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rss_1.0 Recursos de colección

Caltech Authors (124,343 recursos)
Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 47,305

1. Minimum-action paths for wave-number selection in nonequilibrium systems - Qiao, Liyan; Zheng, Zhigang; Cross, M. C.
The problem of wave-number selections in nonequilibrium pattern-forming systems in the presence of noise is investigated. The minimum-action method is proposed to study the noise-induced transitions between the different spatiotemporal states by generalizing the traditional theory previously applied in low-dimensional dynamical systems. The scheme is shown as an example in the stabilized Kuramoto-Sivashinsky equation. The present method allows us to conveniently find the unique noise selected state, in contrast to previous work using direct simulations of the stochastic partial differential equation, where the constraints of the simulation only allow a narrow band to be determined.

2. Hyperbolic self-gravity solver for large scale hydrodynamical simulations - Hirai, Ryosuke; Nagakura, Hiroki; Okawa, Hirotada; Fujisawa, Kotaro
A new computationally efficient method has been introduced to treat self-gravity in Eulerian hydrodynamical simulations. It is applied simply by modifying the Poisson equation into an inhomogeneous wave equation. This roughly corresponds to the weak field limit of the Einstein equations in general relativity, and as long as the gravitation propagation speed is taken to be larger than the hydrodynamical characteristic speed, the results agree with solutions for the Poisson equation. The solutions almost perfectly agree if the domain is taken large enough, or appropriate boundary conditions are given. Our new method cannot only significantly reduce the computational time compared...

3. First search for Lorentz and CPT violation in double beta decay with EXO-200 - Albert, J. B.; Vogel, P.
A search for Lorentz- and CPT-violating signals in the double beta decay spectrum of ^(136)Xe has been performed using an exposure of 100  kg⋅yr with the EXO-200 detector. No significant evidence of the spectral modification due to isotropic Lorentz-violation was found, and a two-sided limit of −2.65×10^(−5) GeV < â^((3))_(of) < 7.60×10^(−6) GeV (90% C.L.) is placed on the relevant coefficient within the Standard-Model Extension (SME). This is the first experimental study of the effect of the SME-defined oscillation-free and momentum-independent neutrino coupling operator on the double beta decay process.

4. First measurement of muon-neutrino disappearance in NOvA - Adamson, P.; Backhouse, C.; Bays, K.; Howcroft, C.; Lozier, J.; Michael, D.; Mualem, L.; Newman, H. B.; Patterson, R. B.; Pershey, D.; Trevor, J.
This paper reports the first measurement using the NOvA detectors of ν_μ disappearance in a ν_μ beam. The analysis uses a 14 kton-equivalent exposure of 2.74×10^(20) protons-on-target from the Fermilab NuMI beam. Assuming the normal neutrino mass hierarchy, we measure Δm^2_(32) =(2.52^(+0.20)_(−0.18))×10^(−3) eV^2 and sin^2 θ_(23) in the range 0.38–0.65, both at the 68% confidence level, with two statistically degenerate best-fit points at sin^2 θ_(23) =0.43 and 0.60. Results for the inverted mass hierarchy are also presented.

5. Griffiths effects and slow dynamics in nearly many-body localized systems - Gopalakrishnan, Sarang; Agarwal, Kartiek; Demler, Eugene A.; Huse, David A.; Knap, Michael
The low-frequency response of systems near a many-body localization transition can be dominated by rare regions that are locally critical or “in the other phase.” It is known that in one dimension, these rare regions can cause the dc conductivity and diffusion constant to vanish even inside the delocalized thermal phase. Here, we present a general analysis of such Griffiths effects in the thermal phase near the many-body localization transition: we consider both one-dimensional and higher-dimensional systems, subject to quenched randomness, and discuss both linear response (including the frequency- and wave-vector-dependent conductivity) and more general dynamics. In all the regimes...

6. Duality in dynamic discrete-choice models - Chiong, Khai Xiang; Galichon, Alfred; Shum, Matt
Using results from Convex Analysis, we investigate a novel approach to identification and estimation of discrete-choice models that we call the mass transport approach. We show that the conditional choice probabilities and the choice-specific payoffs in these models are related in the sense of conjugate duality, and that the identification problem is a mass transport problem. Based on this, we propose a new two-step estimator for these models; interestingly, the first step of our estimator involves solving a linear program that is identical to the classic assignment (two-sided matching) game of Shapley and Shubik (1971). The application of convex-analytic tools...

7. GW150914: Implications for the Stochastic Gravitational-Wave Background from Binary Black Holes - Abbott, B. P.; Abbott, R.; Abernathy, M. R.; Adhikari, R. X.; Anderson , S. B.; Arai, K.; Araya, M. C.; Barayoga, J. C.; Barish, B. C.; Berger, B. K.; Billingsley, G.; Blackburn, J. K.; Bork, R.; Brooks, A. F.; Cahillane, C.; Callister, T.; Cepeda, C. B.; Chakraborty, R.; Chalermsongsak, T.; Couvares, P.; Coyne, D. C.; Dergachev, V.; Drever, R. W. P.; Ehrens, P.; Etzel, T.; Gossan, S. E.; Gushwa, K. E.; Gustafson, E. K.; Hall, E. D.; Heptonstall, A. W.; Hodge, K. A.; Isi, M.; Kanner, J. B.; Kells, W.; Kondrashov, V.; Korth, W. Z.; Kozak, D. B.; Lazzarini, A.; Li, T. G. F.; Mageswaran, M.; Maros, E.; Martynov, D. V.; Marx, J. N.; McIntyre, G.; McIver, J.; Meshkov, S.; Pedraza, M.; Perreca, A.; Price , L. R.; Quintero, E. A.; Reitze, D. H.; Robertson, N. A.; Rollins, J. G.; Sachdev, S.; Sanchez, E. J.; Schmidt, P.; Shao, Z.; Singer, A.; Smith, N. D.; Smith, R. J. E.; Taylor, R.; Thirugnanasambandam, M. P.; Torrie, C. I.; Vajente, G.; Vass, S.; Wallace, L.; Weinstein, A. J.; Williams, R. D.; Wipf, C. C.; Yamamoto, H.; Zhang, L.; Zucker, M. E.; Zweizig, J.; Chen, Y.; Engels, W.; Thorne, K. S.
The LIGO detection of the gravitational wave transient GW150914, from the inspiral and merger of two black holes with masses ≳30M_⊙, suggests a population of binary black holes with relatively high mass. This observation implies that the stochastic gravitational-wave background from binary black holes, created from the incoherent superposition of all the merging binaries in the Universe, could be higher than previously expected. Using the properties of GW150914, we estimate the energy density of such a background from binary black holes. In the most sensitive part of the Advanced LIGO and Advanced Virgo band for stochastic backgrounds (near 25 Hz),...

8. Time-dependent analysis of B^0 → K^0_Sπ^−π^^+γ decays and studies of the K^+π^−π^+ system in B^+ → K^+π^−π^+γ decays - del Amo Sanchez, P.; Chao, D. S.; Cheng, C. H.; Echenard, B.; Flood, K. T.; Hitlin, D. G.; Kim, J.; Miyashita, T. S.; Ongmongkolkul, P.; Porter, F. C.; Röhrken, M.
We measure the time-dependent CP asymmetry in the radiative-penguin decay B^0→K^0_Sπ^−π^+γ, using a sample of 471×10^6 Υ(4S)→BB¯ events recorded with the BABAR detector at the PEP-II e^+e^− storage ring at SLAC. Using events with mKππ<1.8  GeV/c^2, we measure the branching fractions of B^+→K^+π^−π^+γ and B^0→K^0π^−π^+γ, the branching fractions of the kaonic resonances decaying to K^+π^−π^+, as well as the overall branching fractions of the B^+→ρ^0K^+γ, B^+→K^(*0)π^+γ and S-wave B^+→(Kπ)^(*0)_0π^+γ components. For events from the ρ mass band, we measure the CP-violating parameters SK^0_Sπ^+π^−γ=0.14±0.25±0.03 and CK^0_Sπ^+π^−γ=−0.39±0.20+0.03−0.02, where the first uncertainties are statistical and the second are systematic. We extract from this measurement...

9. Generalized Bloch's theorem for viscous metamaterials: Dispersion and effective properties based on frequencies and wavenumbers that are simultaneously complex - Frazier, Michael J.; Hussein, Mahmoud I.
It is common for dispersion curves of damped periodic materials to be based on real frequencies as a function of complex wavenumbers or, conversely, real wavenumbers as a function of complex frequencies. The former condition corresponds to harmonic wave motion where a driving frequency is prescribed and where attenuation due to dissipation takes place only in space alongside spatial attenuation due to Bragg scattering. The latter condition, on the other hand, relates to free wave motion admitting attenuation due to energy loss only in time while spatial attenuation due to Bragg scattering also takes place. Here, we develop an algorithm...

10. Order, disorder and mixing: The atomic structure of amorphous mixtures of titania and tantala - Bassiri, Riccardo; Abernathy, Matthew R.; Liou, Franklin; Mehta, Apurva; Gustafson, Eric K.; Hart, Martin J.; Isa, Hafizah N.; Kim, Namjun; Lin, Angie C.; MacLaren, Ian; Martin, Iain W.; Route, Roger K.; Rowan, Sheila; Shyam, Badri; Stebbins, Jonathan F.; Fejer, Martin M.
The atomic structure of mixtures of titania (TiO_2) and tantala (Ta_2O_5) ion-beam sputtered amorphous thin film coatings at various post-deposition annealing temperatures have been studied using Ta LIII and Ti K edge Extended X-ray Absorption Fine Structure (EXAFS). The results indicate that post-deposition annealing produces subtle changes in the short range order (< 1 nm) for samples which remain amorphous. We also show that titania–tantala mixtures maintain a structure similar to that of pure tantala, with the titanium atoms preferring to sit at the second shell distance, which is similar to the Ta–Ta distance seen in the pure tantala structure....

11. A Comprehensive Overview Chemical-free Consumer Products - Goldberg, Alexander F. G.; Roth, Klaus; Chemjobber, C. J.
We have examined and subjected to analysis an exhaustive number of consumer products, including but not limited to lotions and cosmetics, herbal supplements, household cleaners, food items, and beverages. As a result we describe all those consumer products herein, to our knowledge, that are appropriately labelled as “Chemical free”.

12. Relics and Writing in Late Medieval England [Book Review] - Jahner, Jennifer
[no abstract]

13. Measurement of angular asymmetries in the decays B → K*ℓ^+ℓ^− - Lees, J. P.; Chao, D. S.; Cheng, C. H.; Echenard, B.; Flood, K. T.; Hitlin, D. G.; Miyashita, T. S.; Ongmongkolkul, P.; Porter, F. C.; Röhrken, M.
We study the lepton forward-backward asymmetry A_(FB) and the longitudinal K* polarization F_L, as well as an observable P_2 derived from them, in the rare decays B→K*ℓ^+ ℓ^−, where ℓ^+ ℓ^− is either e^+e^− or μ^+μ^−, using the full sample of 471 million BB events collected at the Υ(4S) resonance with the BABAR, detector at the PEP-II e^+e^− collider. We separately fit and report results for the K*0(892)ℓ^+ℓ^− and K*^+(892)ℓ^+ℓ^− final states, as well as their combination K*ℓ^+ℓ^−, in five disjoint dilepton mass-squared bins. An angular analysis of B^+ →K*+ℓ^+ ℓ^− decays is presented here for the first time.

14. GW150914: The Advanced LIGO Detectors in the Era of First Discoveries - Abbott, B. P.; Abbott, R.; Abernathy, M. R.; Adhikari, R. X.; Anderson, S. B.; Arai, K.; Araya, M. C.; Barayoga, J. C.; Barish, B. C.; Berger, B. K.; Billingsley, G.; Blackburn, J. K.; Bork, R.; Brooks, A. F.; Cahillane, C.; Callister, T.; Cepeda, C. B.; Chakraborty, R.; Chalermsongsak, T.; Couvares, P.; Coyne, D. C.; Dergachev, V.; Drever, R. W. P.; Ehrens, P.; Etzel, T.; Gossan, S. E.; Gushwa, K. E.; Gustafson, E. K.; Hall, E. D.; Heptonstall, A. W.; Hodge, K. A.; Isi, M.; Kanner, J. B.; Kells, W.; Kondrashov, V.; Korth, W. Z.; Kozak, D. B.; Lazzarini, A.; Li, T. G. F.; Mageswaran, M.; Maros, E.; Martynov, D. V.; Marx, J. N.; McIntyre, G.; McIver, J.; Meshkov, S.; Pedraza, M.; Perreca, A.; Price , L. R.; Quintero, E. A.; Rollins, J. G.; Sachdev, S.; Sanchez, E. J.; Shao, Z.; Singer, A.; Smith, N. D.; Smith, R. J. E.; Taylor, R.; Thirugnanasambandam, M. P.; Torrie, C. I.; Vajente, G.; Vass, S.; Wallace, L.; Weinstein, A. J.; Whitcomb, S. E.; Williams, R. D.; Wipf, C. C.; Yamamoto, H.; Zhang, L.; Zweizig, J.
Following a major upgrade, the two advanced detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) held their first observation run between September 2015 and January 2016. With a strain sensitivity of 10^(−23)/√Hz at 100 Hz, the product of observable volume and measurement time exceeded that of all previous runs within the first 16 days of coincident observation. On September 14, 2015, the Advanced LIGO detectors observed a transient gravitational-wave signal determined to be the coalescence of two black holes [B. P. Abbott et al., Phys. Rev. Lett. 116, 061102 (2016)], launching the era of gravitational-wave astronomy. The event, GW150914, was observed...

15. En route to destruction: the evolution in composition of ices in comet D/2012 S1 (ISON) between 1.2 and 0.34 AU from the sun as revealed at infrared wavelengths - DiSanti, M. A.; Bonev, B. P.; Gibb, E. L.; Paganini, L.; Villanueva, G. L.; Mumma, M. J.; Keane, J. V.; Blake, G. A.; Dello Russo, N.; Meech, K. J.; Vervack, R. J., Jr.; McKay, A. J.
We report production rates for H2O and eight trace molecules (CO, C_2H_6, CH_4, CH_3OH, NH_3, H_2CO, HCN, C_2H_2) in the dynamically new, Sun-grazing Comet C/2012 S1 (ISON), using high-resolution spectroscopy at Keck II and the NASA IRTF on 10 pre-perihelion dates encompassing heliocentric distances R_h = 1.21–0.34 AU. Measured water production rates spanned two orders of magnitude, consistent with a long-term heliocentric power law Q(H_2O) ∝ R_h^(-3.1±0.1). Abundance ratios for CO, C_2H_6, and CH_4 with respect to H_2O remained constant with R_h and below their corresponding mean values measured among a dominant sample of Oort Cloud comets. CH_3OH was also...

16. The HerMES submillimetre local and low-redshift luminosity functions - Marchetti, L.; Bock, J.; Cooray, A.; Dowell, C. D.; Nguyen, H. T.; Schulz, B.; Shupe, D. L.; Viero, M.; Xu, C. K.; Zemcov, M.
We used wide-area surveys over 39 deg2 by the HerMES (Herschel Multi-tiered Extragalactic Survey) collaboration, performed with the Herschel Observatory SPIRE multiwavelength camera, to estimate the low-redshift, 0.02 < z < 0.5, monochromatic luminosity functions (LFs) of galaxies at 250, 350 and 500 μm. Within this redshift interval, we detected 7087 sources in five independent sky areas, ∼40 per cent of which have spectroscopic redshifts, while for the remaining objects photometric redshifts were used. The SPIRE LFs in different fields did not show any field-to-field variations beyond the small differences to be expected from cosmic variance. SPIRE flux densities were also...

17. Pressure-Dependent Polymorphism and Band-Gap Tuning of Methylammonium Lead Iodide Perovskite - Jiang, Shaojie; Fang, Yanan; Li, Ruipeng; Xiao, Hai; Crowley, Jason; Wang, Chenyu; White, Timothy J.; Goddard, William A., III; Wang, Zhongwu; Baikie, Tom; Fang, Jiye
We report the pressure-induced crystallographic transitions and optical behavior of MAPbI_3 (MA=methylammonium) using in situ synchrotron X-ray diffraction and laser-excited photoluminescence spectroscopy, supported by density functional theory (DFT) calculations using the hybrid functional B3PW91 with spin-orbit coupling. The tetragonal polymorph determined at ambient pressure transforms to a ReO_3-type cubic phase at 0.3 GPa. Upon continuous compression to 2.7 GPa this cubic polymorph converts into a putative orthorhombic structure. Beyond 4.7 GPa it separates into crystalline and amorphous fractions. During decompression, this phase-mixed material undergoes distinct restoration pathways depending on the peak pressure. In situ pressure photoluminescence investigation suggests a reduction in band gap with increasing...

18. Performance of the NOνA Data Acquisition and Trigger Systems for the full 14 kT Far Detector - Norman, A.; Davies, G. S.; Ding, P. F.; Dukes, E. C.; Duyan, H.; Frank, M. J.; Group, R. C.; Habig, A.; Henderson, W.; Niner, E.; Mina, R.; Moren, A.; Mualem, L.; Oksuzian, Y.; Rebel, B.; Shanahan, P.; Sheshukov, A.; Tamsett, M.; Tomsen, K.; Vinton, L.; Wang, Z.; Zamorano, B.; Zirnstein, J.
The NOvA experiment uses a continuous, free-running, dead-timeless data acquisition system to collect data from the 14 kT far detector. The DAQ system readouts the more than 344,000 detector channels and assembles the information into an raw unfiltered high bandwidth data stream. The NOvA trigger systems operate in parallel to the readout and asynchronously to the primary DAQ readout/event building chain. The data driven triggering systems for NOvA are unique in that they examine long contiguous time windows of the high resolution readout data and enable the detector to be sensitive to a wide range of physics interactions from those...

19. A data summary file structure and analysis tools for neutrino oscillation analysis at the NOνA experiment - Backhouse, C.; Rocco, D.
The NuMI Off-axis Neutrino Experiment (NOvA) is designed to study neutrino oscillations in the NuMI beam at Fermilab. Neutrinos at the Main Injector (NuMI) is currently being upgraded to provide 700 kW for NOvA. A 14 kt Far Detector in Ash River, MN and a functionally identical 0.3 kt Near Detector at Fermilab are positioned 810 km apart in the NuMI beam line. The fine granularity of the NOvA detectors provides a detailed representation of particle trajectories. The data volume associated with such granularity, however, poses problems for analyzing data with ease and speed. NOvA has developed a data summary...

20. Monte Carlo Production Management at CMS - Boudoul, G.; Franzoni, G.; Norkus, A.; Pol, A.; Srimanobhas, P.; Vlimant, J.-R.
The analysis of the LHC data at the Compact Muon Solenoid (CMS) experiment requires the production of a large number of simulated events. During the RunI of LHC (20102012), CMS has produced over 12 Billion simulated events, organized in approximately sixty different campaigns each emulating specific detector conditions and LHC running conditions (pile up). In order to aggregate the information needed for the configuration and prioritization of the events production, assure the book-keeping of all the processing requests placed by the physics analysis groups, and to interface with the CMS production infrastructure, the web- based service Monte Carlo Management (McM)...

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