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Fluid dynamics in the warp drive spacetime geometry

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arXiv 2021年

作者： Santos-Pereira, Osvaldo L. Abreu, Everton M.C. Ribeiro, Marcelo Byrro Physics Institute Universidade Federal do Rio de Janeiro Brazil Physics Department Universidade Federal Rural do Rio de Janeiro Seropédica Brazil Physics Department Universidade Federal de Juiz de Fora Brazil Graduate Program in Applied Physics Physics Institute Universidade Federal do Rio de Janeiro Brazil Valongo Observatory Universidade Federal do Rio de Janeiro Brazil

The Alcubierre warp drive metric is a spacetime geometry featuring a spacetime distortion, called warp bubble, where a massive particle inside it acquires global superluminal velocities, or warp speeds. This work presents solutions of the Einstein equations for the Alcubierre metric having fluid matter as gravity source. The energy-momentum tensor considered two fluid contents, the perfect fluid and the parametrized perfect fluid (PPF), a tentative more flexible model whose aim is to explore the possibilities of warp drive solutions with positive matter density content. Santos-Pereira et al. (2020) already showed that the Alcubierre metric having dust as source connects this geometry to the Burgers equation, which describes shock waves moving through an inviscid fluid, but led the solutions back to vacuum. The same happened for two out of four solutions subcases for the perfect fluid. Other solutions for the perfect fluid indicate the possibility of warp drive with positive matter density, but at the cost of a complex solution for the warp drive regulating function. Regarding the PPF, solutions were also obtained indicating that warp speeds could be created with positive matter density. Weak, dominant, strong and null energy conditions were calculated for all studied subcases, being satisfied for the perfect fluid and creating constraints in the PPF quantities such that positive matter density is also possible for creating a warp bubble. Summing up all results, energy-momentum tensors describing more complex forms of matter, or field, distributions generate solutions for the Einstein equations with the warp drive metric where negative matter density might not be a strict precondition for attaining warp speeds. © 2021, CC BY.

关键词： Geometry

Charged dust solutions for the warp drive spacetime

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arXiv 2021年

作者： Santos-Pereira, Osvaldo L. Abreu, Everton M.C. Ribeiro, Marcelo Byrro Physics Institute Universidade Federal do Rio de Janeiro Brazil Department of Physics Universidade Federal Rural do Rio de Janeiro Seropédica Brazil Department of Physics Universidade Federal de Juiz de Fora Brazil Applied Physics Graduate Program Physics Institute Universidade Federal do Rio de Janeiro Brazil Valongo Observatory Universidade Federal do Rio de Janeiro Brazil

The Alcubierre warp drive metric is a spacetime construction where a massive particle located inside a spacetime distortion, called warp bubble, travels at velocities arbitrarily higher than the velocity of light. This theoretically constructed spacetime geometry is a consequence of general relativity where global superluminal velocities, also known as warp speeds, are possible, whereas local speeds are limited to subluminal ones as required by special relativity. In this work we analyze the solutions of the Einstein equations having charged dust energy-momentum tensor as source for warp velocities. The Einstein equations with the cosmological constant are written and all solutions having energy-momentum tensor components for electromagnetic fields generated by charged dust are presented, as well as the respective energy conditions. The results show an interplay between the energy conditions and the electromagnetic field such that in some cases the former can be satisfied by both positive and negative matter density. In other cases the dominant and null energy conditions are violated. A result connecting the electric energy density with the cosmological constant is also presented, as well as the effects of the electromagnetic field on the bubble dynamics. © 2021, CC BY.

关键词： Tensors

Quantifying yeast colony morphologies with feature engineering from time-lapse photography

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arXiv 2022年

作者： Goldschmidt, Andy Kunert-Graf, James Scott, Adrian C. Tan, Zhihao Dudley, Aimée M. Nathan Kutz, J. Department of Physics University of Washington SeattleWA98195 United States Pacific Northwest Research Institute SeattleWA98122 United States Molecular and Cellular Biology Graduate Program University of Washington SeattleWA98195 United States Department of Applied Mathematics University of Washington SeattleWA98195 United States

Baker's yeast (Saccharomyces cerevisiae) is a model organism for studying the morphology that emerges at the scale of multi-cell colonies. To look at how morphology develops, we collect a dataset of time-lapse photographs of the growth of different strains of S. cerevisiae. We discuss the general statistical challenges that arise when using time-lapse photographs to extract time-dependent features. In particular, we show how texture-based feature engineering and representative clustering can be successfully applied to categorize the development of yeast colony morphology using our dataset. The Local binary patterns (LBP) from image processing is used to score the surface texture of colonies. This texture score develops along a smooth trajectory during growth. The path taken depends on how the morphology emerges. A hierarchical clustering of the colonies is performed according to their texture development trajectories. The clustering method is designed for practical interpretability;it obtains the best representative colony image for any hierarchical sub-cluster. Copyright © 2022, The Authors. All rights reserved.

关键词： Morphology

Warp drive dynamic solutions considering different fluid sources

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arXiv 2021年

作者： Santos-Pereira, Osvaldo L. Abreu, Everton M.C. Ribeiro, Marcelo Byrro Physics Institute Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil Physics Department Universidade Federal Rural do Rio de Janeiro Seropédica Brazil Physics Department Universidade Federal de Juiz de Fora Juiz de Fora Brazil Applied Physics Graduate Program Physics Institute Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil

Alcubierre proposed in 1994 that the well known special relativistic limitation that particles cannot travel with velocities bigger than the light speed can be bypassed when such trips are considered globally within specific general relativistic frameworks. Although initial results indicated this scenario as being unphysical, since it would seem to require negative mass-energy density, recent theoretical analyses suggest that such an unphysical situation may not always be necessarily true. In this paper, we present solutions of the Einstein equations using the original Alcubierre warp drive metric endowed with various matter-energy sources, namely dust, perfect fluid, anisotropic fluid, and perfect fluid within a cosmological constant spacetime. A connection of some of these solutions featuring shock waves described by the Burgers equation is also shown. © 2021, CC BY.

关键词： Electromagnetic fields

exoALMA. VI. Rotating under Pressure: Rotation curves, azimuthal velocity substructures, and pressure variations

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arXiv 2025年

作者： Stadler, Jochen Benisty, Myriam Winter, Andrew J. Izquierdo, Andrés F. Longarini, Cristiano Galloway-Sprietsma, Maria Curone, Pietro Andrews, Sean M. Bae, Jaehan Facchini, Stefano Rosotti, Giovanni Teague, Richard Barraza-Alfaro, Marcelo Cataldi, Gianni Cuello, Nicolás Czekala, Ian Fasano, Daniele Flock, Mario Fukagawa, Misato Garg, Himanshi Hall, Cassandra Hammond, Iain Hilder, Thomas Huang, Jane Ilee, John D. Kanagawa, Kazuhiro Lesur, Geoffroy Lodato, Giuseppe Loomis, Ryan A. Menard, Francois Orihara, Ryuta Pinte, Christophe Price, Daniel J. Yen, Hsi-Wei Wafflard-Fernandez, Gaylor Wilner, David J. Wölfer, Lisa Yoshida, Tomohiro C. Zawadzki, Brianna Université Côte d’Azur Observatoire de la Côte d’Azur CNRS Laboratoire Lagrange France Königstuhl 17 Heidelberg69117 Germany NASA Hubble Fellowship Program United States Department of Astronomy University of Florida GainesvilleFL32611 United States Leiden Observatory Leiden University P.O. Box 9513 LeidenNL-2300 RA Netherlands European Southern Observatory Karl-Schwarzschild-Str. 2 Garching bei MünchenD-85748 Germany Institute of Astronomy University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom Dipartimento di Fisica Università degli Studi di Milano Via Celoria 16 Milano20133 Italy Departamento de Astronomía Universidad de Chile Camino El Observatorio 1515 Las Condes Santiago Chile Center for Astrophysics Harvard & Smithsonian CambridgeMA02138 United States Department of Earth Atmospheric and Planetary Sciences Massachusetts Institute of Technology CambridgeMA02139 United States National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Univ. Grenoble Alpes CNRS IPAG Grenoble38000 France School of Physics & Astronomy University of St. Andrews North Haugh St. AndrewsKY16 9SS United Kingdom School of Physics and Astronomy Monash University ClaytonVIC3800 Australia Department of Physics and Astronomy The University of Georgia AthensGA30602 United States Center for Simulational Physics The University of Georgia AthensGA30602 United States Institute for Artificial Intelligence The University of Georgia AthensGA30602 United States School of Physics and Astronomy Monash University VIC3800 Australia Department of Astronomy Columbia University 538 W. 120th Street Pupin Hall New YorkNY United States School of Physics and Astronomy University of Leeds LeedsLS2 9JT United Kingdom College of Science Ibaraki University 2-1-1 Bunkyo Ibaraki Mito310-8512 Japan National Radio Astronomy Observatory 520 Edgemont Rd. CharlottesvilleVA22903 United States Academia Sinica Institute of Ast

The bulk motion of the gas in protoplanetary disks around newborn stars is nearly Keplerian. By leveraging the high angular and spectral resolution of ALMA, we can detect small-scale velocity perturbations in molecular line observations caused by local gas pressure variations in the disk, possibly induced by embedded protoplanets. This paper presents the azimuthally averaged rotational velocity and its deviations from Keplerian rotation (δυ) for the exoALMA sample, as measured in the 12CO J = 3 − 2 and 13CO J = 3 − 2 emission lines. The rotation signatures show evidence for vertically stratified disks, in which 13CO rotates faster than 12CO due to a distinct thermal gas pressure gradient at their emitting heights. We find δυ-substructures in the sample on both small (∼10 au) and large (∼100 au) radial scales, reaching deviations up to 15% from background Keplerian velocity in the most extreme cases. More than 75% of the rings and 80% of the gaps in the dust continuum emission resolved in δυ are co-located with gas pressure maxima and minima, respectively. Additionally, gas pressure substructures are observed far beyond the dust continuum emission. For the first time, we determined the gas pressure derivative at the midplane from observations and found it to align well with the dust substructures within the given uncertainties. Based on our findings, we conclude that gas pressure variations are likely the dominant mechanism for ring and gap formation in the dust continuum. © 2025, CC BY.

关键词： Pressure gradient

The SRG/eROSITA All-Sky Survey: Dark Energy Survey Year 3 Weak Gravitational Lensing by eRASS1 selected Galaxy Clusters

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arXiv 2024年

作者： Grandis, S. Ghirardini, V. Bocquet, S. Garrel, C. Mohr, J.J. Liu, A. Kluge, M. Kimmig, L. Reiprich, T.H. Alarcon, A. Amon, A. Artis, E. Bahar, Y.E. Balzer, F. Bechtol, K. Becker, M.R. Bernstein, G. Bulbul, E. Campos, A. Carnero Rosell, A. Carrasco Kind, M. Cawthon, R. Chang, C. Chen, R. Chiu, I. Choi, A. Clerc, N. Comparat, J. Cordero, J. Davis, C. Derose, J. Diehl, H.T. Dodelson, S. Doux, C. Drlica-Wagner, A. Eckert, K. Elvin-Poole, J. Everett, S. Ferte, A. Gatti, M. Giannini, G. Giles, P. Gruen, D. Gruendl, R.A. Harrison, I. Hartley, W.G. Herner, K. Huff, E.M. Kleinebreil, F. Kuropatkin, N. Leget, P.F. Maccrann, N. McCullough, J. Merloni, A. Myles, J. Nandra, K. Navarro-Alsina, A. Okabe, N. Pacaud, F. Pandey, S. Prat, J. Predehl, P. Ramos, M. Raveri, M. Rollins, R.P. Roodman, A. Ross, A.J. Rykoff, E.S. Sanchez, C. Sanders, J. Schrabback, T. Secco, L.F. Seppi, R. Sevilla-Noarbe, I. Sheldon, E. Shin, T. Troxel, M. Tutusaus, I. Varga, T.N. Wu, H. Yanny, B. Yin, B. Zhang, X. Zhang, Y. Alves, O. Bhargava, S. Brooks, D. Burke, D.L. Carretero, J. Costanzi, M. da Costa, L.N. Pereira, M.E.S. De Vicente, J. Desai, S. Doel, P. Ferrero, I. Flaugher, B. Friedel, D. Frieman, J. García-Bellido, J. Gutierrez, G. Hinton, S.R. Hollowood, D.L. Honscheid, K. James, D.J. Jeffrey, N. Lahav, O. Lee, S. Marshall, J.L. Menanteau, F. Ogando, R.L.C. Pieres, A. Plazas Malagón, A.A. Romer, A.K. Sanchez, E. Schubnell, M. Smith, M. Suchyta, E. Swanson, M.E.C. Tarle, G. Weaverdyck, N. Weller, J. Universität Innsbruck Institut für Astro- und Teilchenphysik Technikerstr. 25/8 Innsbruck6020 Austria Max Planck Institute for Extraterrestrial Physics Giessenbachstrasse 1 Garching85748 Germany Faculty of Physics Ludwig-Maximilians-Universität München Scheinerstr. 1 Munich81679 Germany Universität Bonn Auf dem Hügel 71 Bonn53121 Germany Kavli Institute for Cosmology University of Cambridge Mading- ley Road CambridgeCB3 0HA United Kingdom Institute of Astronomy University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom Physics Department University of Wisconsin-Madison MadisonWI53706 United States Argonne National Laboratory 9700 South Cass Avenue LemontIL60439 United States Department of Physics and Astronomy University of Pennsylvania PhiladelphiaPA19104 United States Department of Physics Carnegie Mellon University PittsburghPA15312 United States Instituto de Astrofisica de Canarias Tenerife La LagunaE-38205 Spain Laboratório Interinstitucional de e-Astronomia - LIneA Rua Gal. José Cristino 77 RJ Rio de Janeiro20921-400 Brazil Universidad de La Laguna Dpto. Astrofísica Tenerife La LagunaE-38206 Spain Center for Astrophysical Surveys National Center for Supercom- puting Applications 1205 West Clark St. UrbanaIL61801 United States Department of Astronomy University of Illinois at Urbana-Champaign 1002 W. Green Street UrbanaIL61801 United States Physics Department William Jewell College LibertyMO64068 United States Department of Astronomy and Astrophysics University of Chicago ChicagoIL60637 United States Kavli Institute for Cosmological Physics University of Chicago ChicagoIL60637 United States Department of Physics Duke University DurhamNC27708 United States Department of Physics National Cheng Kung University Tainan70101 Taiwan NASA Goddard Space Flight Center 8800 Greenbelt Rd Green- belt MD20771 United States IRAP Université de Toulouse CNRS UPS CNES Toulouse France Jodrell Bank Center f

Context. Number counts of galaxy clusters across redshift are a powerful cosmological probe, if a precise and accurate reconstruction of the underlying mass distribution is performed - a challenge called mass calibration. With the advent of wide and deep photometric surveys, weak gravitational lensing by clusters has become the method of choice to perform this measurement. Aims. We measure and validate the weak gravitational lensing (WL) signature in the shape of galaxies observed in the first 3 years of the Dark Energy Survey (DES Y3) caused by galaxy clusters and groups selected in the first all-sky survey performed by SRG (Spectrum Roentgen Gamma)/eROSITA (eRASS1). These data are then used to determine the scaling between X-ray photon count rate of the clusters and their halo mass and redshift. Methods. We empirically determine the degree of cluster member contamination in our background source sample. The individual cluster shear profiles are then analysed with a Bayesian population model that self-consistently accounts for the lens sample selection and contamination, and includes marginalization over a host of instrumental and astrophysical systematics. To quantify the accuracy of the mass extraction of that model, we perform mass measurements on mock cluster catalogs with realistic synthetic shear profiles. This allows us to establish that hydro-dynamical modelling uncertainties at low lens redshifts (z © 2024, CC BY.

关键词： Calibration

Universal mechanical response of metallic glasses during strain-rate-dependent uniaxial compression

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arXiv 2022年

作者： Jin, Weiwei Datye, Amit Schwarz, Udo D. Shattuck, Mark D. O'Hern, Corey S. Department of Mechanical Engineering and Materials Science Yale University New HavenCT06520 United States Department of Chemical and Environmental Engineering Yale University New HavenCT06520 United States Benjamin Levich Institute Physics Department The City College of New York New YorkNY10031 United States Department of Physics Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States Graduate Program in Computational Biology and Bioinformatics Yale University New HavenCT06520 United States

Experimental data on the compressive strength σmax versus strain rate Ε eng for metallic glasses undergoing uniaxial compression shows significantly different behavior for different alloys. For some metallic glasses, σmax decreases with increasing Ε eng, for others, σmax increases with increasing Ε eng, and for others σmax versus Ε eng is nonmonotonic. Using numerical simulations of metallic glasses undergoing uniaxial compression at nonzero strain rate and temperature, we show that they obey a universal relation for the compressive strength versus temperature, which determines their mechanical response. At low Ε eng, increasing strain rate leads to increases in temperature and decreases in σmax∗, whereas at high Ε eng, increasing strain rate leads to decreases in temperature and increases in σmax∗. This non-monotonic behavior of σmax∗ versus temperature causes the nonmonotonic behavior of σmax∗ versus Ε eng. Variations in the internal dissipation change the characteristic strain rate at which the nonmonotonic behavior occurs. These results are general for a wide range of metallic glasses with different atomic interactions, damping coefficients, and chemical compositions. © 2022, CC BY.

关键词： Strain rate

BPS2025 - Understanding the molecular mechanism of the FLASH effect in radiation therapy using super-resolution microscopy

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Biophysical Journal 2025年第3期124卷 567a-567a页

作者： Henry Gatica-Gutierrez Prakash Joshi Gabriella Gagliano Sofia Vargas-Hernandez Alex Raterink Emil Schueler Anna-Karin Gustavsson Systems Synthetic and Physical Biology Graduate Program Rice University Houston TX USA Department of Radiation Physics University of Texas MD Anderson Cancer Center Houston TX USA Department of Chemistry Rice University Houston TX USA Applied Physics Graduate Program Rice University Houston TX USA Department of Cancer Biology University of Texas MD Anderson Cancer Center Houston TX USA

A Systematic Search of Distant Superclusters with the Subaru Hyper Suprime-Cam Survey

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arXiv 2024年

作者： Chen, Tsung-Chi Lin, Yen-Ting Schive, Hsi-Yu Oguri, Masamune Chen, Kai-Feng Okabe, Nobuhiro Ali, Sadman Bottrell, Connor Dalal, Roohi Koyama, Yusei Monteiro-Oliveira, Rogério Shimakawa, Rhythm Goto, Tomotsugu Hsieh, Bau-Ching Kodama, Tadayuki Nishizawa, Atsushi J. Institute of Astronomy and Astrophysics Academia Sinica Taipei10617 Taiwan Department of Physics National Taiwan University Taipei10617 Taiwan Graduate Institute of Astrophysics National Taiwan University Taipei10617 Taiwan Institute of Physics National Yang Ming Chiao Tung University Hsinchu30010 Taiwan Center for Theoretical Physics National Taiwan University Taipei10617 Taiwan Physics Division National Center for Theoretical Sciences Taipei10617 Taiwan Center for Frontier Science Chiba University Chiba-shi Chiba263-8522 Japan Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Physics Program Graduate School of Advanced Science and Engineering Hiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima Hiroshima739-8526 Japan Hiroshima Astrophysical Science Center Hiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima Hiroshima739-8526 Japan Core Research for Energetic Universe Hiroshima University 1-3-1 Kagamiyama Higashi-Hiroshima Hiroshima739-8526 Japan Subaru Telescope National Astronomical Observatory of Japan HiloHI96720 United States International Centre for Radio Astronomy Research University of Western Australia 35 Stirling Highway Perth6009 Australia Department of Astrophysical Sciences Princeton University PrincetonNJ08544 United States Waseda University 1-21-1 Nishi Waseda Shinjuku Tokyo169-0051 Japan Center for Data Science Waseda University 1-6-1 Nishi-Waseda Shinjuku Tokyo169-0051 Japan Institute of Astronomy National Tsing Hua University Hsinchu30013 Taiwan Astronomical Institute Graduate School of Science Tohoku University Sendai Miyagi980-8578 Japan DX Center Gifu Shotoku Gakuen University Gifu501-6194 Japan

Superclusters, encompassing environments across a wide range of overdensities, can be regarded as unique laboratories for studying galaxy evolution. Although numerous supercluster catalogs have been published, none of them goes beyond redshift z = 0.7. In this work, we adopt a physically motivated supercluster definition, requiring that superclusters should eventually collapse even in the presence of dark energy. Applying a friends-of-friends (FoF) algorithm to the CAMIRA cluster sample constructed using the Subaru Hyper Suprime-Cam survey data, we have conducted the first systematic search for superclusters at z = 0.5-1.0 and identified 673 supercluster candidates over an area of 1027 deg2. The FoF algorithm is calibrated by evolving N-body simulations to the far future to ensure high purity. We found that these high-z superclusters are mainly composed of 2 - 4 clusters, suggesting the limit of gravitationally bound structures in the younger Universe. In addition, we studied the properties of the clusters and brightest cluster galaxies (BCGs) residing in different large-scale environments. We found that clusters associated with superclusters are typically richer, but no apparent dependence of the BCG properties on large-scale structures is found. We also compared the abundance of observed superclusters with mock superclusters extracted from halo light cones, finding that photometric redshift uncertainty is a limiting factor in the performance of superclusters detection. © 2024, CC BY.

关键词： Dark energy