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rss_1.0 Recursos de colección

Caltech Authors (80.503 recursos)
Repository of works by Caltech published authors.

Type = Report or Paper

Mostrando recursos 1 - 20 de 2.251

1. Investigation of the Young’s modulus and thermal expansion of amorphous titania-doped tantala films - Abernathy, Matthew R.; Hough, James; Martin, Iain W.; Rowan, Sheila; Oyen, Michelle; Linn, Courtney; Faller, James E.
The current generation of advanced gravitational wave detectors utilize titania-doped tantala/silica multilayer stacks for their mirror coatings. The properties of the low-refractive-index silica are well known; however, in the absence of detailed direct measurements, the material parameters of Young’s modulus and coefficient of thermal expansion (CTE) of the high refractive index material, titania-doped tantala, have been assumed to be equal to values measured for pure tantala coatings. In order to ascertain the true values necessary for thermal noise calculations, we have undertaken measurements of Young’s modulus and CTE through the use of nanoindentation and thermal-bending measurements. The measurements were designed...

2. Inflationary Freedom and Cosmological Neutrino Constraints - de Putter, Roland; Linder, Eric V.; Mishra, Abhilash
The most stringent bounds on the absolute neutrino mass scale come from cosmological data. These bounds are made possible because massive relic neutrinos affect the expansion history of the universe and lead to a suppression of matter clustering on scales smaller than the associated free streaming length. However, the resulting effect on cosmological perturbations is relative to the primordial power spectrum of density perturbations from inflation, so freedom in the primordial power spectrum affects neutrino mass constraints. Using measurements of the cosmic microwave background, the galaxy power spectrum and the Hubble constant, we constrain neutrino mass and number of species for a...

3. 25 Years Ago: The First Asynchronous Microprocessor - Martin, Alain J.
Twenty-five years ago, in December 1988, my research group at Caltech submitted the world’s first asynchronous (“clockless”) microprocessor design for fabrication to MOSIS. We received the chips in early 1989; testing started in February 1989. The chips were found fully functional on first silicon. The results were presented at the Decennial Caltech VLSI Conference in March of the same year. The first entirely asynchronous microprocessor had been designed and successfully fabricated. As the technology finally reaches industry, and with the benefit of a quarter-century hindsight, here is a recollection of this landmark project.

4. An area law and sub-exponential algorithm for 1D systems - Arad, Itai; Kitaev, Alexei; Landau, Zeph; Vazirani, Umesh
We give a new proof for the area law for general 1D gapped systems, which exponentially improves Hastings' famous result [1]. Specifically, we show that for a chain of d-dimensional spins, governed by a 1D local Hamiltonian with a spectral gap ε > 0, the entanglement entropy of the ground state with respect to any cut in the chain is upper bounded by O(log^3 d/ε ). Our approach uses the framework of Refs. [2, 3] to construct a Chebyshev-based AGSP (Approximate Ground Space Projection) with favorable factors. However, our construction uses the Hamiltonian directly, instead of using the Detectability lemma,...

5. An MQ/Code Cyptosystem Proposal - Schulman, Leonard J.
We describe a new trap-door (and PKC) proposal. The proposal is ``multivariate quadratic'' (relies on the hardness of solving systems of quadratic equations); it is also code-based, and uses the code-scrambling technique of McEliece (1978). However, in the new proposal, the error-correcting code is not revealed in the public key, which protects against the leading attacks on McEliece's method.

6. The Capacity of String-Replication Systems - Farnoud (Hassanzadeh), Farzad; Schwartz, Moshe; Bruck, Jehoshua
It is known that the majority of the human genome consists of repeated sequences. Furthermore, it is believed that a significant part of the rest of the genome also originated from repeated sequences and has mutated to its current form. In this paper, we investigate the possibility of constructing an exponentially large number of sequences from a short initial sequence and simple replication rules, including those resembling genomic replication processes. In other words, our goal is to find out the capacity, or the expressive power, of these string-replication systems. Our results include exact capacities, and bounds on the capacities, of four fundamental string-replication...

7. Rate-Distortion for Ranking with Incomplete Information - Farnoud (Hassanzadeh), Farzad; Schwartz, Moshe; Bruck, Jehoshua
We study the rate-distortion relationship in the set of permutations endowed with the Kendall t-metric and the Chebyshev metric. Our study is motivated by the application of permutation rate-distortion to the average-case and worst-case analysis of algorithms for ranking with incomplete information and approximate sorting algorithms. For the Kendall t-metric we provide bounds for small, medium, and large distortion regimes, while for the Chebyshev metric we present bounds that are valid for all distortions and are especially accurate for small distortions. In addition, for the Chebyshev metric, we provide a construction for covering codes.

8. 8D Likelihood Effective Higgs Couplings Extraction Framework in the Golden Channel - Chen, Yi; Di Marco, Emanuele; Spiropulu, Maria; Xie, Si; Lykken, Joe; Vega-Morales, Roberto
In this paper we build a comprehensive analysis framework to perform direct extraction of all possible effective Higgs couplings to neutral electroweak gauge bosons in the decay to electrons and muons, the so called 'golden channel'. Our framework is based on a maximum likelihood method constructed from analytic expressions of the fully differential cross sections for h → 4ℓ and for the dominant irreducible qq → 4ℓ background, where 4ℓ = 2e2µ,4e,4µ. Detector effects are included by an explicit convolution of these analytic expressions with the appropriate transfer function over all center of mass variables. Using the full set of...

9. Scale Effects on Cavitation Inception in Submerged Jets - Ooi, Kean Khoon
The present work is an investigation into the scale effects on cavitation inception in submerged water jets. Four scale effects were studied: (i) jet size, (ii) jet velocity, (iii) dissolved air content, and (iv) the nuclei population in the flow. The nuclei population was artificially altered by "electrolysis seeding." Holography and schlieren photography were used to observe the flow. Direct measurements of the nuclei population were also accomplished by holography. In addition, the instantaneous pressure field in the jet was successfully mapped out using specially tailored bubbles as pressure sensors. It was found that inception did not generally occur in the cores of the turbulent eddies and that the region...

10. Experimental Investigation of Roto-Stator Interaction in Diffuser Pumps - Arndt, Norbert Karl Erhard
The interaction between impeller blades and diffuser vanes in diffuser pumps was investigated. Steady and unsteady pressure measurements were made on the diffuser vanes and on the front shroud wall of a vaned and a vaneless diffuser. Two different impellers were used, one half of the impeller of the double suction pump of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine), and a two-dimensional impeller. The measurements were made for different flow coefficients, shaft speeds, and radial gaps between the impeller blades and the diffuser vanes (1.5% and 4.5% of the impeller discharge radius for the impeller of the HPOTP, and 5% and...

11. Experimental Investigation of the Hydrodynamic Forces on the Shroud of a Centrifugal Pump Impeller - Zhuang, Fei
Fluid-induced forces acting on a rotating impeller are known to cause rotor-dynamic problems in turbomachines. The forces generated by leakage flow along the front shroud surface of a centrifugal turbomachine impeller play an important role among these fluid-induced forces. The present research was aimed to gain a better understanding of these shroud forces. An experimental apparatus was designed and constructed to simulate the impeller shroud leakage flow. Hydrodynamic forces, steady and unsteady pressure distributions on the rotating shroud were measured as functions of eccentricity, width of shroud clearance, face seal clearance and shaft rotating speed. The forces measured from the dynamometer and manometers agreed well. The hydrodynamic force matrices were...

12. Bimodal Distribution of Sulfuric Acid Aerosols in the Upper Haze of Venus - Gao, Peter; Zhang, Xi; Crisp, David; Bardeen, Charles G.; Yung, Yuk L.
Observations by the SPICAV/SOIR instruments aboard Venus Express have revealed that the upper haze (UH) of Venus, between 70 and 90 km, is variable on the order of days and that it is populated by two particle modes. We use a one-dimensional microphysics and vertical transport model based on the Community Aerosol and Radiation Model for Atmospheres to evaluate whether interaction of upwelled cloud particles and sulfuric acid particles nucleated in situ on meteoric dust are able to generate the two observed modes, and whether their observed variability are due in part to the action of vertical transient winds at the...

13. Atom-Light Interactions in Photonic Crystals - Goban, A.; Hung, C.-L.; Yu, S.-P.; Hood, J. D.; Muniz, J. A.; Lee, J. H.; Martin, M. J.; McClung, A. C.; Choi, K. S.; Chang, D. E.; Painter, O.; Kimble, H. J.
The integration of nanophotonics and atomic physics has been a long-sought goal that would open new frontiers for optical physics. Here, we report the development of the first integrated optical circuit with a photonic crystal capable of both localizing and interfacing atoms with guided photons in the device. By aligning the optical bands of a photonic crystal waveguide (PCW) with selected atomic transitions, our platform provides new opportunities for novel quantum transport and many-body phenomena by way of photon-mediated atomic interactions along the PCW. From reflection spectra measured with average atom number N = 1.1 ± 0.4, we infer that...

14. Halo Masses of MgII absorbers at z ~ 0.5 from SDSS DR7 - Gauthier, Jean-René; Chen, Hsiao-Wen; Cooksey, Kathy L.; Simcoe, Robert A.; Seyffert, Eduardo N.; O'Meara, John M.
We present the cross-correlation function of MgII absorbers with respect to a volume-limited sample of luminous red galaxies (LRGs) at z = 0.45 - 0.60 using the largest MgII absorber sample and a new LRG sample from SDSS DR7. We present the clustering signal of absorbers on projected scales r_p = 0.3 - 35 h^(-1) Mpc in four W^(λ2796)_r bins spanning W^(λ2796)_r = 0.4 - 5.6Å. We found that on average Mg II absorbers reside in halos (log M_h) ≈ 12.1, similar to the halo mass of an L_* galaxy. We report that the weakest absorbers in our sample with W^(λ2796)_r...

15. Comment on “A classical model for asymmetric sidebands in cavity optomechanical measurements” - Safavi-Naeini, Amir H.; Painter, Oskar
We respond to a recent manuscript by Tsang [arXiv:1306.2699 ], on whether the measurement presented in Safavi-Naeini et al. [Phys. Rev. Lett. 108, 033 602 (2012)] can be explained “withoutreference to quantum mechanics”. We show that the fully classical analysis provided by Tsang, and previously by Safavi-Naeini et al. [New J. Phys. 15, 035007 (2013)], has been ruled out by our published data. In addition, we discuss the role of the mathematical formulation used on the interpretation of the asymmetry effect, as has previously been considered by Khalili et al. [Phys. Rev. A 86, 033840 (2012)

16. Friends of Hot Jupiters I: A Radial Velocity Search for Massive, Long-Period Companions in Hot Jupiter Systems - Knutson, Heather A.; Fulton, Benjamin J.; Montet, Benjamin T.; Kao, Melodie; Ngo, Henry; Howard, Andrew W.; Crepp, Justin R.; Hinkley, Sasha; Bakos, Gaspar Á.; Batygin, Konstantin; Johnson, John Asher; Morton, Timothy D.; Muirhead, Philip S.
In this paper we search for distant massive companions to known transiting hot Jupiters that may have influenced the dynamical evolution of these systems. We present new radial velocity observations for a sample of 51 hot Jupiters obtained using the Keck HIRES instrument, and use these observations to search for long-term radial velocity accelerations. We find new, statistically significant accelerations in seven systems, including: HAT-P-10, HAT-P-20, HAT-P-22, HAT-P-29, HAT-P-32, WASP-10, and XO-2. We combine our radial velocity fits with Keck NIRC2 AO imaging data to place constraints on the allowed masses and orbital periods of the companions. The estimated masses...

17. Consistent use of Type Ia supernovae highly magnified by galaxy clusters to constrain the cosmological parameters - Zitrin, Adi; Redlich, Matthias; Broadhurst, Tom
We discuss how Type Ia supernovae (SNe) strongly magnified by foreground galaxy clusters should be self-consistently treated when used in samples fitted for the cosmological parameters. While the cluster lens magnification of a SN can be well constrained from sets of multiple images of various background galaxies with measured redshifts, its value is typically dependent on the fiducial set of cosmological parameters used to construct the mass model to begin with. In such cases, one should not naively demagnify the observed SN luminosity by the model magnification into the expected Hubble diagram, which would then create a bias, but take...

18. A multi-wavelength investigation of the radio-loud supernova PTF11qcj and its circumstellar environment - Corsi, A.; Ofek, E. O.; Gal-Yam, A.; Frail, D. A.; Kulkarni, S. R.; Fox, D. B.; Kasliwal, M. M.; Sullivan, M.; Horesh, A.; Carpenter, J.; Maguire, K.; Arcavi, I.; Cenko, S. B.; Cao, Y.; Mooley, K.; Pan, Y.-C.; Sesar, B.; Sternberg, A.; Xu, D.; Bersier, D.; James, P.; Bloom, J. S.; Nugent, P. E.
We present the discovery, classification, and extensive panchromatic (from radio to X-ray) follow-up observations of PTF11qcj, a supernova discovered by the Palomar Transient Factory. PTF11qcj is located at a distance of d_L ≅ 124Mpc. Our observations with the Karl G. Jansky Very Large Array show that this event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to that of the famous gamma-rayburst- associated supernova 1998bw (L_5GHz ≈ 10^(29) erg s^(−1) Hz^(−1)). PTF11qcj is also detected in X-rays with the Chandra observatory, and in the infrared band with Spitzer. Our multi-wavelength analysis probes the supernova interaction with circumstellar material. The radio observations suggest a progenitor mass-loss...

19. SN 2010jl: Optical to hard X-ray observations reveal an explosion embedded in a ten solar mass cocoon - Ofek, Eran O.; Harrison, Fiona A.; Kulkarni, Shrinivas R.; Bellm, Eric; Grefenstette, Brian; Laher, Russ; Madsen, Kristin; Surace, Jason
Some supernovae (SNe) may be powered by the interaction of the SN ejecta with a large amount of circumstellar matter (CSM). However, quantitative estimates of the CSM mass around such SNe are missing when the CSM material is optically thick. Specifically, current estimators are sensitive to uncertainties regarding the CSM density profile and the ejecta velocity. Here we outline a method to measure the mass of the optically thick CSM around such SNe. We present new visible-light and X-ray observations of SN2010jl (PTF 10aaxf), including the first detection of a SN in the hard X-ray band using NuSTAR. The total radiated luminosity of SN2010jl is extreme,...

20. An Early & Comprehensive Millimeter and Centimeter Wave and X-ray Study of Supernova 2011dh: A Non-Equipartition Blastwave Expanding into A Massive Stellar Wind - Horesh, Assaf; Carpenter, John; Kulkarni, S. R.; Ofek, Eran O.; Kasliwal, Mansi M.; Van Dyk, Schuyler D.
Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, starting a few days after explosion. The early detection and classification of the nearby type IIb SN2011dh/PTF11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at the youngest phase ever of a core-collapse supernova (days 3 to 12 after explosion) in the radio, millimeter and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding supernova shockwave does not exhibit...

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