Pairs of Supermassive Black Holes May Be Rarer Than Earlier Thought

Image by David Roberts

Image by David Roberts

Recent research by David H. Roberts, William R. Kenan, Jr. Professor of Astrophysics at Brandeis, has shown that pairs of supermassive black holes at the centers of galaxies are less common than previously thought. This suggests that the level of gravitational radiation from such systems is lower than earlier predicted. This work was in collaboration with Lakshmi Saripalli and Ravi Subrahmanyan of the Raman Research Institute in Bangalore, and much of the work was done by Brandeis undergraduate students Jake Cohen and Jing Liu. It has recently been published in a pair of papers in the Astrophysical Journal Supplements and Astrophysical Journal Letters.

Gravitational waves are ripples in space-time predicted by Einstein’s 1915 General Theory of Relativity. Propagating at the speed of light, they are produced in astrophysical events such as supernovae and close binary stars.

No direct experimental evidence of the existence of gravitational waves has been found to date. We know that they exist because they sap energy from the orbits of binary systems, and using ultra-precise radio astronomy it has been shown that the changes in binary orbits of pairs of pulsars (magnetized neutron stars) are precisely as predicted by General Relativity. Hulse and Taylor were awarded the Nobel Prize in Physics for their contributions to this work.

The largest source of gravitational waves is expected to be the coalescence of pairs of supermassive black holes in the centers of large galaxies. We know today that galaxies grow by mergers, and that every galaxy harbors a massive black hole at its center, with mass roughly proportional to the galaxy’s mass. When two massive galaxies merge to form a larger galaxy, it will contain a pair of black holes instead of a single one. Through a process involving the gravitational scattering of ordinary stars the two black holes migrate toward each other and eventually coalesce into a single even more massive black hole. The process of coalescence involves “strong gravity,” that is, it occurs when the separation of the two merging black holes becomes comparable to their Schwarzschild radii. Recent developments in numerical relativity have made it possible to study the coalescence process in the computer, and predictions may be made about the details of the gravitational waves that emerge. Thus direct detection of gravitational waves will enable tests of General Relativity not achievable any other way.

In order to predict the amount of gravitational radiation present in the Universe it is necessary to estimate by other methods the rate at which massive galaxies are colliding and their black holes coalescing. One way to do this is to examine the small number of radio galaxies that have unusual morphologies that suggest that they were created by the process of a spin-flip of a supermassive black hole due to its interaction with a second supermassive black hole. These are the so-called “X-shaped radio galaxies” (“XRGs”), and a naive counting of their numbers suggests that they are about 6% of all radio galaxies. Using this and knowing the lifetime of such an odd radio structure it is possible to determine the rate at which massive galaxies are merging and their black holes coalescing.

Roberts et al. re-examined this idea, and made a critical assessment of the mechanism of formation of XRGs. It turns out that other mechanisms can easily create such odd structures, and according to their work the large majority of XRGs are not the result of black hole-black hole mergers at all. They suggest as a result that the rate of supermassive black hole mergers may have been overestimated by a factor of three to five, with the consequence that the Universe contains that much less gravitational radiation than previously believed. In fact, recent results from searches for such gravitational waves have set upper limits below previous predictions, as might expect from this work.

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IGERT Summer Institute – July 27 to August 7, 2015

IGERTBrandeis is hosting a two-week summer institute for graduate students in the mathematical sciences from July 27-August 7.  This will combine the annual summer institute of Brandeis’ Geometry and Dynamics IGERT program, with a sequel to the US-India Advanced Studies Institute on thermalization, held two years ago in Bangalore.

Topics:

  • Large deviation theory
  • Statistics of extreme events
  • The large N expansion in statistical and quantum physics
  • Statistical fluid dynamics
  • Quantum information and quantum gravity
  • Thermalization in Quantum Systems

Lecturers:

Sumit Das (U. Kentucky)
Chandan Dasgupta (IISC, Bangalore)
Rajesh Gopakumar (HRI, Allahabad and ICTS)
Alex Maloney (McGill University)
Satya Majumdar (LPTMS, Paris)
Sanjib Sabhapandit (Raman Research Institute, Bangalore)
Peter Weichman (BAE systems)

Organizers:

Albion Lawrence
Bulbul Chakraborty

Registration:

There will be no registration fee, but the venue will have limited capacity, so interested students should register by sending an email to Catherine Broderick (cbroderi@brandeis.edu) by July 4. Please list your affiliation, your year in graduate school, any publications, and the name of your PhD advisor.

Additional information can be found at www.brandeis.edu/igert/.

New Faculty Member Joins the Physics Department

A new faculty member is joining the Physics department starting on January 1, 2016.

W. Benjamin RogersW. Benjamin (Ben) Rogers is currently a research associate in Applied Physics at Harvard University under the supervision of Professor Vinothan Manoharan. Before coming to Harvard, he completed his Ph.D. in the Department of Chemical and Biomolecular Engineering at the University of Pennsylvania and his B.S. in Chemical Engineering from the University of Delaware.

Ben’s research focuses on developing quantitative tools and design strategies to understand and control the self-assembly of soft matter. He is interested in elucidating the role of specificity in complex self-assembly, designing responsive nanoscale materials by controlling phase transitions in colloidal suspensions, and understanding how coupled chemical reactions give rise to active materials, which can move, organize, repair, or replicate. At the intersection of soft condensed matter, biophysics, and DNA nanotechnology, his research utilizes techniques from synthetic chemistry, optical microscopy, micromanipulation, and statistical mechanics.

7 Division of Science Faculty Recently Promoted

Congratulations to the following 7 Division of Science faculty members were recently promoted:

katz_dbDonald B. Katz (Psychology) has been promoted to Professor of Psychology. Don came to Brandeis as an Assistant Professor with a joint appointment in the Volen Center for Complex Systems in 2002 and was promoted to Associate Professor and awarded tenure in 2008. Don’s teaching and research serve central roles in both Psychology and the Neuroscience program. His systems approach to investigating gustation blends behavioral testing of awake rodents with multi-neuronal recording and pharmacological, optogenetic, and modelling techniques. Broad themes of the neural dynamics of perceptual coding, learning, social learning, decision making, and insight run through his work on gustation. For his research, Don has won the 2007 Polak Award and the 2004 Ajinomoto Young Investigator in Gustation Award, both from the Association for Chemoreception Sciences. Don has taught “Introduction to Behavioral Neuroscience” (NPSY11b), “Advanced Topics in Behavioral Neuroscience” (NPSY197a), “Neuroscience Proseminar” (NBIO250a), “Proseminar in Brain, Body, and Behavior II” (PSYC302a), “How Do We Know What We Know?” (SYS1c). For his excellence in teaching, Don has been recognized with the 2013 Jeanette Lerman-Neubauer ’69 and Joseph Neubauer Prize for Excellence in Teaching and Mentoring, the 2006 Brandeis Student Union Teaching Award, and the 2006 Michael L. Walzer Award for Teaching and Scholarship.

Nicolas RohlederNicolas Rohleder (Psychology) has been promoted to Associate Professor in Psychology. Nic is a member of the Volen Center for Complex Systems and on the faculty of the Neuroscience and Health, Science, Society and Policy programs. His course offerings include “Health Psychology” (PSYC38a), “Stress, Physiology and Health” (NPSY141a), and” Research Methods and Laboratory in Psychology” (PSYC52a). Nic’s research investigates how acute and chronic or repeated stress experiences affect human health across individuals and age groups. His laboratory performs studies with human participants using methods than span behavioral to molecular to understand how the hypothalamus-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS) regulate peripheral immunological responses and how these processes mediate cardiovascular disease, type 2 diabetes, and cancer, and aging. His research and teaching fill unique niches for all his Brandeis departmental and program affiliations. Nic’s research excellence has been recognized outside Brandeis with awards including the 2013 Herbert Weiner Early Career Award of the American Psychosomatic Society and the 2011 Curt P. Richter Award of the International Society of Psychoneuroendocrinology.

Matthew HeadrickMatthew Headrick (Physics) has been promoted to Associate Professor of Physics. He works at the intersection of three areas of modern theoretical physics: quantum field theory, general relativity, and quantum information theory. In particular, he uses information-theoretic techniques to study the structure of entanglement — a fundamental and ubiquitous property of quantum systems — in various kinds of field theories. Much of his work is devoted to the study of so-called “holographic” field theories, which are equivalent, in a subtle and still mysterious way, to theories of gravity in higher-dimensional spacetimes. Holographic theories have revealed a deep connection between entanglement and spacetime geometry, and Headrick has made significant contributions to the elucidation of this connection. Understanding the role of entanglement in holographic theories, and in quantum gravity more generally, may eventually lead to an understanding of the microscopic origin of space and time themselves.

Isaac Krauss

Isaac Krauss (Chemistry) has been promoted to Associate Professor of Chemistry. He is an organic chemist and chemical biologist whose research is at the interface of carbohydrate chemistry and biology. His lab has devised tools for directed evolution of modified DNA and peptides as an approach to designing carbohydrate vaccines against HIV. Krauss is also a very popular teacher and the recipient of the 2015 Walzer prize in teaching for tenure-track faculty.

Xiaodong Liu (Psychology) has been promoted to Associate Professor in Psychology. Xiaodong provides statistical training for graduate students in Psychology, Heller School, IBS, Neuroscience, Biology, and Computer Science, he serves as a statistical consultant for Xiaodong LiuPsychology faculty and student projects, and he performs research on general & generalized linear modeling and longitudinal data analysis, which he applies to child development, including psychological adjustment and school performance. He teaches “Advanced Psychological Statistics I and II” (PSYC210a,b), “SAS Applications” (PSYC140a), “Multivariate Statistics I: Applied Structural Equation Modeling” (PSYC215a), and “Multivariate Statistics II: Applied Hierarchical Linear Models” (PSYC216a). He is developing a new course on “The R Statistical Package and Applied Bayes Analysis”, and he recently won a Provost’s Innovations in Teaching Grant for “Incorporating Project-based modules in Learning and Teaching of Applied Statistics”.

Gabriella SciollaGabriella Sciolla (Physics) has been promoted to Professor of Physics. She is a particle physicist working on the ATLAS experiment at CERN in Geneva, Switzerland. Sciolla and her group study the properties of the newly discovered Higgs Boson and search for Dark Matter particles produced in high-energy proton-proton collisions at the Large Hadron Collider. Sciolla is also responsible for the reconstruction and calibration of the muons produced in ATLAS. These particles are key to both Higgs studies and searches for New Physics.

Nianwen Xue (Computer Science) has been promoted to Associate Professor of Computer Science.  The Computer Science Department is pleased to annNianwen Xueounce the promotion of Nianwen (Bert) Xue to Associate Professor with tenure. Since joining Computer Science he has made significant contributions to the research and teaching efforts in Computational Linguistics, including growing a masters program from zero up to 18 students this year. His publications are very well regarded, and focus on the development and use of large corpora for natural language processing, especially in Chinese. He has built a sizable lab with diverse funding that students from around the world are vying to enter.

Thank you to the following department chairs for their contributions to this post:

  • Paul DiZio, Psychology
  • Jane Kondev, Physics
  • Jordan Pollack, Computer Science
  • Barry Snider, Chemistry

Phi Beta Kappa Elects 51 Division of Science Students

Phi_Beta_Kappa_KeyThe Brandeis chapter of Phi Beta Kappa recently elected 97 new members. Of the 97, at least 51 undergraduate students are majors in the Division of Science (Biochemistry, Biological Physics, Biology, Chemistry, Computer Science, Mathematics, Neuroscience, Physics and Psychology).

Congratulations to the following new Phi Beta Kappa members from the Division of Science:

Biochemistry

Malia Barbra McAvoy
Yehonatan Otzar Meschede-Krasa
Juhee Park
Lior Rozhansky
Hanchen Zhao (double major with Chemistry)

Biological Physics

Abigail Rose Knecht

Biology

Ignatius Ang
Zachary Ian Fried
Jenna Leah Kahane
Ariel Jennifer Katz
Yang Li
Yixuan Liao
Alice Yuan Meng
Khang Vi Nguyen (double major with Chemistry)
Danielle Marie Quintin
Sarah Shin

Chemistry

Khang Vi Nguyen (double major with Biology)
Soobyung Park
Noam Isaac Saper
Hanchen Zhao (double major with Biochemistry)

Computer Science

Kenneth William Foner
Huy Quang Mai
Grady Berry Ward (double major in Mathematics)

Mathematics

Cameron Zhang Fen
Trevor Weiss Kafka
Linda Li
Huy Quang Mai
Stefan Stanojevic
Zhengyang Zhou
Daniel Jackson Kutner (double major in Physics)
Murielle Claire Tugendhaft
Grady Berry Ward (double major in Computer Science)

Neuroscience

Jessica Allison Haley (double major with Psychology)
Kiera Gillian Sarill (double major with Psychology)

 

Physics

Wei Zhong Goh
Stefan Stanojevic
Daniel Jackson Kutner

Psychology

Kyra Jordana Borenstein
Hannah Dvorah Caldwell
Nicole Danielle Cardona
Avi David Cohen
Annie Cui
Jason Michael Desimone
Emily Rose Friedman
Jonathan David Gilman
Clara Emily Gray
Cecilie Gromada
Sarah Jessica Hack-Chabot
Jessica Allison Haley (double major with Neuroscience)
Jessica Lynn Lieberman
Danielle Mizrachi
Emily April Mostow
Linda Sue Nakagawa
Talia Michelle Portal
Jenna Louise Rice
Kiera Gillian Sarill (double major with Neuroscience)
Aliza Naomi Shapiro

See full story on BrandeisNow.

Physics students win awards

The Physics Department recently held its annual Student Research Symposium in Memory of Professor Stephan Berko. At the symposium, the undergraduate speakers describe their senior thesis honors research as the final step in gaining an honors degree in physics. The graduate student speakers are in the middle of their PhD research, and describe their progress and goals.

The prize winners are nominated and chosen by the faculty for making particularly noteworthy progress in their research. Here are the Berko prize winners for 2015:

Undergraduate Prize Winners:

Adam Wang
Title: “Controlling Coupled Chemical Oscillators: Toward Synchronization Engineering and Chemical Computation”
video

Jacob Gold
Title: “Inhibitively Coupled Chemical Oscillators as a Substrate for Logic Gates and Larger Circuits”
video

Graduate Prize Winners:

Lishibanya Mohapatra
Title: “How cells control the size of their organelles?”
video

Feodor Hilitski
Title: “Measuring mechanics of active microtubule bundles, one filament at a time”
video

Other Physics Prize winners this year:

Cesar A. Agon Falkoff prize
Hannah Herde Falkoff prize
Matthew Cambria Physics Faculty prize
Stefan Stanojevic Physics Faculty prize

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