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arXiv 2021年

作者： Andersen, Bridget C. Bandura, Kevin Bhardwaj, Mohit Boyle, P.J. Brar, Charanjot Breitman, Daniela Cassanelli, Tomas Chatterjee, Shami Chawla, Pragya Cliche, Jean-François Cubranic, Davor Curtin, Alice P. Deng, Meiling Dobbs, Matt Dong, Fengqiu Adam Fonseca, Emmanuel Gaensler, B.M. Giri, Utkarsh Good, Deborah C. Hill, Alex S. Josephy, Alexander Kaczmarek, J.F. Kader, Zarif Kania, Joseph Kaspi, Victoria M. Leung, Calvin Li, D.Z. Lin, Hsiu-Hsien Masui, Kiyoshi W. McKinven, Ryan Mena-Parra, Juan Merryfield, Marcus Meyers, B.W. Michilli, D. Naidu, Arun Newburgh, Laura Ng, C. Ordog, Anna Patel, Chitrang Pearlman, Aaron B. Pen, Ue-Li Petroff, Emily Pleunis, Ziggy Rafiei-Ravandi, Masoud Rahman, Mubdi Ransom, Scott Renard, Andre Sanghavi, Pranav Scholz, Paul Shaw, J. Richard Shin, Kaitlyn Siegel, Seth R. Singh, Saurabh Smith, Kendrick Stairs, Ingrid Tan, Chia Min Tendulkar, Shriharsh P. Vanderlinde, Keith Wiebe, D.V. Wulf, Dallas Zwaniga, Andrew Department of Physics McGill University 3600 rue University MontréalQCH3A 2T8 Canada McGill Space Institute McGill University 3550 rue University MontréalQCH3A 2A7 Canada Lane Department of Computer Science and Electrical Engineering 1220 Evansdale Drive PO Box 6109 MorgantownWV26506 United States Center for Gravitational Waves and Cosmology West Virginia University Chestnut Ridge Research Building MorgantownWV26505 United States Department of Physics University of Toronto 60 St. George Street TorontoONM5S 1A7 Canada Dunlap Institute for Astronomy & Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada David A. Dunlap Department of Astronomy & Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada Cornell Center for Astrophysics and Planetary Science Cornell University IthacaNY14853 United States Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road VancouverBCV6T 1Z1 Canada Perimeter Institute for Theoretical Physics 31 Caroline Street N WaterlooONN25 2YL Canada Dominion Radio Astrophysical Observatory Herzberg Research Centre for Astronomy and Astrophysics National Research Council Canada PO Box 248 PentictonBCV2A 6J9 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Department of Computer Science Math Physics & Statistics University of British Columbia Okanagan Campus KelownaBCV1V 1V7 Canada Department of Physics and Astronomy West Virginia University PO Box 6315 MorgantownWV26506 United States MIT Kavli Institute for Astrophysics and Space Research Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Department of Physics Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Cahill Center for Astronomy and Astrophysics California Institute of Technology 1216 E California Boulevard PasadenaCA91125 United States

Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that are visible at distances of billions of light-years.1 The nature of their progenitors and their emission mechanism remain open astrophysical questions.2 Here we report the detection of the multi-component FRB 20191221A and the identification of a periodic separation of 216.8(1) ms between its components with a significance of 6.5σ. The long (∼ 3 s) duration and nine or more components forming the pulse profile make this source an outlier in the FRB population. Such short periodicity provides strong evidence for a neutron-star origin of the event. Moreover, our detection favours emission arising from the neutron-star magnetosphere,3,4 as opposed to emission regions located further away from the star, as predicted by some models.5 Copyright © 2021, The Authors. All rights reserved.

关键词： Magnetosphere

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A clock stabilization system for CHIME/FRB Outriggers

arXiv

引用

arXiv 2021年

作者： Mena-Parra, Juan Leung, C. Cary, S. Masui, K.W. Kaczmarek, J.F. Amiri, M. Bandura, K. Boyle, P.J. Cassanelli, T. Cliche, J.-F. Dobbs, M. Kaspi, V.M. Landecker, T.L. Lanman, A. Sievers, J.L. MIT Kavli Institute for Astrophysics and Space Research Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Department of Physics Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Department of Astronomy Wellesley College 106 Central Street WellesleyMA02481 United States National Research Council Canada Herzberg Astronomy and Astrophysics Research Centre Dominion Radio Astrophysical Observatory PO Box 248 PentictonBCV2A 6J9 Canada Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road VancouverBCV6T 1Z1 Canada Lane Department of Computer Science and Electrical Engineering 1220 Evansdale Drive PO Box 6109 MorgantownWV26506 United States Center for Gravitational Waves and Cosmology West Virginia University Chestnut Ridge Research Building MorgantownWV26505 United States Department of Physics McGill University 3600 rue University MontréalQCH3A 2T8 Canada McGill Space Institute McGill University 3550 rue University MontréalQCH3A 2A7 Canada Dunlap Institute for Astronomy & Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada David A. Dunlap Department of Astronomy & Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada Dominion Radio Astrophysical Observatory Herzberg Research Centre for Astronomy and Astrophysics National Research Council Canada PO Box 248 PentictonBCV2A 6J9 Canada Perimeter Institute for Theoretical Physics 31 Caroline Street N WaterlooONN25 2YL Canada School of Chemistry and Physics University of KwaZulu-Natal 238 Mazisi Kunene Rd Glenwood Durban4041 South Africa

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has emerged as the prime telescope for detecting fast radio bursts (FRBs). CHIME/FRB Outriggers will be a dedicated very-long-baseline interferometry (VLBI) instrument consisting of outrigger telescopes at continental baselines working with CHIME and its specialized real-time transient-search backend (CHIME/FRB) to detect and localize FRBs with 50 mas precision. In this paper we present a minimally invasive clock stabilization system that effectively transfers the CHIME digital backend reference clock from its original GPS-disciplined ovenized crystal oscillator to a passive hydrogen maser. This enables us to combine the long-term stability and absolute time tagging of the GPS clock with the short and intermediate-term stability of the maser to reduce the clock timing errors between VLBI calibration observations. We validate the system with VLBI-style observations of Cygnus A over a 400 m baseline between CHIME and the CHIME Pathfinder, demonstrating agreement between sky-based and maser-based timing measurements at the 30 ps rms level on timescales ranging from one minute to up to nine days, and meeting the stability requirements for CHIME/FRB Outriggers. In addition, we present an alternate reference clock solution for outrigger stations which lack the infrastructure to support a passive hydrogen maser. © 2021, CC BY.

关键词： Hydrogen

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No evidence for galactic latitude dependence of the fast radio burst sky distribution

arXiv

引用

arXiv 2021年

作者： Josephy, A. Chawla, P. Curtin, A.P. Kaspi, V.M. Bhardwaj, M. Boyle, P.J. Brar, C. Cassanelli, T. Fonseca, E. Gaensler, B.M. Leung, C. Lin, H.-H. Masui, K.W. Mckinven, R. Mena-Parra, J. Michilli, D. Ng, C. Pleunis, Z. Rafiei-Ravandi, M. Rahman, M. Sanghavi, P. Scholz, P. Shin, K. Smith, K.M. Stairs, I.H. Tendulkar, S.P. Zwaniga, A.V. Department of Physics McGill University 3600 rue University MontréalQCH3A 2T8 Canada McGill Space Institute McGill University 3550 rue University MontréalQCH3A 2A7 Canada Dunlap Institute for Astronomy and Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada David A. Dunlap Department of Astronomy and Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada MIT Kavli Institute for Astrophysics and Space Research Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Department of Physics Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Canadian Institute for Theoretical Astrophysics 60 St. George Street TorontoONM5S 3H8 Canada Perimeter Institute for Theoretical Physics 31 Caroline Street N WaterlooONN25 2YL Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Sidrat Research PO Box 73527 RPO Wychwood TorontoONM6C 4A7 Canada Lane Department of Computer Science and Electrical Engineering 1220 Evansdale Drive PO Box 6109 MorgantownWV26506 United States Center for Gravitational Waves and Cosmology West Virginia University Chestnut Ridge Research Building MorgantownWV26505 United States Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road VancouverBCV6T 1Z1 Canada Department of Astronomy and Astrophysics Tata Institute of Fundamental Research Mumbai400005 India National Centre for Radio Astrophysics Post Bag 3 Ganeshkhind Pune411007 India

We investigate whether the sky rate of Fast Radio Bursts depends on Galactic latitude using the first catalog of Fast Radio Bursts (FRBs) detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Project. We first select CHIME/FRB events above a specified sensitivity threshold in consideration of the radiometer equation, and then compare these detections with the expected cumulative time-weighted exposure using Anderson-Darling and Kolmogrov-Smirnov tests. These tests are consistent with the null hypothesis that FRBs are distributed without Galactic latitude dependence (p-values distributed from 0.05 to 0.99, depending on completeness threshold). Additionally, we compare rates in intermediate latitudes (|b| Copyright © 2021, The Authors. All rights reserved.

关键词： Astrophysics

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Sub-second periodicity in a fast radio burst

Research Square

引用

Research Square 2021年

作者： Andersen, Bridget C. Bandura, Kevin Bhardwaj, Mohit Boyle, P.J. Brar, Charanjot Breitman, Daniela Cassanelli, Tomas Chatterjee, Shami Chawla, Pragya Cliche, Jean-François Cubranic, Davor Curtin, Alice P. Deng, Meiling Dobbs, Matt Dong, Fengqiu Adam Fonseca, Emmanuel Gaensler, B.M. Giri, Utkarsh Good, Deborah C. Hill, Alex S. Josephy, Alexander Kaczmarek, J.F. Kader, Zarif Kania, Joseph Kaspi, Victoria M. Leung, Calvin Li, D.Z. Lin, Hsiu-Hsien Masui, Kiyoshi W. McKinven, Ryan Mena-Parra, Juan Merryfield, Marcus Meyers, B.W. Michilli, D. Naidu, Arun Newburgh, Laura Ng, C. Ordog, Anna Patel, Chitrang Pearlman, Aaron B. Pen, Ue-Li Petroff, Emily Pleunis, Ziggy Rafiei-Ravandi, Masoud Rahman, Mubdi Ransom, Scott Renard, Andre Sanghavi, Pranav Scholz, Paul Richard Shaw, J. Shin, Kaitlyn Siegel, Seth R. Singh, Saurabh Smith, Kendrick Stairs, Ingrid Tan, Chia Min Tendulkar, Shriharsh P. Vanderlinde, Keith Wiebe, D.V. Wulf, Dallas Zwaniga, Andrew Michilli, Daniele McGill University Canada Department of Physics McGill University 3600 rue University MontréalQCH3A 2T8 Canada McGill Space Institute McGill University 3550 rue University MontréalQCH3A 2A7 Canada Lane Department of Computer Science and Electrical Engineering 1220 Evansdale Drive PO Box 6109 MorgantownWV26506 United States Center for Gravitational Waves and Cosmology West Virginia University Chestnut Ridge Research Building MorgantownWV26505 United States Department of Physics University of Toronto 60 St. George Street TorontoONM5S 1A7 Canada Dunlap Institute for Astronomy & Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada David A. Dunlap Department of Astronomy & Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada Cornell Center for Astrophysics and Planetary Science Cornell University IthacaNY14853 United States Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road VancouverBCV6T 1Z1 Canada Perimeter Institute for Theoretical Physics 31 Caroline Street N WaterlooONN25 2YL Canada Dominion Radio Astrophysical Observatory Herzberg Research Centre for Astronomy and Astrophysics National Research Council Canada PO Box 248 PentictonBCV2A 6J9 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Department of Computer Science Math Physics & Statistics University of British Columbia Okanagan Campus KelownaBCV1V 1V7 Canada Department of Physics and Astronomy West Virginia University PO Box 6315 MorgantownWV26506 United States MIT Kavli Institute for Astrophysics and Space Research Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Department of Physics Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Cahill Center for Astronomy and Astrophysics California Institute of Technology 1216 E California Boulevard Pasaden

The origin of fast radio bursts (FRBs)1, millisecond-duration flashes of radio waves that are visible at distances of billions of light-years, remains an open astrophysical question.2 Here we report the detection of the multi-component FRB 20191221A with the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB), and the identification of a periodic separation of 216.8(1) ms between its components with a significance of 6.5σ. The long (∼3 s) duration and nine or more components forming the pulse profile make this source an outlier in the FRB population. We also report two additional FRBs, 20210206A and 20210213A, whose multi-component pulse profiles show some indication of periodic separations of 2.8(1) and 10.7(1) ms, respectively, suggesting the possible existence of a group of FRBs with complex and periodic pulse profiles. Such short periodicities provide strong evidence for a neutron-star origin of these events. Moreover, our detections favour emission arising from the neutron-star magnetosphere,3 as opposed to emission regions located further away from the star, as predicted by some models.4 Possible explanations for the observed periodicity include super-giant pulses from a neutron star that are possibly related to a magnetar outburst and interacting neutron stars in a binary system. © 2021, CC BY.

关键词： Magnetosphere

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The First CHIME/FRB Fast Radio Burst Catalog

arXiv

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arXiv 2021年

作者： Amiri, Mandana Andersen, Bridget C. Bandura, Kevin Berger, Sabrina Bhardwaj, Mohit Boyce, Michelle M. Boyle, P.J. Brar, Charanjot Breitman, Daniela Cassanelli, Tomas Chawla, Pragya Chen, Tianyue Cliche, J.-F. Cook, Amanda Cubranic, Davor Curtin, Alice P. Deng, Meiling Dobbs, Matt Dong, Fengqiu Adam Eadie, Gwendolyn Fandino, Mateus Fonseca, Emmanuel Gaensler, B.M. Giri, Utkarsh Good, Deborah C. Halpern, Mark Hill, Alex S. Hinshaw, Gary Josephy, Alexander Kaczmarek, Jane F. Kader, Zarif Kania, Joseph W. Kaspi, Victoria M. Landecker, T.L. Lang, Dustin Leung, Calvin Li, Dongzi Lin, Hsiu-Hsien Masui, Kiyoshi W. McKinven, Ryan Mena-Parra, Juan Merryfield, Marcus Meyers, Bradley W. Michilli, Daniele Milutinovic, Nikola Mirhosseini, Arash Münchmeyer, Moritz Naidu, Arun Newburgh, Laura Ng, Cherry Patel, Chitrang Pen, Ue-Li Petroff, Emily Pinsonneault-Marotte, Tristan Pleunis, Ziggy Rafiei-Ravandi, Masoud Rahman, Mubdi Ransom, Scott M. Renard, Andre Sanghavi, Pranav Scholz, Paul Shaw, J. Richard Shin, Kaitlyn Siegel, Seth R. Sikora, Andrew E. Singh, Saurabh Smith, Kendrick M. Stairs, Ingrid Tan, Chia Min Tendulkar, S.P. Vanderlinde, Keith Wang, Haochen Wulf, Dallas Zwaniga, A.V. Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road VancouverBCV6T 1Z1 Canada Department of Physics McGill University 3600 rue University MontréalQCH3A 2T8 Canada McGill Space Institute McGill University 3550 rue University MontréalQCH3A 2A7 Canada Lane Department of Computer Science and Electrical Engineering 1220 Evansdale Drive PO Box 6109 MorgantownWV26506 United States Center for Gravitational Waves and Cosmology West Virginia University Chestnut Ridge Research Building MorgantownWV26505 United States Department of Physics and Astronomy University of Manitoba WinnipegMBR3T 2N2 Canada Department of Physics University of Toronto 60 St. George Street TorontoONM5S 1A7 Canada Dunlap Institute for Astronomy & Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada David A. Dunlap Department of Astronomy & Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada Mit Kavli Institute for Astrophysics and Space Research Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Perimeter Institute for Theoretical Physics 31 Caroline Street N WaterlooONN25 2YL Canada Dominion Radio Astrophysical Observatory Herzberg Research Centre for Astronomy and Astrophysics National Research Council Canada PO Box 248 PentictonBCV2A 6J9 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Department of Computer Science Math Physics & Statistics University of British Columbia KelownaBCV1V 1V7 Canada Department of Physics and Astronomy West Virginia University PO Box 6315 MorgantownWV26506 United States Department of Physics Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States Canadian Institute for Theoretical Astrophysics 60 St. George Street TorontoONM5S 3H8 Canada Department of Physics University of Wisconsin-Madison 1150 University Ave Mad

We present a catalog of 536 fast radio bursts (FRBs) detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Project between 400 and 800 MHz from 2018 July 25 to 2019 July 1, including 62 bursts from 18 previously reported repeating sources. The catalog represents the first large sample, including bursts from repeaters and non-repeaters, observed in a single survey with uniform selection effects. This facilitates comparative and absolute studies of the FRB population. We show that repeaters and apparent non-repeaters have sky locations and dispersion measures (DMs) that are consistent with being drawn from the same distribution. However, bursts from repeating sources differ from apparent non-repeaters in intrinsic temporal width and spectral bandwidth. Through injection of simulated events into our detection pipeline, we perform an absolute calibration of selection effects to account for systematic biases. We find evidence for a population of FRBs-comprising a large fraction of the overall population-with a scattering time at 600 MHz in excess of 10 ms, of which only a small fraction are observed by CHIME/FRB. We infer a powerlaw index for the cumulative fluence distribution of α = -1.40 ± 0.11(stat.)-0.09+0.06(sys.), consistent with the -3/2 expectation for a non-evolving population in Euclidean space. We find α is steeper for high-DM events and shallower for low-DM events, which is what would be expected when DM is correlated with distance. We infer a sky rate of [525 ± 30(stat.)-130+140(sys.)]/sky/day above a fluence of 5 Jy ms at 600 MHz, with scattering time at 600 MHz under 10 ms, and DM above 100 pc cm-3 Copyright © 2021, The Authors. All rights reserved.

关键词： Radio astronomy

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The evolutionary history of 2,658 cancers (vol 578, pg 122, 2020)

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NATURE 2023年第7948期614卷 E42-E42页

作者： Gerstung, Moritz Jolly, Clemency Leshchiner, Ignaty Dentro, Stefan C. Gonzalez, Santiago Rosebrock, Daniel mitchell, Thomas J. Rubanova, Yulia Anur, Pavana Yu, Kaixian Tarabichi, Maxime Deshwar, Amit Wintersinger, Jeff Kleinheinz, Kortine Vazquez-Garcia, Ignacio Haase, Kerstin Jerman, Lara Sengupta, Subhajit Macintyre, Geoff Malikic, Salem Donmez, Nilgun Livitz, Dimitri G. Cmero, Marek Demeulemeester, Jonas Schumacher, Steven Fan, Yu Yao, Xiaotong Lee, Juhee Schlesner, Matthias Boutros, Paul C. Bowtell, David D. Zhu, Hongtu Getz, Gad Imielinski, Marcin Beroukhim, Rameen Sahinalp, S. Cenk Ji, Yuan Peifer, Martin Markowetz, Florian Mustonen, Ville Yuan, Ke Wang, Wenyi Morris, Quaid D. Spellman, Paul T. Wedge, David C. Van Loo, Peter European Molecular Biology Laboratory European Bioinformatics Institute (EMBL-EBI) Cambridge UK European Molecular Biology Laboratory Genome Biology Unit Heidelberg Germany Wellcome Sanger Institute Cambridge UK Genome Biology Unit European Molecular Biology Laboratory (EMBL) Heidelberg Germany University of Ljubljana Ljubljana Slovenia The Francis Crick Institute London UK Big Data Institute University of Oxford Oxford UK Wellcome Sanger Institute Wellcome Genome Campus Hinxton UK Big Data Institute Li Ka Shing Centre University of Oxford Oxford UK University of Cambridge Cambridge UK Cambridge University Hospitals NHS Foundation Trust Cambridge UK Department of Applied Mathematics and Theoretical Physics Centre for Mathematical Sciences University of Cambridge Cambridge UK Department of Epidemiology and Biostatistics Memorial Sloan Kettering Cancer Center New York NY USA Department of Statistics Columbia University New York NY USA Department of Haematology University of Cambridge Cambridge UK University of Leuven Leuven Belgium Broad Institute of MIT and Harvard Cambridge MA USA Center for Cancer Research Massachusetts General Hospital Charlestown MA USA Department of Pathology Massachusetts General Hospital Boston MA USA Harvard Medical School Boston MA USA Center for Cancer Research Massachusetts General Hospital Boston MA USA Dana-Farber Cancer Institute Boston MA USA Department of Medical Oncology Dana-Farber Cancer Institute Boston MA USA Department of Cancer Biology Dana-Farber Cancer Institute Boston MA USA Oxford NIHR Biomedical Research Centre Oxford UK Oxford NIHR Biomedical Research Centre University of Oxford Oxford UK University of Toronto Toronto Ontario Canada Vector Institute Toronto Ontario Canada Vector Institute Toronto ON Canada Department of Computer Science University of Toronto Toronto ON Canada Ontario Institute for Cancer Research Toronto Ontario Canada University of California Los Angeles

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On the hardness of learning with rounding over small modulu 13th

On the hardness of learning with rounding over small modulu

引用

13th International Conference on Theory of Cryptography, TCC 2016

作者： Bogdanov, Andrej Guo, Siyao Masny, Daniel Richelson, Silas Rosen, Alon Department of Computer Science and Engineering Chinese University of Hong Kong Hong Kong Ruhr-Universität Bochum Bochum Germany Department of Electrical Engineering and Computer Science MIT Cambridge United States Efi Arazi School of Computer Science IDC Herzliya Herzliya Israel

ISBN: (纸本)9783662490952

We show the following reductions from the learning with errors problem (LWE) to the learning with rounding problem (LWR): (1) Learning the secret and (2) distinguishing samples from random strings is at least as hard for LWR as it is for LWE for efficient algorithms if the number of samples is no larger than O(q/Bp), where q is the LWR modulus, p is the rounding modulus, and the noise is sampled from any distribution supported over the set {−B, . . . , B}. Our second result generalizes a theorem of Alwen, Krenn, Pietrzak, and Wichs (CRYPTO 2013) and provides an alternate proof of it. Unlike Alwen et al., we do not impose any number theoretic restrictions on the modulus q. The first result also extends to variants of LWR and LWE over polynomial rings. The above reductions are sample preserving and run in time poly(n, q,m). As additional results we show that (3) distinguishing any number of LWR samples from random strings is of equivalent hardness to LWE whose noise distribution is uniform over the integers in the range [−q/2p, . . . , q/2p) provided q is a multiple of p and (4) the "noise flooding" technique for converting faulty LWE noise to a discrete Gaussian distribution can be applied whenever q = Ω(B √ m). © International Association for Cryptologic Research 2016.

关键词： Hardness

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Macroscopic scaling of high-order harmonics generated by two-color optimized waveforms in a hollow waveguide

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Physical Review A 2017年第1期96卷 013422-013422页

作者： Cheng Jin Kyung-Han Hong C. D. Lin Department of Applied Physics Nanjing University of Science and Technology Nanjing Jiangsu 210094 People's Republic of China Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics Massachusetts Institute of Technology (MIT) Cambridge Massachusetts 02139 USA J. R. Macdonald Laboratory Department of Physics Kansas State University Manhattan Kansas 66506 USA

We present the macroscopic scaling of high harmonics generated by two-color laser pulses interacting with Ne gas in a hollow waveguide. We demonstrate that the divergence of harmonics is inversely proportional to the waveguide radius and harmonic yields are proportional to the square of the waveguide radius when the gas pressure and waveguide length are chosen to meet the phase-matching condition. We also show that harmonic yields are inversely proportional to the ionization level of the optimized two-color waveform with proper gas pressure if waveguide radius and length are fixed. These scaling relations would help experimentalists find phase-matching conditions to efficiently generate tabletop high-flux coherent soft x rays for applications.

关键词： High-order harmonic generation Ultrafast phenomena

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Photophysics of GaN single photon sources in the visible spectral range

arXiv

引用

arXiv 2017年

作者： Berhane, Amanuel M. Jeong, Kwang-Yong Bradac, Carlo Walsh, Michael Englund, Dirk Toth, Milos Aharonovich, Igor School of Mathematical and Physical Sciences University of Technology Sydney UltimoNSW2007 Australia Department of Electrical Engineering and Computer Science MIT CambridgeMA02139 United States Department of Nano Science and Technology Gachon University Gyeonggi-do13120 Korea Republic of

In this work, we present a detailed photophysical analysis of recently-discovered optically stable, single photon emitters (SPEs) in Gallium Nitride (GaN). Temperature-resolved photoluminescence measurements reveal that the emission lines at 4 K are three orders of magnitude broader than the transform-limited widths expected from excited state lifetime measurements. The broadening is ascribed to ultra-fast spectral diffusion. Continuing the photophysics study on several emitters at room temperature (RT), a maximum average brightness of ~(427±215) kCounts/s is measured. Furthermore, by determining the decay rates of emitters undergoing three-level optical transitions, radiative and non-radiative lifetimes are calculated at RT. Finally, polarization measurements from 14 emitters are used to determine visibility as well as dipole orientation of defect systems within the GaN crystal. Our results underpin some of the fundamental properties of SPE in GaN both at cryogenic and RT, and define the benchmark for future work in GaN-based single-photon technologies. Copyright © 2017, The Authors. All rights reserved.

关键词： III-V semiconductors

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Improved Temporal Calibration of Tracked Ultrasound: An Open-Source Solution

引用

Journal of Medical Robotics Research 2017年第4期2卷

作者： Moult, Eric M. Lasso, Andras Ungi, Tamas Pinter, Csaba Welch, Mattea Fichtinger, Gabor Department of Electrical Engineering and Computer Science MIT Cambridge MA United States School of Computing Queen's University Kingston ON Canada Department of Medical Biophysics University of Toronto Toronto ON Canada

In tracked ultrasound systems, temporal misalignment between image and tracker data results in incorrect image pose. We present a fully automatic temporal calibration. We image a flat plate in water with a tracked probe undergoing periodic uniaxial freehand translation. Using robust line detection scheme, we compute temporal misalignment as difference between probe and corresponding image position. From 240 sequences, standard deviation was under 5 ms for standard imaging parameters. Source code is available in Public Library for Ultrasound Research, PLUS (***). © 2017 World Scientific Publishing Company.

关键词： PLUS temporal calibration Tracked ultrasound ultrasound calibration

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