Recursos de colección
Caltech Authors (144.724 recursos)
Repository of works by Caltech published authors.
Status = Unpublished
Repository of works by Caltech published authors.
Status = Unpublished
A second mylar head is easily fashioned into a horizontal annular flange, inspired by the Bacon and Dobson tone rings. Its effect is dramatic, suppressing the “ping” associated with the attack sound of metal picks on metal strings on taut mylar heads but leaving most other features unscathed. The flange itself takes only minutes to make. An old or previously torn head can be used. It is installed directly under the regular head, without any further modifications, and, so, can be removed with no harm done.
Carroll, Sean M.; Remmen, Grant N.
We construct a model in which the cosmological constant is canceled from the gravitational equations of motion. Our model relies on two key ingredients: a nonlocal constraint on the action, which forces the spacetime average of the Lagrangian density to vanish, and a dynamical way for this condition to be satisfied classically with arbitrary matter content. We implement the former condition with a spatially-constant Lagrange multiplier associated with the volume form and the latter by including a free four-form gauge field strength in the action. These two features are enough to remove the cosmological constant from the Einstein equation. The model is consistent with all cosmological and experimental bounds...
Luxemburg, W. A. J.
The present lecture notes have grown from a series of three lectures which were given by the author at the California Institute of Technology in December 1961. The purpose of these lectures was to give a discussion of A. Robinson's theory of infinitesimals and infinitely large numbers which had just appeared in print under the title "Non-Standard Analysis". The title "Non-Standard Analysis" refers to the fact that this theory is an interpretation of analysis in a non-standard model of the arithmetic of the real numbers.
Luxemburg, W. A. J.
Course description from Caltech Catalog (1960/61): Ma 108 abc. Advanced Calculus. 12 units (4-0-8); three terms. Prerequisite: Ma 2. In this course, a sequel to Ma 2, more advanced techniques and applications of calculus are treated. Point set topology is the point of departure for the theory of convergence, and applications are made to implicit functions, partial differentiation, infinite series and infinite products of real and complex numbers. Other topics treated include: uniform convergence of sequences of functions; functions defined by integrals; Fourier series and integrals; analytic functions of a complex variable.
McCoy, Michael B.; Tropp, Joel A.
Demixing is the problem of identifying multiple structured signals from a superimposed, undersampled, and noisy observation. This work analyzes a general framework, based on convex optimization, for solving demixing problems. When the constituent signals follow a generic incoherence model, this analysis leads to precise recovery guarantees. These results admit an attractive interpretation: each signal possesses an intrinsic degrees-of-freedom parameter, and demixing can succeed if and only if the dimension of the observation exceeds the total degrees of freedom present in the observation.
Singh, S.; De Lorenzo, L. A.; Pikovsky, I.; Schwab, K. C.
Direct detection of gravitational waves is opening a new window onto our universe. Here, we study the sensitivity to continuous-wave strain fields of a kg-scale optomechanical system formed by the acoustic motion of super fluid helium-4 parametrically coupled to a superconducting microwave cavity. This narrowband detection scheme can operate at very high Q-factors, while the resonant frequency is tunable through pressurization of the helium in the 0.1-1.5 kHz range. The detector can therefore be tuned to a variety of astrophysical sources and can remain sensitive to a particular source over a long period of time. For reasonable experimental parameters, we...
Ruderman, H.; Gomez, R.; Tollestrup, A. V.
Two identical large lead glass shower detectors, or Cerenkov counters, have been built to detect and measure the energies of decay photons from neutral pions. This method of detecting high energy gamma rays has the advantage of 100 percent efficiency, good energy resolution, linearity of response, insensitivity to heavy charged particles, and short time resolution. In addition, the physical size of the detector need only increase logarithmically with the energy of the incident particle to preserve linearity and resolution.
Bray, Nicolas L.; Pimentel, Harold; Melsted, Páll; Pachter, Lior
We present a novel approach to RNA-Seq quantification that is near optimal in speed and accuracy. Software implementing the approach, called kallisto, can be used to analyze 30 million unaligned paired-end RNA-Seq reads in less than 5 minutes on a standard laptop computer while providing results as accurate as those of the best existing tools. This removes a major computational bottleneck in RNA-Seq analysis.
Mullins, J. H.
The following is an analytic investigation, using first order theory only, of a proposed achromatic inflector for the Caltech Synchrotron. Nothing new in principle is involved in any of the theory presented below, and similar types of analyses have been carried out by others). The investigation was prompted by the need to find a specific achromatic inflector to couple a 10 MeV electron linac to the Caltech synchrotron. In particular, it was desired to find a system such that the injector was placed in a convenient location, and, if any electrostatic elements were used, that they have reasonably low required...
Watson, Keith R.; Hankins, Denis
Recent theoretical investigations of high energy nucleon-nucleon collisions support the two-center model of multiple meson production as discussed by Ciok, et al. To facilitate a prediction of the most probable distribution of shower particles as a function of laboratory energy, Farley's kinematical treatment of the "two-fireball" model is employed. A statistical determination of the multiplicity of pion (including neutrals) production per collision is assumed to be valid with possible corrections suggested through restrictions imposed by experimental values of the inelasticity, Κ_π.
Glashow, Sheldon L.; Gell-Mann, Murray
The possibility of generalizing the Yang-Mills trick is examined. Thus we seek theories of vector bosons invariant under continuous groups of coordinate-dependent linear transformations. All such theories may be expressed as superpositions of certain "simple" theories; we show that each "simple" theory is associated with a simple Lie algebra. We may introduce mass terms for the vector bosons at the price of destroying the gauge-invariance for coordinate-dependent gauge functions. The theories corresponding to three particular simple Lie algebras — those which admit precisely two commuting quantum num- bers — are examined in some detail as examples. One of them might play...
Evans, A. S.; Scoville, N. Z.; Dinshaw, N.; Armus, L.; Soifer, B. T.; Neugebauer, G.; Rieke, M.
High-resolution, 1.10, 2.05, 2.12, and 2.15 μm imaging of the gravitationally lensed system FSC10214+4724 are presented. These data extend Hubble Space Telescope (HST) observations of the lens system to redder wavelengths, thus providing the highest resolution images to date of the rest-frame optical and narrow-line (i.e., Hɑ+[N II]) regions of the background quasar. The length of the arc in the wide-band continuum images increases with increasing wavelength, and the Hɑ+[N II] emission has a length in between that of the 1.10 and 2.05 μm. The structure of the arc changes from having an eastern and western peak at 1.10 μm to...
In this work I report on the stochastic X-ray variability of the 340 Hz accreting millisecond pulsar MAXI J0911-655. Analyzing pointed observations of the XMM-Newton and NuSTAR observatories I find that the source shows broad band-limited stochastic variability in the $0.01-10$ Hz range, with a total fractional variability of $\sim24\%$ rms in the $0.4-3$ keV energy band, which increases to $\sim40\%$ rms in the $3-10$ keV band. Additionally a pair of harmonically related quasi-periodic oscillations are discovered. The fundamental frequency of this harmonic pair is observed between frequencies of $62$ mHz and $146$ mHz. Like the band-limited noise, the amplitude of the QPOs show a steep increase as a...
Tropp, Joel A.; Yurtsever, Alp; Udell, Madeleine; Cevher, Volkan
This paper develops a suite of algorithms for constructing low-rank approximations of an input matrix from a random linear image of the matrix, called a sketch. These methods can preserve structural properties of the input matrix, such as positive-semidefiniteness, and they can produce approximations with a user-specified rank. The algorithms are simple, accurate, numerically stable, and provably correct. Moreover, each method is accompanied by an informative error bound that allows users to select parameters a priori to achieve a given approximation quality. These claims are supported by computer experiments.
Bahramian, Arash; Heinke, Craig O.; Tudor, Vlad; Miller-Jones, James C. A.; Bogdanov, Slavko; Maccarone, Thomas J.; Knigge, Christian; Sivakoff, Gregory R.; Chomiuk, Laura; Strader, Jay; Garcia, Javier A.; Kallman, Timothy
47 Tuc X9 is a low mass X-ray binary (LMXB) in the globular cluster 47 Tucanae, and was previously thought to be a cataclysmic variable. However, Miller-Jones et al. (2015) recently identified a radio counterpart to X9 (inferring a radio/X-ray luminosity ratio consistent with black hole LMXBs), and suggested that the donor star might be a white dwarf. We report simultaneous observations of X9 performed by Chandra, Nustar and Australia Telescope Compact Array. We find a clear 28.18$\pm$0.02 min periodic modulation in the Chandra data, which we identify as the orbital period, confirming this system as an ultracompact X-ray binary. Our X-ray spectral fitting provides evidence for photoionized gas...
Peterson, Vincent Z.
This report is an examination of the principal characteristics of a vacuum system for the proposed 300 Bev cascade synchrotron 1). In par- ticular, we wish to see whether the small aperture and large circumference of the Main Ring present vacuum difficulties. Gas scattering losses, eddy currents in the vacuum chamber wall, and cost of a 5-mile vacuum system are of special interest. Attention has been directed primarily toward the Main Ring. The 10 Gev Booster Ring 1) has vacuum requirements similar to existing accelerators, and it is presumed that duplication or modification of such vacuum systems will be practical. Our...
Yaron, O.; Perley, D. A.; Gal-Yam, A.; Groh, J. H.; Horesh, A.; Ofek, E. O.; Kulkarni, S. R.; Sollerman, J.; Fransson, C.; Rubin, A.; Szabo, P.; Sapir, N.; Taddia, F.; Cenko, S. B.; Valenti, S.; Arcavi, I.; Howell, D. A.; Kasliwal, M. M.; Vreeswijk, P. M.; Khazov, D.; Fox, O. D.; Cao, Y.; Gnat, O.; Kelly, P. L.; Nugent, P. E.; Filippenko, A. V.; Laher, R. R.; Wozniak, P. R.; Lee, W. H.; Rebbapragada, U. D.; Maguire, K.; Sullivan, M.; Soumagnac, M. T.
With the advent of new wide-field, high-cadence optical transient surveys, our understanding of the diversity of core-collapse supernovae has grown tremendously in the last decade. However, the pre-supernova evolution of massive stars, that sets the physical backdrop to these violent events, is theoretically not well understood and difficult to probe observationally. Here we report the discovery of the supernova iPTF13dqy = SN 2013fs, a mere ~3 hr after explosion. Our rapid follow-up observations, which include multiwavelength photometry and extremely early (beginning at ~6 hr post-explosion) spectra, map the distribution of material in the immediate environment (≾ 10^(15) cm) of the...
Peretsman-Clement, Gail; Wrublewski, Donna
Today's researchers are challenged to master an ever-expanding and interlinked set of information and publishing skills in the rapidly evolving scholarly web. An emerging approach, called carpentry, teaches researchers at all career stages best practices and efficient tools for handling, sharing, publishing, and providing fair attribution for research outputs of all types: data, software, and papers. The ultimate aim of software, data and author carpentry is to support more open, transparent, and reusable research to advance and strengthen science in the digital era. This workshop will introduce you to principles of carpentry, teach you a carpentry module on examining, cleaning,...
Barna, Arpad; Marshall, Howard J.
A distributed amplifier with a stable gain of 10, risetime of 2.5 nanoseconds for 125 ohm load impedance is described. The maximum output voltage is 3.2 volts with negative polarity. The amplifier consists of 2 stages of 6 Philco 2N1742 transistors each and an emitter follower using a 2N1500. Design formulae are derived and detailed performance of a specific amplifier is given.
The purpose of this note is to study the effects on betatron frequencies -- in particular, their variation with particle energy — due to non-linear magnet fields. The idea is to determine whether non- linearities can be introduced deliberately in such a way that ν, the number of betatron wavelengths in the circumference, is independent of particle energy for energies near the equilibrium energy. The result is that non-linearities of a magnitude such that the field index n varies by about 1 per cent per cm will suffice.