. This has been interpreted as evidence of either orbital decay due to tidal dissipation or a long-term oscillation of the apparent period due to apsidal precession. Here, we consider the possibility that it is orbital decay. We show that the parameters of the host star are consistent with either a M ∗ ≃ 1.3 M o main sequence star or a M ∗ ≃ 1.2 M o subgiant. We find that if the star is on the main sequence, the tidal dissipation is too inefficient to explain the observed . However, if it is a subgiant, the tidal dissipation is significantly enhanced due to nonlinear wave-breaking of the dynamical tide near the star's center. The subgiant models have a tidal quality factor and an orbital decay rate that agrees well with the observed . It would also explain why the planet survived for ≃3 Gyr while the star was on the main sequence and yet is now inspiraling on a 3 Myr timescale. Although this suggests that we are witnessing the last ∼0.1% of the planet's life, the probability of such a detection is a few percent given the observed sample of ≃30 hot Jupiters in P 1.2 M o hosts
Frequency-dependent responses in third generation gravitational-wave detectors
No full textInterferometric gravitational-wave detectors are dynamic instruments. Changing gravitational-wave strains influence the trajectories of null geodesics and therefore modify the interferometric response. These effects will be important when the associated frequencies are comparable to the round-trip light travel time down the detector arms. The arms of advanced detectors currently in operation are short enough that the strain can be approximated as static, but planned 3rd generation detectors, with arms an order of magnitude longer, will need to account for these effects. We investigate the impact of neglecting the frequency-dependent detector response for compact binary coalescences and show that it can introduce large systematic biases in localization, larger than the statistical uncertainty for 1.4-1.4 M[subscript ⊙] neutron star coalescences at z ≲ 1.7. Analysis of 3rd generation detectors therefore must account for these effects
Impact of the PSR J0740+6620 radius constraint on the properties of high-density matter: Selected quantiles of microscopic and macroscopic variables from NSEOS inference
No full textWe provide data needed to reproduce the main content of figures 1, 2, and 6 in our paper Impact of the PSR J0740+6620 radius constraint on the properties of high-density matter. Quantiles.zip inflates to Quantiles, a directory housing data, a README.md, and an example python script (plot_quantiles.py) giving examples of plotting the data stored in the quantiles CSV files. See the README.md, for more information. The data is stored in CSV files in the `Quantiles` subdirectory which holds quantile information for variables at selected values of another underlying variable. These quantiles are determined by distributions on the nuclear equation of state, computed from priors given by nonparametric gaussian-process regression techniques of Landry and Essick(2019), and likelihoods based on astrophysical observables (see Landry, Essick, and Chatziioannou 2020). The quantiles represent a property of the distribution on EoSs, and are not the posterior distribution themselves, see the note below. Nevertheless, these quantiles can be used to construct symmetric credible intervals for quantities of interest. For example, the pressure-baryon density quantiles could be used to construct a symmetric credible interval for the pressure of nuclear matter at nuclear saturation density, an important quantity in nuclear physics.Note: These data do not provide direct constraints on EoS candidates. In particular, a candidate EoS is not necessarily ruled out at 90% credibility if it deviates from the 90% credible region. The python executable is optimized for python3, all dependent packages are publicly available through pip (and most likely through conda)
LOCALIZATION OF SHORT DURATION GRAVITATIONAL-WAVE TRANSIENTS WITH THE EARLY ADVANCED LIGO AND VIRGO DETECTORS
No full textThe Laser Interferometer Gravitational wave Observatory (LIGO) and Virgo advanced ground-based gravitational-wave detectors will begin collecting science data in 2015. With first detections expected to follow, it is important to quantify how well generic gravitational-wave transients can be localized on the sky. This is crucial for correctly identifying electromagnetic counterparts as well as understanding gravitational-wave physics and source populations. We present a study of sky localization capabilities for two search and parameter estimation algorithms: coherent WaveBurst, a constrained likelihood algorithm operating in close to real-time, and LALInferenceBurst, a Markov chain Monte Carlo parameter estimation algorithm developed to recover generic transient signals with latency of a few hours. Furthermore, we focus on the first few years of the advanced detector era, when we expect to only have two (2015) and later three (2016) operational detectors, all below design sensitivity. These detector configurations can produce significantly different sky localizations, which we quantify in detail. We observe a clear improvement in localization of the average detected signal when progressing from two-detector to three-detector networks, as expected. Although localization depends on the waveform morphology, approximately 50% of detected signals would be imaged after observing 100-200 deg2 in 2015 and 60-110 deg2 in 2016, although knowledge of the waveform can reduce this to as little as 22 deg2. This is the first comprehensive study on sky localization capabilities for generic transients of the early network of advanced LIGO and Virgo detectors, including the early LIGO-only two-detector configuration.National Science Foundation (U.S.) (PHY-1205512)National Science Foundation (U.S.) (PHY-0855313)National Science Foundation (U.S.) (NSF cooperative agreement PHY-0757058
Detectability of dynamical tidal effects and the detection of gravitational-wave transients with LIGO
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 186-201).Dynamical tidal effects impact the orbital motion of extended bodies, imprinting themselves in several measurable ways. This thesis explores the saturation of weakly nonlinear dynamical tidal interactions within two very different systems: hot Jupiters orbiting main-sequence hosts with radiative cores and compact stellar remnants inspiraling due to gravitational radiation. In addition, it discusses general aspects of detecting Gravitational Waves with ground-based laser interferometers. Data quality and noise reduction along with source parameter estimation, with particular emphasis on localization, are discussed in great detail. Conclusions drawn from statistical ensembles of simulated signals are applied to the first three confirmed detections of Gravitational Waves, all from the coalescence of binary black hole systems.by Reed Clasey Essick.Ph. D
Impact of the tidal p−g instability on the gravitational wave signal from coalescing binary neutron stars
No full textRecent studies suggest that coalescing neutron stars are subject to a fluid instability involving the nonlinear coupling of the tide to p modes and g modes. Its influence on the inspiral dynamics and thus the gravitational wave signal is, however, uncertain because we do not know precisely how the instability saturates. Here we construct a simple, physically motivated model of the saturation that allows us to explore the instability’s impact as a function of the model parameters. We find that for plausible assumptions about the saturation, current gravitational wave detectors might miss >70% of events if only point particle waveforms are used. Parameters such as the chirp mass, component masses, and luminosity distance might also be significantly biased. On the other hand, we find that relatively simple modifications to the point particle waveform can alleviate these problems and enhance the science that emerges from the detection of binary neutron stars.United States. National Aeronautics and Space Administration (ATP Grant NNX14AB40G)National Science Foundation (U.S.)Laser Interferometer Gravitational Wave Observator
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