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Caltech Authors (108,052 recursos)
Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 2,947

1. The Holographic Entropy Cone - Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael
We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phase space of Ryu-Takayanagi entropies, defining the holographic entropy cone....

2. Science with KRAKENS - Mazin, Benjamin A.; Becker, George; France, Kevin; Fraser, Wesley; Howell, D. Andrew; Jones, Tucker; Meeker, Seth; O'Brien, Kieran; Prochaska, Jason X.; Siana, Brian; Strader, Matthew; Szypryt, Paul; Tendulkar, Shriharsh P.; Treu, Tommaso; Vasisht, Gautam
The Keck science community is entering an era of unprecedented change. Powerful new instrument like ZTF, JWST, LSST, and the ELTs will catalyze this change, and we must be ready to take full advantage to maintain our position of scientific leadership. The best way to do this is to continue the UC and Caltech tradition of technical excellence in instrumentation. In this whitepaper we describe a new instrument called KRAKENS to help meet these challenges. KRAKENS uses a unique detector technology (MKIDs) to enable groundbreaking science across a wide range of astrophysical research topics. This document will lay out the detailed expected science return of KRAKENS.

3. Accurate, Meshless Methods for Magneto-Hydrodynamics - Hopkins, Philip F.; Raives, Matthias J.
Recently, we developed a pair of meshless finite-volume Lagrangian methods for hydrodynamics: the 'meshless finite mass' (MFM) and 'meshless finite volume' (MFV) methods. These capture advantages of both smoothed-particle hydrodynamics (SPH) and adaptive mesh-refinement (AMR) schemes. Here, we extend these to include ideal magneto-hydrodynamics (MHD). The MHD equations are second-order consistent and conservative. We augment these with a divergence-cleaning scheme, which maintains ▼ B~0 to high accuracy. We implement these in the code GIZMO, together with a state-of-the-art implementation of SPH MHD. In every one of a large suite of test problems, the new methods are competitive with moving-mesh and AMR schemes using constrained transport (CT) to ensure ▼B=0. They...

4. Distorted cyclotron line profile in Cep X-4 as observed by NuSTAR - Fürst, F.; Pottschmidt, K.; Miyasaka, H.; Bhalerao, V.; Bachetti, M.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Grinberg, V.; Hailey, C. J.; Harrison, F. A.; Kennea, J. A.; Rahoui, F.; Stern, D.; Tendulkar, S. P.; Tomsick, J. A.; Walton, D. J.; Wilms, J.; Zhang, W. W.
We present spectral analysis of NuSTAR and Swift observations of Cep X-4 during its outburst in 2014. We observed the source once during the peak of the outburst and once during the decay, finding good agreement in the spectral shape between the observations. We describe the continuum using a powerlaw with a Fermi-Dirac cutoff at high energies. Cep X-4 has a very strong cyclotron resonant scattering feature (CRSF) around 30 keV. A simple absorption-like line with a Gaussian optical depth or a pseudo-Lorentzian profile both fail to describe the shape of the CRSF accurately, leaving significant deviations at the red side of the line. We characterize this asymmetry...

5. Light Curves of Core-Collapse Supernovae with Substantial Mass Loss using the New Open-Source SuperNova Explosion Code (SNEC) - Morozova, V.; Piro, A. L.; Renzo, M.; Ott, C. D.; Clausen, D.; Couch, S. M.; Ellis, J.; Roberts, L. F.
We present the SuperNova Explosion Code (SNEC), an open-source Lagrangian code for the hydrodynamics and equilibrium-diffusion radiation transport in the expanding envelopes of supernovae. Given a model of a progenitor star, an explosion energy, and an amount and distribution of radioactive nickel, SNEC generates the bolometric light curve, as well as the light curves in different wavelength bands assuming black body emission. As a first application of SNEC, we consider the explosions of a grid of 15 M_⊙ (at zero-age main sequence) stars whose hydrogen envelopes are stripped to different extents and at different points in their evolution. The resulting light curves exhibit plateaus with durations...

6. Spectroscopic Confirmation of the Dwarf Galaxies Hydra II and Pisces II and the Globular Cluster Laevens 1 - Kirby, Evan N.; Simon, Joshua D.; Cohen, Judith G.
We present Keck/DEIMOS spectroscopy of stars in the recently discovered Milky Way satellites Hydra II, Pisces II, and Laevens 1. We measured a velocity dispersion of 5.4 +3.6/−2.4 km s^(−1) for Pisces II, but we did not resolve the velocity dispersions of Hydra II or Laevens 1. We marginally resolved the metallicity dispersions of Hydra II and Pisces II but not Laevens 1. Furthermore, Hydra II and Pisces II obey the luminosity–metallicity relation for Milky Way dwarf galaxies (h[Fe/H]i = −2.02 ± 0.08 and −2.45 ± 0.07, respectively), whereas Laevens 1 does not (h[Fe/H]i = −1.68 ± 0.05). The kinematic and chemical properties suggest that...

7. Phase-resolved NuSTAR and Swift-XRT Observations of Magnetar 4U 0142+61 - Tendulkar, Shriharsh P.; Hascoët, Romain; Yang, Chengwei; Kaspi, Victoria M.; Beloborodov, Andrei M.; An, Hongjun; Bachetti, Matteo; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Guillot, Sebastien; Hailey, Charles A.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.
We present temporal and spectral analysis of simultaneous 0.5-79 keV Swift-XRT and NuSTAR observations of the magnetar 4U 0142+61. The pulse profile changes significantly with photon energy between 3 and 35 keV. The pulse fraction increases with energy, reaching a value of ~20%, similar to that observed in 1E 1841-045 and much lower than the ~80% pulse fraction observed in 1E 2259+586. We do not detect the 55-ks phase modulation reported in previous Suzaku-HXD observations. The phase-averaged spectrum of 4U 0142+61 above 20 keV is dominated by a hard power law with a photon index, Γ ~ 0.65, and the...

8. Geology of drill hole UE25p#1; a test hole into pre-Tertiary rocks near Yucca Mountain, southern Nevada - Carr, Michael D.; Waddell, Sandra J.; Vick, Greg S.; Stock, Joanne M.; Monsen, Susan A.; Harris, Anita G.; Cork, Byron W.; Byers, Frank M., Jr.
Yucca Mountain in southern Nye County, Nevada, has been proposed as a potential site for the underground disposal of high-level nuclear waste. An exploratory drill hole designated UE25p#1 was drilled 3 km east of the proposed repository site to investigate the geology and hydrology of the rocks that underlie the Tertiary volcanic and sedimentary rock sequence forming Yucca Mountain. Silurian dolomite assigned to the Roberts Mountain and Lone Mountain Formations was intersected below the Tertiary section between a depth of approximately 1244 m (4080 ft) and the bottom of the drill hole at 1807 m (5923 ft). These formations are part of an important regional carbonate aquifer in the...

9. Characterizing Average Properties of Southern California Ground Motion Amplitudes and Envelopes - Cua, Georgia; Heaton, Thomas H.
We examine ground motion envelopes of horizontal and vertical acceleration, velocity, and filtered displacement recorded within 200 km from southern California earthquakes in the magnitude range 2 < M ≤ 7.3. We introduce a parameterization that decomposes the observed ground motion envelope into P-wavetrain, S-wavetrain, and ambient noise envelopes. The shape of the body wave envelopes as a function of time is further parameterized by a rise time, a duration, a constant amplitude, and 2 coda decay parameters. Each observed ground motion envelope can thus be described by 11 envelope parameters. We fit this parameterization to 30,000 observed ground motion...

10. Protein degradation in a TX-TL cell-free expression system using ClpXP protease - Sun, Zachary Z.; Kim, Jongmin; Singhal, Vipul; Murray, Richard M.
An in vitro S30-based Escherichia coli expression system (“Transcription-Translation”, or “TX-TL”) has been developed as an alternative prototyping environment to the cell for synthetic circuits [1-5]. Basic circuit elements, such as switches and cascades, have been shown to function in TX-TL, as well as bacteriophage assembly [2, 6]. Circuits can also be prototyped from basic parts within 8 hours, avoiding cloning and transformation steps [7]. However, most published results have been obtained in a “batch mode” reaction, where factors that play an important role for in vivo circuit dynamics – namely protein degradation and protein dilution – are severely hindered...

11. Cavitation Inception on the I.T.T.C. Standard Head Form - Acosta, A. J.; Hamaguchi, H.
Cavitation inception measurements were made on the I.T.T.C. Standard Head Form over a range of speeds and dissolved air content. The results were similar to those observed in other water tunnels with resorbers. Cavitation inception indices were observed as low as 0. 4 as compared with the minimum calculated pressure coefficient of O.6. As in previous measurements a pronounced velocity scale effect was observed.

12. Linearized Theory of a Two-Dimensional Planing Flat Plate in a Channel of Finite Depth - I - Ai, D. K.; Acosta, A. J.; Harrison, Z. L.
Linearized free-streamline theory is used to calculate the spray-sheet thickness and lift-slope for a flat plate, cavitating, two-dimensional hydrofoil in a channel of finite depth with an upper free surface and lower boundary partly free and partly rigid. Only the case of zero cavitation number is considered. Some measurements were made of the submergence of a hydrofoil of four inches chord beneath the undisturbed free surface at velocities of 12 and 18ft./sec. These agree with the trends of the theory but not with the magnitudes, the submergence always being greater than that predicted by the theory.

13. The Effects of Atmospheric Pressure Upon the Water Entry Behavior of a Missile Having a Hemispherical Nose and Flared-Cone Tail - Wilcox, Genevieve M.
At the request of the Naval Ordnance Test Station, Inyokern, Pasadena Annex, several tests were made at the Hydrodynamics Laboratory, California Institute of Technology, under contract NOrd 9612 to supplement the investigation being made at the Naval Ordnance Test Station (NOTS) under NOTS Task Assignment Re 3d-454-1-52. The NOTS study refers to air-launched missile shapes which oscillate in the cavity during the cavity phase of the underwater trajectory. The purpose of the study is to correlate the behavior of these missiles in terms of distance traveled between the contacts of the tail of the missile with the cavity wall. It is hoped that...

14. A Model Study of the Effect of Jet and Exhaust Flow on Drag of the Torpedo Test Vehicle MK 40 X-1 - Waid, R. L.
Experimental investigations of the effects of jets and exhaust on a model of the TTV Mk 40 X-1 are discussed. Photographs of the model jet and exhaust flow patterns are presented. Model pressure distribution data and afterbody drag coefficients are shown for numerous flow conditions. Many correlations among the observed phenomena are discussed. Several estimates of prototype jet- and exhaust-induced drag forces are presented. The susceptibility of the configuration to cavitation is discussed. Detailed analyses of the model results as they pertain to the prototype external flow phenomena are presented. Possible fields of study are suggested which could lead to improved prototype performance...

15. Water Tunnel Observations on the Flow Past a Plano-Convex Hydrofoil - Wade, R. B.
Experimental results of the performance of a plano-convex hydrofoil under non-cavitating and cavitating conditions are presented. Lift, drag and moment coefficients are given as a function of the cavitation number, together with the behavior of the cavity length. Some unsteady effects occurring under cavitating conditions are also considered. In this region of cavitation the magnitude of the force oscillations together with the fluctuation of the cavity length are presented. The frequency of these oscillations and the general behavior of the cavity are discussed.

16. Preliminary Report on The Effect of Jets on the Drag and Cavitation Characteristics of a Two-Dimensional Body - McGraw, J. T.; Kermeen, R. W.; Jackson, V. G.
The effect of hydrojets on the drag characteristics of a two-dimensional hydrofoil was investigated in the High Speed Water Tunnel. The jets were found to affect drag through changes both in skin friction and pressure distribution, and when cavitating they showed some additional change.

17. Plane Couette Flow at Low Mach Number According to the Kinetic Theory of Gases - Yang, Hsun-Tiao; Lees, Lester
The thirteen-moment approximation developed by H. Grad for solving the Maxwell-Boltzmann equation is applied to the problem of the relative shearing motion between two infinite, parallel flat plates (plane Couette flow). In order to bring out the molecular effects as directly as possible the problem is linearized by requiring that the Mach number is small compared with unity, and that the temperature difference between the two plates is small compared with ambient temperature. According to the linearized Grad equations the shear stress in this case is given by the usual Navier-Stokes relation for all values of the parameter Re/M, in agreement with...

18. Fundamental Studies Relating to Systems Analysis of Solid Propellants - Blatz, P. J.; Knauss, W. G.; Schapery, R. A.; Williams, M. L.
Previous reports of this series have attempted to define some of the important parameters affecting structural integrity of solid propellant rocket grains. Three general areas have been discussed, namely material properties, analytical procedures, and criteria for mechanical failure. This particular report is devoted to failure criteria, including both limiting deformation and fracture. First of all, the characteristic material properties of filled and unfilled elastomers are described, followed by a brief description of current and proposed tests which can be conducted to obtain experimental information relating to these characteristics in such a form that they can be incorporated in structural integrity analyses. In particular, the necessity for...

19. On the Added Mass of a Sphere in a Circular Cylinder Considering Real Fluid Effects - Mellsen, S. B.; Ellis, A. T.; Waugh, J. G.
An experimental method combined with boundary layer theory is given for evaluating the added mass of a sphere moving along the axis of a circular cylinder filled with water or oil. The real fluid effects are separated from ideal fluid effects. The experimental method consists essentially of a magnetic steel sphere propelled from rest by an electromagnetic coil in which the current is accurately controlled so that it only supplies force for a short time interval which is within the laminar flow regime of the fluid. The motion of the sphere as a function of time is recorded on single frame photographs using...

20. Experimental Study of Flow Between Centrifugal Pump Shrouds - Tyson, H. N., Jr.
An experimental investigation of flow between the shrouds of an impeller has shown that gross flow separation can occur for "well designed" shapes. Rotation of the shrouds inhibits separation and if the flow coefficient is sufficiently low it will be completely prevented. For the particular impeller shroud profile studied it was found that the velocity distribution in the inlet regions (near where the impeller inlet edge would be placed) is satisfactorily approximated by potential theory. Potential flow velocity distributions on several families of shroud shapes suitable for impeller or supercharger design are then given for use in design.

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