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Articles 91 - 120 of 1329

Full-Text Articles in Physical Sciences and Mathematics

The Interstellar Medium And Feedback In The Progenitors Of The Compact Passive Galaxies At Z ~ 2, Christina C. Williams, Mauro Giavalisco, Bomee Lee, Elena Tundo, Bahram Mobasher, Hooshang Nayyeri, Henry C. Ferguson, Anton Koekemoer, Jonathan R. Trump, Paolo Cassata, Avishai Dekel, Yicheng Guo, Kyoung-Soo Lee, Laura Pentericci, Eric F. Bell, Marco Castellano, Steven L. Finkelstein, Adriano Fontana, Andrea Grazian, Norman Grogin, Dale Kocevski, David C. Koo, Ray A. Lucas, Swara Ravindranath, Paola Santini, Eros Vanzella, Benjamin J. Weiner Jan 2014

The Interstellar Medium And Feedback In The Progenitors Of The Compact Passive Galaxies At Z ~ 2, Christina C. Williams, Mauro Giavalisco, Bomee Lee, Elena Tundo, Bahram Mobasher, Hooshang Nayyeri, Henry C. Ferguson, Anton Koekemoer, Jonathan R. Trump, Paolo Cassata, Avishai Dekel, Yicheng Guo, Kyoung-Soo Lee, Laura Pentericci, Eric F. Bell, Marco Castellano, Steven L. Finkelstein, Adriano Fontana, Andrea Grazian, Norman Grogin, Dale Kocevski, David C. Koo, Ray A. Lucas, Swara Ravindranath, Paola Santini, Eros Vanzella, Benjamin J. Weiner

Mauro Giavalisco

Quenched galaxies at z>2 are nearly all very compact relative to z∼0, suggesting a physical connection between high stellar density and efficient, rapid cessation of star–formation. We present rest–frame UV spectra of Lyman–break galaxies (LBGs) at z ∼ 3 selected to be candidate progenitors of the quenched galaxies at z ∼ 2 based on their compact restframe-optical sizes and high _SFR. We compare their UV properties to those of more extended LBGs of similar mass and star–formation rate (non-candidates). We find that candidate progenitors have faster bulk ISM gas velocities and higher equivalent widths of interstellar absorption lines, implying …

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The Photon Underproduction Crisis, Juna A. Kollmeier, David H. Weinberg, Benjamin D. Oppenheimer, Francesco Haardt, Neal S. Katz, Rameel A. Dave, Mark Fardal, Piero Madau, Charles Danforth, Amanda B. Ford, Molly S. Peeples, Joseph Mcewen Jan 2014

The Photon Underproduction Crisis, Juna A. Kollmeier, David H. Weinberg, Benjamin D. Oppenheimer, Francesco Haardt, Neal S. Katz, Rameel A. Dave, Mark Fardal, Piero Madau, Charles Danforth, Amanda B. Ford, Molly S. Peeples, Joseph Mcewen

Neal S. Katz

We examine the statistics of the low-redshift Lyα forest from smoothed particle hydrodynamic simulations in light of recent improvements in the estimated evolution of the cosmic ultraviolet background (UVB) and recent observations from the Cosmic Origins Spectrograph (COS). We find that the value of the metagalactic photoionization rate (ΓHI) required by our simulations to match the observed properties of the low-redshift Lyα forest is a factor of five larger than the value predicted by state-of-the art models for the evolution of this quantity. This mismatch in ΓHI results in the mean flux decrement of the Lyα forest being overpredicted by …

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Geometry Of Star-Forming Galaxies From Sdss, 3d-Hst And Candels, A. Van Der Wel, Yu-Yen Chang, E. F. Bell, B. P. Holden, H.C. Ferguson, Mauro Giavalisco, H.W. Rix, R. Skelton, K. Whitaker, I. Momcheva, G. Brammer, S.A. Kassin, M. Martig, A. Dekel, D. Ceverino, D.C. Koo, M. Mozena, P.G. Van Dokkum, M. Franx, S.M. Faber, J. Primack Jan 2014

Geometry Of Star-Forming Galaxies From Sdss, 3d-Hst And Candels, A. Van Der Wel, Yu-Yen Chang, E. F. Bell, B. P. Holden, H.C. Ferguson, Mauro Giavalisco, H.W. Rix, R. Skelton, K. Whitaker, I. Momcheva, G. Brammer, S.A. Kassin, M. Martig, A. Dekel, D. Ceverino, D.C. Koo, M. Mozena, P.G. Van Dokkum, M. Franx, S.M. Faber, J. Primack

Mauro Giavalisco

No abstract provided.

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The Cos-Halos Survey: Physical Conditions And Baryonic Mass In The Low-Redshift Circumgalactic Medium, Jessica K. Werk, J. Xavier Prochaska, Jason Tumlinson, Molly S. Peeples, Todd M. Tripp, Andrew J. Fox, Nicolas Lehner, Christopher Thom, John M. O'Meara, Amanda Brady Ford, Rongmon Bordoloi, Neal S. Katz, Nicolas Tejos, Benjamin D. Oppenheimer, Romeel Dave, David H. Weinberg Jan 2014

The Cos-Halos Survey: Physical Conditions And Baryonic Mass In The Low-Redshift Circumgalactic Medium, Jessica K. Werk, J. Xavier Prochaska, Jason Tumlinson, Molly S. Peeples, Todd M. Tripp, Andrew J. Fox, Nicolas Lehner, Christopher Thom, John M. O'Meara, Amanda Brady Ford, Rongmon Bordoloi, Neal S. Katz, Nicolas Tejos, Benjamin D. Oppenheimer, Romeel Dave, David H. Weinberg

Neal S. Katz

We analyze the physical conditions of the cool, photoionized (T ~104 K) circumgalactic medium (CGM) using the COS-Halos suite of gas column density measurements for 44 gaseous halos within 160 kpc of L ~ L* galaxies at z ~ 0.2. These data are well described by simple photoionization models, with the gas highly ionized (n H II /n H gsim 99%) by the extragalactic ultraviolet background. Scaling by estimates for the virial radius, R vir, we show that the ionization state (tracked by the dimensionless ionization parameter, U) increases with distance from the host galaxy. The ionization parameters imply a …

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Ysovar: Mid-Ir Variability In The Star Forming Region Lynds 1688, H. M. Gunther, A. M. Cody, K. R. Covey, L. A. Hillenbrand, P. Plavchan, K. Poppenhaeger, L. M. Rebull, J. R. Stauffer, S. J. Wolk, L. Allen, A. Bayo, R. A. Gutermuth, J. L. Hora, H.Y.A. Meng, M. Morales-Calderon, J. R. Parks, Inseok Song Jan 2014

Ysovar: Mid-Ir Variability In The Star Forming Region Lynds 1688, H. M. Gunther, A. M. Cody, K. R. Covey, L. A. Hillenbrand, P. Plavchan, K. Poppenhaeger, L. M. Rebull, J. R. Stauffer, S. J. Wolk, L. Allen, A. Bayo, R. A. Gutermuth, J. L. Hora, H.Y.A. Meng, M. Morales-Calderon, J. R. Parks, Inseok Song

Robert A. Gutermuth

The emission from young stellar objects (YSOs) in the mid-infrared (mid-IR) is dominated by the inner rim of their circumstellar disks. We present IR data from the Young Stellar Object VARiability (YSOVAR) survey of ~800 objects in the direction of the Lynds 1688 (L1688) star-forming region over four visibility windows spanning 1.6 yr using the Spitzer Space Telescope in its warm mission phase. Among all light curves, 57 sources are cluster members identified based on their spectral energy distribution and X-ray emission. Almost all cluster members show significant variability. The amplitude of the variability is larger in more embedded YSOs. …

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The Vimos Ultra-Deep Survey (Vuds): ~10,000 Galaxies With Spectroscopic Redshifts To Study Galaxy Assembly At Early Epochs 2 < Z ≈ 6, O. Le Fevre, L.A.M. Tasca, P. Cassata, B. Garilli, V. Le Brun, D. Maccagni, L. Pentericci, R. Thomas, E. Vanzella, G. Zamorani, E. Zucca, R. Amorin, S. Bardelli, P. Capak, L. Cassara, M. Castellano, A. Cimatti, J.G. Cuby, O. Cucciati, S. De La Torre, A Durkalec, A. Fontana, Mauro Giavalisco, A. Grazian, N.P. Hathi, O. Ilbert, B.C. Lemaux, C. Moreau, S. Paltani, B. Ribeiro, M. Salvato, D. Schaerer, M. Scodeggio, V. Sommariva, M. Talia, Y. Taniguchi, L. Tresse, D. Vergani, P.W. Wang, S. Charlot, T. Contini, S. Fotopoulou, C. Lopez-Sanjuan, Y. Mellier, N. Scoville Jan 2014

The Vimos Ultra-Deep Survey (Vuds): ~10,000 Galaxies With Spectroscopic Redshifts To Study Galaxy Assembly At Early Epochs 2 < Z ≈ 6, O. Le Fevre, L.A.M. Tasca, P. Cassata, B. Garilli, V. Le Brun, D. Maccagni, L. Pentericci, R. Thomas, E. Vanzella, G. Zamorani, E. Zucca, R. Amorin, S. Bardelli, P. Capak, L. Cassara, M. Castellano, A. Cimatti, J.G. Cuby, O. Cucciati, S. De La Torre, A Durkalec, A. Fontana, Mauro Giavalisco, A. Grazian, N.P. Hathi, O. Ilbert, B.C. Lemaux, C. Moreau, S. Paltani, B. Ribeiro, M. Salvato, D. Schaerer, M. Scodeggio, V. Sommariva, M. Talia, Y. Taniguchi, L. Tresse, D. Vergani, P.W. Wang, S. Charlot, T. Contini, S. Fotopoulou, C. Lopez-Sanjuan, Y. Mellier, N. Scoville

Mauro Giavalisco

We present the VIMOS Ultra Deep Survey (VUDS), a spectroscopic redshift survey of ~10 000 very faint galaxies to study the main phase of galaxy assembly in 2 < z ≃ 6. The survey covers 1 deg2 in three separate fields: COSMOS, ECDFS, and VVDS-02h, with the selection of targets based on an inclusive combination of photometric redshifts and colour properties. Spectra covering 3650 < λ < 9350 Å are obtained with VIMOS on the ESO-VLT with integration times of 14h. Here we present the survey strategy, target selection, data processing, and the redshift measurement process with an emphasis on the specific methods used to adapt to this high-redshift range. We discuss the spectra quality and redshift reliability and derive a success rate in redshift measurement of 91%, or 74% by limiting the dataset to the most reliable measurements, down to a limiting magnitude iAB = 25. Measurements are performed all the way down to iAB = 27. The mean redshift of the main sample is z ~ 3 and extends over a broad redshift range mainly in 2 < z < 6. At 3 < z < 5, the galaxies cover a wide range of luminosities −23 < MNUV < −20.5, stellar mass 109M⊙ < M∗ < 1011M⊙, and star formation rates 1M⊙/yr < SFR < 103M⊙/yr. We discuss the spectral properties of galaxies using individual as well asstacked spectra. The comparison between spectroscopic and photometric redshifts as well as colour selection demonstrate the effectiveness of our selection scheme. From about ~ 90% of the data analysed so far, we expect to assemble >6000 galaxies with reliable spectroscopic redshifts in 2 < z < 6 when complete. This makes the VUDS the largest survey at these redshifts and offers the opportunity for unprecedented studies of the star-forming galaxy population and its distribution in large-scale structures during the main phase of galaxy assembly.

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The Cos-Dwarfs Survey: The Carbon Reservoir Around Sub-L Galaxies, Rongmon Bordoloi, Jason Tumlinson, Jessica K. Werk, Benjamin D. Oppenheimer, Molly S. Peeples, J. Xavier Prochaska, Todd M. Tripp, Neal S. Katz, Romeel Dave, Andrew J. Fox, Christopher Thom, Amanda Brady Ford, David H. Weinberg, Joseph N. Burchett, Juna A. Kollmeier Jan 2014

The Cos-Dwarfs Survey: The Carbon Reservoir Around Sub-L Galaxies, Rongmon Bordoloi, Jason Tumlinson, Jessica K. Werk, Benjamin D. Oppenheimer, Molly S. Peeples, J. Xavier Prochaska, Todd M. Tripp, Neal S. Katz, Romeel Dave, Andrew J. Fox, Christopher Thom, Amanda Brady Ford, David H. Weinberg, Joseph N. Burchett, Juna A. Kollmeier

Neal S. Katz

We report new observations of circumgalactic gas from the COS-Dwarfs survey, a systematic investigation of the gaseous halos around 43 low-mass z ≤ 0.1 galaxies using background QSOs observed with the Cosmic Origins Spectrograph. From the projected one-dimensional and two-dimensional distribution of C iv absorption, we find that C iv is detected out to ≈100 kpc (corresponding roughly to ≈0.5 Rvir) of the host galaxies. The C iv absorption strength falls off radially as a power law, and beyond ≈0.5 Rvir, no C iv absorption is detected above our sensitivity limit of ≈50–100 mÅ. We find a tentative correlation between …

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Connecting X-Ray And Infrared Variability Among Young Stellar Objects: Ruling Out Potential Sources Of Disk Fluctuations, K.M. Flaherty, J. Muzerolle, S.J. Wolk, G. Rieke, R. A. Gutermuth, Z. Balog, W. Herbst, S.T. Mageath, E. Furlan Jan 2014

Connecting X-Ray And Infrared Variability Among Young Stellar Objects: Ruling Out Potential Sources Of Disk Fluctuations, K.M. Flaherty, J. Muzerolle, S.J. Wolk, G. Rieke, R. A. Gutermuth, Z. Balog, W. Herbst, S.T. Mageath, E. Furlan

Robert A. Gutermuth

Variability in the infrared emission from disks around pre-main-sequence stars over the course of days to weeks appears to be common, but the physical cause of the changes in disk structure are not constrained. Here we present coordinated monitoring of one young cluster with the Spitzer and Chandra space telescopes aimed at studying the physical source of the variability. In fall 2011 we obtained 10 epochs of Chandra ACIS photometry over a period of 30 days with a roughly 3 day cadence contemporaneous with 20 epochs of Spitzer [3.6], [4.5] photometry over 40 days with a roughly 2 day cadence …

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Stellar Masses From The Candels Survey: The Goods-South And Uds Field, P. Satini, H.C. Ferguson, A Fontana, B. Mobasher, G. Barro, M. Castellano, S.L. Finkelstein, A. Grazian, L.T. Hsu, B. Lee, S.K. Lee, J. Pforr, M. Salvato, T. Wiklind, S. Wuyts, O. Almaini, M.C. Cooper, A. Galametz, B. Weiner, R. Amorin, K. Boutsia, C.J. Conselice, T. Dahlen, M.C. Cooper, Mauro Giavalisco, N.A. Grogin, Y. Guo, N.P. Hathi, D. Kocevski, A.M. Koekemoer, P. Kurczynski, E. Merlin, A. Mortlock, J.A. Newman, D. Paris, L. Pentericci, R. Simons, S.P. Willner Jan 2014

Stellar Masses From The Candels Survey: The Goods-South And Uds Field, P. Satini, H.C. Ferguson, A Fontana, B. Mobasher, G. Barro, M. Castellano, S.L. Finkelstein, A. Grazian, L.T. Hsu, B. Lee, S.K. Lee, J. Pforr, M. Salvato, T. Wiklind, S. Wuyts, O. Almaini, M.C. Cooper, A. Galametz, B. Weiner, R. Amorin, K. Boutsia, C.J. Conselice, T. Dahlen, M.C. Cooper, Mauro Giavalisco, N.A. Grogin, Y. Guo, N.P. Hathi, D. Kocevski, A.M. Koekemoer, P. Kurczynski, E. Merlin, A. Mortlock, J.A. Newman, D. Paris, L. Pentericci, R. Simons, S.P. Willner

Mauro Giavalisco

We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) project. We combine the effort from ten different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The com- bination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different …

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The Neutral Hydrogen Content Of Galaxies In Cosmological Hydrodynamic Simulations, Romeel Dave, Neal S. Katz, Benjamin D. Oppenheimer, Juna A. Kollmeier, David H. Weinberg Jan 2014

The Neutral Hydrogen Content Of Galaxies In Cosmological Hydrodynamic Simulations, Romeel Dave, Neal S. Katz, Benjamin D. Oppenheimer, Juna A. Kollmeier, David H. Weinberg

Neal S. Katz

We examine the global H I properties of galaxies in quarter billion particle cosmological simulations using GADGET-2, focusing on how galactic outflows impact H I content. We consider four outflow models, including a new one (ezw) motivated by recent interstellar medium simulations in which the wind speed and mass loading factor scale as expected for momentum-driven outflows for larger galaxies and energy-driven outflows for dwarfs (σ < 75 km s−1). To obtain predicted H I masses, we employ a simple but effective local correction for particle self-shielding and an observationally constrained transition from neutral to molecular hydrogen. Our ezw simulation produces an H I mass function whose faint-end slope of −1.3 agrees well with observations from the Arecibo Fast Legacy ALFA survey; other models agree less well. Satellite galaxies have a bimodal distribution in H I fraction versus halo mass, with smaller satellites and/or those in larger haloes more often being H I deficient. At a given stellar mass, H I content correlates with the star formation rate and inversely correlates with metallicity, as expected if driven by stochasticity in the accretion rate. To higher redshifts, massive H I galaxies disappear and the mass function steepens. The global cosmic H I density conspires to remain fairly constant from z ∼ 5 → 0, but the relative contribution from smaller galaxies increases with redshift.

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Honeycomb, Square, And Kagome Vortex Lattices In Superconducting Systems With Multi-Scale Inter-Vortex Interactions, Qingyou Meng, Christopher N. Varney, Hans Fangohr, Egor Babaev Jan 2014

Honeycomb, Square, And Kagome Vortex Lattices In Superconducting Systems With Multi-Scale Inter-Vortex Interactions, Qingyou Meng, Christopher N. Varney, Hans Fangohr, Egor Babaev

Egor Babaev

The recent proposal of Romero-Isart et al. [1] to utilize the vortex lattice phases of superconducting materials to prepare a lattice for ultra-cold atoms-based quantum emulators, raises the need to create and control vortex lattices of different symmetries. Here we propose a mechanism by which honeycomb, hexagonal, square, and kagome vortex lattices could be created in superconducting systems with multi-scale inter-vortex interaction. Multiple scales of the inter-vortex interaction can be created and controlled in layered systems made of different superconducting material or with differing interlayer spacing.

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The Relation Between Star Formation Rate And Stellar Mass For Galaxies At 3.5 < Z < 6.5 In Candels, Brett Salmon, Casey Papovich, Steven L. Finkelstein, Vithal Tilvi, Kristian Flinator, Peter Behroozi, Tomas Dahlen, Romeel Dave, Avishai Dekel, Mark Dickinson, Henry C. Ferguson, Mauro Giavalisco, James Long, Yu Lu, Bahram Mobasher, Naveen Reddy, Rachel S. Somerville, Risa H. Wechsler Jan 2014

The Relation Between Star Formation Rate And Stellar Mass For Galaxies At 3.5 < Z < 6.5 In Candels, Brett Salmon, Casey Papovich, Steven L. Finkelstein, Vithal Tilvi, Kristian Flinator, Peter Behroozi, Tomas Dahlen, Romeel Dave, Avishai Dekel, Mark Dickinson, Henry C. Ferguson, Mauro Giavalisco, James Long, Yu Lu, Bahram Mobasher, Naveen Reddy, Rachel S. Somerville, Risa H. Wechsler

Mauro Giavalisco

No abstract provided.

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Climate Change In The Northeastern Us: Regional Climate Model Validation And Climate Change Projections, Fangxing Fan, Raymond S. Bradley, Michael A. Rawlins Jan 2014

Climate Change In The Northeastern Us: Regional Climate Model Validation And Climate Change Projections, Fangxing Fan, Raymond S. Bradley, Michael A. Rawlins

Raymond S Bradley

A high resolution regional climate model (RCM) is used to simulate climate of the recent past and to project future climate change across the northeastern US. Different types of uncertainties in climate simulations are examined by driving the RCM with different boundary data, applying different emissions scenarios, and running an ensemble of simulations with different initial conditions. Empirical orthogonal functions analysis and K-means clustering analysis are applied to divide the northeastern US region into four climatologically different zones based on the surface air temperature (SAT) and precipitation variability. The RCM simulations tend to overestimate SAT, especially over the northern part …

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Climatic Changes In Mountain Regions Of The American Cordillera And The Tropics: Historical Changes And Future Outlook, Henry F. Diaz, Raymond S. Bradley, Liang Ning Jan 2014

Climatic Changes In Mountain Regions Of The American Cordillera And The Tropics: Historical Changes And Future Outlook, Henry F. Diaz, Raymond S. Bradley, Liang Ning

Raymond S Bradley

We review some recent work regarding climatic changes in selected mountain regions, with particular attention to the tropics and the American Cordillera. Key aspects of climatic variability and trends in these regions are the amplification of surface warming trends with height, and the strong modulation of tempera¬ture trends by tropical sea surface temperature, largely controlled by changes in El Niño–Southern Oscillation on multiple time scales. Corollary aspects of these climate trends include the increase in a critical plant growth temperature threshold, a rise in the freezing level surface, and the possibility of enhanced subtropical drying. Anthropogenic global warming projections indicate …

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Winter Precipitation Variability And Corresponding Teleconnections Over The Northeastern United States, Liang Ning, Raymond S. Bradley Jan 2014

Winter Precipitation Variability And Corresponding Teleconnections Over The Northeastern United States, Liang Ning, Raymond S. Bradley

Raymond S Bradley

The variability of winter precipitation over the northeastern United States and the corresponding teleconnections with five dominant large-scale modes of climate variability (Atlantic Multidecadal Oscillation, AMO; North Atlantic Oscillation, NAO; Pacific-North American pattern, PNA; Pacific Decadal Oscillation, PDO; and El Niño–Southern Oscillation, ENSO) were systemically analyzed in this study. Three leading patterns of winter precipitation were first generated by empirical orthogonal function (EOF) analysis. The correlation analysis shows that the first pattern is significantly correlated with PNA and PDO, the second pattern is significantly correlated with NAO and AMO, and the third pattern is significantly correlated with ENSO, PNA, and …

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Parallelization, Processor Communication And Error Analysis In Lattice Kinetic Monte Carlo, Giorgos Arampatzis, Markos Katsoulakis, Petr Plechac Jan 2014

Parallelization, Processor Communication And Error Analysis In Lattice Kinetic Monte Carlo, Giorgos Arampatzis, Markos Katsoulakis, Petr Plechac

Markos Katsoulakis

In this paper we study from a numerical analysis perspective the fractional step kinetic Monte Carlo (FS-KMC) algorithms proposed in [G. Arampatzis, M. A. Katsoulakis, P. Plechac, M. Taufer, and L. Xu, J. Comput. Phys., 231 (2012), pp. 7795--7814] for the parallel simulation of spatially distributed particle systems on a lattice. FS-KMC are fractional step algorithms with a time-stepping window $\Delta t$, and as such they are inherently partially asynchronous since there is no processor communication during the period $\Delta t$. In this contribution we primarily focus on the error analysis of FS-KMC algorithms as approximations of conventional, serial KMC. …

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Mechanics Of Large Folds In Thin Interfacial Films, Vincent Demery, Benny Davidovitch, Christian Santangelo Jan 2014

Mechanics Of Large Folds In Thin Interfacial Films, Vincent Demery, Benny Davidovitch, Christian Santangelo

Christian Santangelo

A thin film confined to a liquid interface responds to uniaxial compression by wrinkling, and then by folding, that has been solved exactly before self-contact. Here, we address the mechanics of large folds, i.e., folds that absorb a length much larger than the wrinkle wavelength. With scaling arguments and numerical simulations, we show that the antisymmetric fold is energetically favorable and can absorb any excess length at zero pressure. Then, motivated by puzzles arising in the comparison of this simple model to experiments on lipid monolayers or capillary rafts, we discuss how to incorporate film weight, self-adhesion, or energy dissipation.

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Nonuniform Growth And Topological Defects In The Shaping Of Elastic Sheets, Nakul Bende, Ryan C. Hayward, Christian Santangelo Jan 2014

Nonuniform Growth And Topological Defects In The Shaping Of Elastic Sheets, Nakul Bende, Ryan C. Hayward, Christian Santangelo

Christian Santangelo

We demonstrate that shapes with zero Gaussian curvature, except at singularities, produced by the growth-induced buckling of a thin elastic sheet are the same as those produced by the Volterra construction of topological defects in which edges of an intrinsically flat surface are identified. With this connection, we study the problem of choosing an optimal pattern of growth for a prescribed developable surface, finding a fundamental trade-off between optimal design and the accuracy of the resulting shape which can be quantified by the length along which an edge should be identified.

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Comparing Monte Carlo Methods For Finding Ground States Of Ising Spin Glasses: Population Annealing, Simulated Annealing And Parallel Tempering, Wenlong Wang, Jonathan Machta, Helmut G. Katzgraber Jan 2014

Comparing Monte Carlo Methods For Finding Ground States Of Ising Spin Glasses: Population Annealing, Simulated Annealing And Parallel Tempering, Wenlong Wang, Jonathan Machta, Helmut G. Katzgraber

Jonathan Machta

Population annealing is a Monte Carlo algorithm that marries features from simulated annealing and parallel tempering Monte Carlo. As such, it is ideal to overcome large energy barriers in the free-energy landscape while minimizing a Hamiltonian. Thus, population annealing Monte Carlo can be used as a heuristic to solve combinatorial optimization problems. We illustrate the capabilities of population annealing Monte Carlo by computing ground states of the three-dimensional Ising spin glass with Gaussian disorder, whilst comparing to simulated annealing and parallel tempering Monte Carlo. Our results suggest that population annealing Monte Carlo is significantly more effiicient than simulated annealing but …

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Evidence Against A Mean-Field Description Of Short-Range Spin Glasses Revealed Through Thermal Boundary Conditions, Wenlong Wang, Jonathan Machta, Helmut G. Katzgraber Jan 2014

Evidence Against A Mean-Field Description Of Short-Range Spin Glasses Revealed Through Thermal Boundary Conditions, Wenlong Wang, Jonathan Machta, Helmut G. Katzgraber

Jonathan Machta

A theoretical description of the low-temperature phase of short-range spin glasses has remained elusive for decades. In particular, it is unclear if theories that assert a single pair of pure states, or theories that are based on infinitely many pure states—such as replica symmetry breaking—best describe realistic short-range systems. To resolve this controversy, the three-dimensional Edwards-Anderson Ising spin glass in thermal boundary conditions is studied numerically using population annealing Monte Carlo. In thermal boundary conditions all eight combinations of periodic vs antiperiodic boundary conditions in the three spatial directions appear in the ensemble with their respective Boltzmann weights, thus minimizing …

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Convectively Driven Shear And Decreased Heat Flux, David Goluskin, Hans Johnston, Glenn R. Flierl, Edward A. Spiegel Jan 2014

Convectively Driven Shear And Decreased Heat Flux, David Goluskin, Hans Johnston, Glenn R. Flierl, Edward A. Spiegel

Hans Johnston

We report on direct numerical simulations of two-dimensional, horizontally periodic Rayleigh–Bénard convection between free-slip boundaries. We focus on the ability of the convection to drive large-scale horizontal flow that is vertically sheared. For the Prandtl numbers (Pr) between 1 and 10 simulated here, this large-scale shear can be induced by raising the Rayleigh number (Ra) sufficiently, and we explore the resulting convection for Ra up to 1010. When present in our simulations, the sheared mean flow accounts for a large fraction of the total kinetic energy, and this fraction tends towards unity as Ra→∞. The shear helps disperse convective structures, …

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Measuring The Irreversibility Of Numerical Schemes For Reversible Stochastic Differential Equations, Markos Katsoulakis, Yannis Pantazis, Luc Rey-Bellet Jan 2014

Measuring The Irreversibility Of Numerical Schemes For Reversible Stochastic Differential Equations, Markos Katsoulakis, Yannis Pantazis, Luc Rey-Bellet

Markos Katsoulakis

For a stationary Markov process the detailed balance condition is equivalent to the time-reversibility of the process. For stochastic differential equations (SDE’s), the time discretization of numerical schemes usually destroys the time-reversibility property. Despite an extensive literature on the numerical analysis for SDE’s, their stability properties, strong and/or weak error estimates, large deviations and infinite-time estimates, no quantitative results are known on the lack of reversibility of discrete-time approximation processes. In this paper we provide such quantitative estimates by using the concept of entropy production rate, inspired by ideas from non-equilibrium statistical mechanics. The entropy production rate for a stochastic …

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Spatial Multi-Level Interacting Particle Simulations And Information Theory-Based Error Quantification, Evangelia Kalligiannaki, Markos Katsoulakis, Petr Plechac Jan 2014

Spatial Multi-Level Interacting Particle Simulations And Information Theory-Based Error Quantification, Evangelia Kalligiannaki, Markos Katsoulakis, Petr Plechac

Markos Katsoulakis

We propose a hierarchy of two-level kinetic Monte Carlo methods for sampling high-dimensional, stochastic lattice particle dynamics with complex interactions. The method is based on the efficient coupling of different spatial resolution levels, taking advantage of the low sampling cost in a coarse space and developing local reconstruction strategies from coarse-grained dynamics. Furthermore, a natural extension to a multilevel kinetic coarse-grained Monte Carlo is presented. Microscopic reconstruction corrects possibly significant errors introduced through coarse-graining, leading to the controlled-error approximation of the sampled stochastic process. In this manner, the proposed algorithm overcomes known shortcomings of coarse-graining of particle systems with complex …

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A Table Of Elliptic Curves Over The Cubic Field Of Discriminant −23, Steve Donnelly, Paul Gunnells, Ariah Klages-Mundt, Dan Yasaki Jan 2014

A Table Of Elliptic Curves Over The Cubic Field Of Discriminant −23, Steve Donnelly, Paul Gunnells, Ariah Klages-Mundt, Dan Yasaki

Paul Gunnells

Abstract. Let F be the cubic field of discriminant −23 and OF its ring of integers. Let 􀀀 be the arithmetic group GL2(OF ), and for any ideal n ⊂ OF let 􀀀0(n) be the congruence subgroup of level n. In [16], two of us (PG and DY) computed the cohomology of various 􀀀0(n), along with the action of the Hecke operators. The goal of [16] was to test the modularity of elliptic curves over F. In the present paper, we complement and extend the results of [16] in two ways. First, we tabulate more elliptic curves than were found …

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Low-Temperature Behavior Of The Statistics Of The Overlap Distribution In Ising Spin-Glass Models, Matthew Wittmann, B. Yucesoy, Helmut G. Katzgraber, Jonathan Machta, A. P. Young Jan 2014

Low-Temperature Behavior Of The Statistics Of The Overlap Distribution In Ising Spin-Glass Models, Matthew Wittmann, B. Yucesoy, Helmut G. Katzgraber, Jonathan Machta, A. P. Young

Jonathan Machta

Using Monte Carlo simulations, we study in detail the overlap distribution for individual samples for several spin-glass models including the infinite-range Sherrington-Kirkpatrick model, short-range Edwards-Anderson models in three and four space dimensions, and one-dimensional long-range models with diluted power-law interactions. We study three long-range models with different powers as follows: The first is approximately equivalent to a short-range model in three dimensions, the second to a short-range model in four dimensions, and the third to a short-range model in the mean-field regime. We study an observable proposed earlier by some of us which aims to distinguish the “replica symmetry breaking” …

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Muon-Spin Rotation Measurements Of The Vortex State In Sr2ruo4: Type-1.5 Superconductivity, Vortex Clustering And A Crossover From A Triangular To A Square Vortex Lattice, S.J. Ray, A.S. Gibbs, S.J. Bending, P.J. Curran, Egor Babaev, C. Baines, A.P. Mackenzie, S.L. Lee Jan 2014

Muon-Spin Rotation Measurements Of The Vortex State In Sr2ruo4: Type-1.5 Superconductivity, Vortex Clustering And A Crossover From A Triangular To A Square Vortex Lattice, S.J. Ray, A.S. Gibbs, S.J. Bending, P.J. Curran, Egor Babaev, C. Baines, A.P. Mackenzie, S.L. Lee

Egor Babaev

Muon-spin rotation has been used to probe the vortex state in Sr2RuO4. At moderate fields and temperatures a lattice of triangular symmetry is observed, crossing over to a lattice of square symmetry with increasing field and temperature. At lower fields it is found that there are large regions of the sample that are completely free from vortices which grow in volume as the temperature falls. Importantly this is accompanied by increasing vortex density and increasing disorder within the vortex-cluster-containing regions. Both effects are expected to result from the strongly temperature-dependent long-range vortex attractive forces arising from the multiband chiral-order superconductivity.

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Metaplectic Demazure Operators And Whittaker Functions, Gautam Chinta, Paul Gunnells, Anna Pusk´As Jan 2014

Metaplectic Demazure Operators And Whittaker Functions, Gautam Chinta, Paul Gunnells, Anna Pusk´As

Paul Gunnells

Abstract. In [CG10] the first two named authors defined an action of a Weyl group on rational functions and used it to construct multiple Dirichlet series. These series are related to Whittaker functions on an n-fold metaplectic cover of a reductive group. In this paper, we define metaplectic analogues of the Demazure and Demazure-Lusztig operators. We show how these operators can be used to recover the formulas from [CG10], and how, together with results of McNamara [McN], they can be used to compute Whittaker functions on metaplectic groups over p-adic fields.

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Skyrmions Induced By Dissipationless Drag In U(1) U (1) Superconductors, Julien Garaud, Karl A. H. Sellin, Juha JAykk, Egor Babaev Jan 2014

Skyrmions Induced By Dissipationless Drag In U(1) U (1) Superconductors, Julien Garaud, Karl A. H. Sellin, Juha JAykk, Egor Babaev

Egor Babaev

Rather generically, multicomponent superconductors and superfluids have intercomponent current-current interaction. We show that in superconductors with substantially strong intercomponent drag interaction, the topological defects which form in an external field are characterized by a skyrmionic topological charge. We then demonstrate that they can be distinguished from ordinary vortex matter by a very characteristic magnetization process due to the dipolar nature of inter-skyrmion forces. The results provide an experimental signature to confirm or rule out the formation p-wave state with reduced spin stiffness in p-wave superconductors.

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Microscopic Prediction Of Skyrmion Lattice State In Clean Interface Superconductors, Daniel F. Agterberg, Egor Babaev, Julien Garaud Jan 2014

Microscopic Prediction Of Skyrmion Lattice State In Clean Interface Superconductors, Daniel F. Agterberg, Egor Babaev, Julien Garaud

Egor Babaev

When an in-plane field is applied to a clean interface superconductor, a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like phase is stabilized. This phase has a U(1)×U(1) symmetry and, in principle, this symmetry allows for flux carrying topological excitations different from Abrikosov vortices (which are the simplest defects associated with S1 → S1 maps). However, in practice, largely due to electromagnetic and other intercomponent interactions, such topological excitations are very rare in superconducting systems. Here, we demonstrate that a realistic microscopic theory for interface superconductors, such as SrTiO3/LaAlO3, predicts an unconventional magnetic response where the flux-carrying objects are skyrmions, characterized by homotopy invariants of S2 …

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Topological Defects In Mixtures Of Superconducting Condensates With Different Charges, Julien Garaud, Egor Babaev Jan 2014

Topological Defects In Mixtures Of Superconducting Condensates With Different Charges, Julien Garaud, Egor Babaev

Egor Babaev

We investigate the topological defects in phenomenological models describing mixtures of charged condensates with commensurate electric charges. Such situations are expected to appear for example in liquid metallic deuterium. This is modeled by a multicomponent Ginzburg-Landau theory where the condensates are coupled to the same gauge field by different coupling constants whose ratio is a rational number. We also briefly discuss the case where electric charges are incommensurate. Flux quantization and finiteness of the energy per unit length dictate that the different condensates have different winding and thus different number of (fractional) vortices. Competing attractive and repulsive interactions lead to …

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