People-The McWilliams Center for Cosmology - Carnegie Mellon University

Carnegie Mellon Faculty in the McWilliams Center

Guy Blelloch

Professor, Computer Science

Guy Blelloch works on parallel algorithms and programming languages. In the area of algorithms, he has worked on algorithms for a variety of problems including meshing, n-body codes, sorting, computational biology, graph problems, and compact data representations. In the area of programming languages, he has worked on developing new language structures for parallelism and techniques for efficiently executing parallel codes.

Personal web page:
http://www.cs.cmu.edu/~guyb/

Roy Briere

Professor, Physics

Roy Briere concentrates on precision measurements in weak flavor physics as a means for searching for new physics beyond the current Standard Model.  This method is complementary to direct searches for new particles at energy frontier machines.  The weak interactions of quarks are currently the only known source of matter-antimatter (CP) symmetry violation, but the preponderance of matter over antimatter in our universe tells us that there must be an additional source of CP violation that is as yet undiscovered.  He recently joined the BelleII Collaboration, which will continue the search for new CP-violating phenomena.

Personal web page
info.phys.cmu.edu/people/faculty/briere/

Rupert Croft

Professor, Physics

Rupert Croft’s main research interests are in computational cosmology, involving both simulations and the analysis of data from large surveys. He primarily focuses on the physics of the intergalactic medium, its use as a probe of cosmology and of galaxy and quasar formation. He is participating in the SDSS-III and SDSS-IV surveys of galaxies and quasar absorption lines which have measured and will measure dark energy parameters using large scale baryonic oscillatory features as a standard ruler. Croft also works on the interaction between matter and radiation in the intergalactic medium, on the re-ionization of the Universe, and on new cosmological probes of modified gravity, such as gravitational redshifts of galaxies. He makes use of the McWilliams Center’s high performance computing facilities, including the Warp and Coma clusters to perform cosmological hydrodynamic and radiative transfer simulations.

Personal web page:
http://www.cmu.edu/physics/people/faculty/croft.html

Tiziana Di Matteo

Associate Professor, Physics

Tiziana is a theorist with expertise in both high energy astrophysics and cosmology. Her recent interests focus on state-of-the-art cosmological simulations of galaxy formation including detailed modeling of the impact of black hold feedback on structure formation. She has consistently been awarded large allocations of time on the largest national computing facilities and also makes use of the computational facilities of the McWilliams Center for Cosmology.

Personal web page:
http://www.cmu.edu/physics/people/faculty/dimatteo.html

Christos Faloutsos

Professor, Computer Science

Christos Faloutsos works on data mining for large datasets. He has been using the idea of fractal dimension to characterize clouds of points in n-dimensional space, the 'hadoop'/mapReduce architecture to handle large datasets, and spectral methods to analyze large graphs.

Personal web page:
http://www.cs.cmu.edu/~christos/

Peter Freeman

Project Scientist, Statistics

Peter Freeman's main research interest is the application of advanced statistical methods to astronomical data.  Some of his recent work includes using nonparametric methods to estimate the foreground in CMB observations; using non-linear data transformation techniques to estimate photometric redshifts; and advancing source detection techniques in anticipation of LSST.

Personal web page:
http://www.stat.cmu.edu/~pfreeman

Christopher Genovese

Professor, Statistics

Christopher Genovese's research involves high-dimensional and nonparametric inferences with applications to complex scientific problems. A major focus of his research is developing statistical methods for problems in astrophysics and cosmology, including analysis of the Cosmic Microwave Background, inference for the dark energy equation of state, and source detection.

Personal web page:
http://www.stat.cmu.edu/~genovese

Garth Gibson

Professor, Computer Science

Garth Gibson's research centers on large data processing and storage systems such as the world's largest parallel and distributed file systems for supercomputing and internet services. He leads a team that is exploring alternative parallel analysis computing models for large clusters (such as MapReduce) and applying these tools to astrophysics datasets that are terabytes to petabytes in size, and billions of particles in complexity.

Personal web page:
http://www.cs.cmu.edu/~garth

Fred Gilman

Dean, Mellon College of Science
Professor, Physics

Fred Gilman’s research is in theoretical particle physics, particularly in understanding the nature of CP violation. Additional sources of CP violation outside the Standard Model are required to explain the dominance of matter over antimatter in the universe. Together with dark matter, dark energy, and the field(s) responsible for inflation, these four fundamental particle physics issues all point to physics beyond the Standard Model. Gilman is Director of the McWilliams Center for Cosmology.  He is a member of LSST Dark Energy Science Collaboration and is on its Executive Board.  Gilman serves on the Board of the Large Synoptic Survey Telescope Corporation, is Chair of the AURA Management Council for the LSST (AMCL) that oversees the project to construct, commission, and operate the LSST, and is a member of the Board of Directors of AURA.

Personal web page:

www.cmu.edu/people/physics/people/faculty/gilman.html

Shirley Ho

Assistant Professor, Physics

Shirley Ho is a cosmologist whose interest ranges from theory to observations, and whose research involves both simulations and analyses of large scale structure via novel techniques developed in Machine Learning and Statistics. Utilizing large scale structure and the cosmic microwave background, she seeks to understand the beginning of the Universe and its evolution, its dark components (dark energy and dark matter), and the light, elusive neutrinos. Her recent research focuses on the use of a standard ruler called Baryon Acoustic Oscillations via various large scale structure tracers such as the 3D clustering. In this way, she plays leading roles in large scale structure analyses in the SDSS-III, SDSS-IV, and Large Synoptic Sky Telescope collaborations (in particular, within the LSST Dark Energy Science Collaboration). In addition, she is a member of the future Dark Energy Spectroscopic Instrument (DESI) and Euclid surveys.

Personal web site:

http://www.cmu.edu/physics/people/faculty/ho.html

Richard Holman

Professor, Physics

Rich Holman's research focuses mainly on early universe physics. In particular, the quantum field theory involved in understanding the inflationary paradigm has been at the forefront of his research program. His current work deals with how to use possible observations of non-gaussianity in the CMB to constrain the quantum vacuum the inflaton field. He is also interested in other aspects of astroparticle physics, such as how notions such as the landscape of string theory might be tested via observations of large scale structure.

Personal web page:

http://www.cmu.edu/physics/people/faculty/holman.html

Tina Kahniashvili

Associate Research Professor, Physics

Tina Kahniashvili's research interests are in theoretical cosmology and astrophysics. Her research topics include testing physical processes in the early universe using cosmological and high energy astrophysical data (cosmic microwave background radiation, large scale structure, gamma ray bursts, blazars), modified theories of general relativity (in particular, massive gravity), the gravitational wave signal arising from inflation and cosmological phase transitions, dark energy-dark matter interacting cosmological models, primordial magnetic fields and their signatures, and magneto-hydrodynamic turbulence in astrophysical plasmas.

Leonard Kisslinger

Professor (emeritus), Physics

Leonard Kisslinger's astrophysics research is in the general area of astroparticle physics. Much of his research is on the electroweak and QCD phase transitions, which occurred when the temperature of the universe was about 100 Gev and 150 MeV, respectively. He has been investigating the magnetic fields which are produced for possible polarization correlations in the CMB radiation and as seeds for the galactic and extragalactic magnetic fields which have been observed. Recently, in collaboration with Professor Tina Kahniashvili, he has worked on the gravitational waves produced by these phase transitions. Also, in collaboration with experimentalists and theorists at LANL, he has been studying the detection of quark/gluon plasma in RHIC experiments and the very large velocities of pulsars that are produced in a supernova collapse.

Personal web page:

http://www.cmu.edu/physics/people/faculty/kisslinger.html

Rachel Mandelbaum

Assistant Professor, Physics

Rachel Mandelbaum's research interests are predominantly in the areas of observational cosmology and galaxy studies.  This work includes the use of weak gravitational lensing and other analysis techniques, with projects that range from development of improved data analysis methods, to actual application of such methods to existing data.  Currently, she is focusing on data from the SDSS (including the ongoing SDSS-III), and is working on upcoming surveys including Hyper-SuprimeCam (HSC) and LSST.

Personal web page:

http://www.andrew.cmu.edu/user/rmandelb/

Manfred Paulini

Professor, Physics

Manfred Paulini studies questions connecting particle physics to issues relevant for cosmology. One such question is the predominance of matter over antimatter in the universe, which requires a breaking of the CP symmetry between matter and antimatter in particle physics. As a member of the CDF experiment at Fermilab, Paulini studied the violation of CP symmetry and matter-antimatter oscillations in neutral Bs mesons. Another question concerns the nature of dark matter that makes up about one quarter of the content of the universe. Paulini searches for the production of dark matter particles with the CMS experiment at the Large Hadron Collider at CERN. He analyzes the CMS data looking for supersymmetric particles with decay chains that involve photons in the final state.

Personal web page:

http://www.cmu.edu/physics/people/faculty/paulini.html

Jeffrey Peterson

Professor, Physics

Jeff Peterson's group carries out cosmological observations using the 21 cm emission line of neutral hydrogen. The group is involved in projects using existing telescopes to make three dimensional maps of 21 cm emission for redshifts around ten. These maps will be used to study the first stars and their interaction with surrounding gas. The team also designs and builds 21 cm telescopes. In particular, the group is working to build the Cylinder Radio Telescope in Morocco. This 10,000 square meter telescope will map most of the sky at redshifts near one in order to constrain models of Dark Energy.

Personal web page:
http://www.cmu.edu/physics/people/faculty/peterson.html

Ira Rothstein

Professor, Physics

Ira Rothstein works on diverse topics in quantum field theory and general relativity.  He focuses on developing field theoretic tools for the purpose of increasing predictive power in complex non-linear field theories, such as QCD and gravity.  In the past, he has been particularly interested in developing effective field theory techniques in order to search for new physics in the Yukawa sector of the standard model.  Presently he has been concentrating on a recent formalism (NRGR) developed to study binary inspirals and using NRGR to calculate higher order post-Newtonian corrections to these systems for the purpose of building gravity wave templates for LIGO and LISA.  As with the rest of the particle physics community, he is anxiously awaiting the results from the LHC.  The advent of data collection will be a very exciting time, hopefully with the discovery of new physics that will explain the dark matter as well as the hierarchy problem.  Until then, he plans to work on finding methods to search for new physics in the model independent ways.  In particular, he is interested in understanding how to determine at early stages of LHC running if we have produced new particles but have not been able to extract them from the background.

Personal web page:
http://www.cmu.edu/physics/people/faculty/rothstein.html

James Russ

Professor, Physics

James Russ is a particle experimentalist whose work impacts the physics goals of the McWilliams Center through his involvement with the CMS experiment at the Large Hadron Collider and his work on neutrino astronomy as a probe of Active Galactic Nuclei (AGN) over different red-shift ranges. At CMS we have an opportunity to discover evidence of extra dimensions and indications of a brane-world, which would revolutionize cosmology. The neutrino astronomy project offers insight into nature's highest-energy particle sources and is one of the few ways to put experimental limits on models of AGN physics.

Personal web page:
http://www.cmu.edu/physics/people/faculty/russ.html

Chad Schafer

Assistant Professor, Statistics

Chad Schafer's work focuses on addressing estimation problems in the sciences using novel, often computationally-intensive, statistical methods.  Projects in astronomy and cosmology have included the development of methods for constructing optimally precise confidence regions for cosmological parameters, for estimating bivariate luminosity functions, and for estimating properties of galaxies via low-dimensional representations of their emission spectra. Recent work has focused on the development of formal statistical estimation procedures that can take advantage of modern cosmological simulation models.

Personal web page:
http://www.stat.cmu.edu/~cschafer

Jeff Schneider

Associate Research Professor, Robotics Institute

Jeff Schneider is pursuing active learning for scientific discovery.  An active learning algorithm not only learns models from data, but also selects which experiments to run in order to collect the training data.  Recent work focused on algorithms that select cosmological parameters for CMBFast runs in order to find those consistent with the WMAP data (Bryan et al., ApJ, 2007).  This work has been extended to selecting across multiple model/data types (e.g., CMB, supernovae, large scale structure) with varying computational costs (Bryan and Schneider, ICML, 2008).  Other current efforts include approaching anomaly detection as an active learning problem and learning dynamic models from static data.

Personal web page:
http://www.cs.cmu.edu/~schneide

Hy Trac

Assistant Professor, Physics

Hy Trac is a theoretical and computational cosmologist whose scientific interests include cosmic evolution and structure formation. He is actively working on understanding how the first generation of stars and galaxies re-ionize the universe and how the intergalactic medium can be studied using the Lyman alpha forest. As a member of the Atacama Cosmology Telescope (ACT) project, he is studying how galaxy clusters can be discovered through the Sunyaev-Zel'dovich effect. His research also focuses on the development and application of N-body, hydrodynamic, and radiative transfer algorithms.

Adrien Treuille

Assistant Professor, Computer Science

Adriene Treuille's research attempts to advance our understanding of very high-dimensional nonlinear phenomena. One thread of his research addresses the complexity of such systems by developing model reduction tools that generate compact representations. A complimentary thread seeks to control such systems. The mathematical techniques that he has developed have been applied to phenomena as diverse as animal morphology, human motion, and large fluid systems.

Personal web page:
http://www.cs.cmu.edu/~treuille/

Helmut Vogel

Professor, Physics

Helmut Vogel's main research interests are in high-energy particle physics experiments. For many years, he worked at LEP, the electron-positron colliding-beam accelerator which was the precursor to the LHC at CERN. Among its landmark results were a determination of the number of neutrino families in the universe and the most stringent lower limit to date on the mass of the Higgs boson. Presently, Vogel is a member of the CMS experiment at the LHC where he plans to study muons produced in the proton-proton collisions as probes of both "conventional" and "exotic" physics processes.

Personal web page:
http://www.cmu.edu/physics/people/faculty/vogel.html

Matthew Walker

Assistant Professor, Physics

Matthew Walker studies the astrophysical properties of dark matter, thus far via optical imaging, spectroscopy, and dynamical modeling of the "dwarf" galaxies that surround the Milky Way. By measuring the small-scale clustering of dark matter, Walker aims to help figure out what the dark matter is. For this work he uses some of the world's largest optical telescopes, including the 6.5 meter Magellan telescopes at Las Campanas Observatory in Chile, the 6.5 meter MMT at Mt. Hopkins, Arizona, and the 8.2 meter Very Large Telescope at Cerro Paranal in Chile. He is also engaged in the Sloan Digital Sky Survey IV.

Personal web page:

www.cmu.edu/physics/people/faculty/walker.html

Larry Wasserman

Professor, Statistics and Machine Learning

Larry Wasserman's research interests include nonparametric interference, high-dimensional models, and the development of statistical methods for astrophysics problems such as: estimating the equation of state of dark energy; the analysis of the cosmic microwave background radiation; and filament finding.

Personal web page:
http://www.stat.cmu.edu/~larry

Postdoctoral Fellows

Nishant Agarwal

McWilliams Postdoctoral Fellow, Physics

Nishant Agarwal is a theoretical cosmologist who is interested in studying and developing models for the evolution of the Universe. His main areas of research are the past (inflation) and present (dark energy) acceleration of the Universe.  He studies different models of inflation, such as scalar field models and brane inflation, in the light of current observations. In the area of dark energy, his research focuses on theories based on large-scale modifications to gravity, such as scalar-tensor gravity, braneworld scenarios, and massive gravity. He is also interested in the astrophysical consequences of pseudoscalar-photon mixing, particularly on the polarization of CMB radiation and optical radiation from distant quasars.

Nicholas Battaglia

McWilliams Postdoctoral Fellow, Physics

Nick Battaglia works on cosmology and large-scale structure, focusing on galaxy clusters, the largest gravitationally bound objects in the Universe.  He is currently involved in characterizing and simulating in large cosmological boxes the detailed physical processes of the intra-cluster medium, such as energetic feedback from active galactic nuclei and non-thermal pressure support. These processes contribute significantly to the overall energy budget of clusters and must be included in the interpretation of the latest high resolution cosmic microwave background observations from the Planck satellite, the Atacama Cosmology Telescope, and the South Pole Telescope.

Dustin Lang

McWilliams Postdoctoral Fellow, Physics

Dustin Lang is a computer scientist by training, who is interested in principled statistical data analysis problems in large astronomical surveys.  In particular, he works on designing algorithms for making pixel-level measurements of stars and galaxies in tera-pixel (and upcoming peta-pixel) imaging collections, and connecting these measurements to higher-level scientific analyses.  Weak gravitational lensing, a key cosmological probe, is one of the most challenging measurements and motivates much of this work.  He works on projects and data including the Sloan Digital Sky Survey, Hyper-Suprime Cam, the Large Synoptic Survey Telescope, the Canada-France-Hawaii Telescope, BigBOSS, and the Hubble Space Telescope.

Mariana Vargas-Magaña

Postdoctoral Fellow, Physics

Mariana Vargas-Magaña is an observational cosmologist who is interested in the large scale structure of the universe and the observational probes designed to understand dark energy.  She is currently involved in the BOSS collaboration, with her research focus on baryonic acoustic oscillations using luminous galaxies and, more recently, using the Lyman-alpha forest as a tracer of the matter.  She is currently working on developing an improved reconstruction algorithm to recover the BAO feature erased by the non-linear evolution of density.

KwangHo Park

Urania-Stott Postdoctoral Fellow

KwangHo Park is a theoretical astrophysicist whose research interest is the growth and evolution of the first black holes formed from Population  III stars in the early universe. He applies sub-grid scale radiation-hydrodynamic simulations of radiation-regulated accretion onto black holes to cosmological simulations. The effect of high energy emission of radiation from the black holes on the large-scale environment is also one of the main questions that could be answered.

Personal web page:
http://www.andrew.cmu.edu/user/kwanghop

Melanie Simet

Postdoctoral Fellow, Physics

Melanie Simet works on weak gravitational lensing, especially its applications to cosmology and galaxy cluster studies. She uses cosmological surveys to investigate the large-scale structure of matter (with tools such as cosmic shear and galaxy clustering) and to statistically probe smaller features such as the mass and concentration of cluster-sized dark matter haloes. Her research also involves related technical issues such as the calibration of photometric redshifts for upcoming surveys and the characterization of systematic errors from both measurement and theory.

Personal web page:
http://www.andrew.cmu.edu/user/msimet

Ying Zu

Postdoctoral Fellow, Physics

Ying Zu is an observation-oriented theoretical astrophysicist who works on a broad range of topics including galaxy clusters, weak gravitational lensing, and supermassive blackholes. He is currently developing novel schemes to probe dark energy using the growth of cosmic structures from galaxy surveys and to study the link between galaxies and dark matter halos in the universe.