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Niayesh Afshordi

Portrait de Niayesh Afshordi
University of Waterloo - Department of Physics and Astronomy

Areas of Research:
Email: nafshordi@perimeterinstitute.ca
Phone: x6532

I am an Astronomer, and a Physicist; in short I am an astrophysicist. I am an Assistant Professor in the Astrophysics and Gravitation group at the Department of Physics and Astronomy University of Waterloo. I am also an Associate Faculty in the Cosmology group at the Perimeter Institute for Theoretical Physic (PI). I dabble in Astrophysics, Cosmology, and Physics of gravity. I am obsessed with observational hints that could help address problems in fundamental physics. In particular, I have found anomalous signatures of dark energy and dark baryons in the cosmic microwave background radiation. With other collaborators, I have also developed a curious theory for an incompressible dark energy, named cuscuton (after the Latin name for the parasitic plant of dodder). I am currently trying my hand in solving the cosmological constant problem through a new theory of gravity that can surprisingly relate the formation of astrophysical black holes to today's acceleration of cosmic expansion. In a related inquiry, I am also exploring the relation of cuscuton and quantum gravity.

Research Interests

Astrophysics, Cosmology, Physics of Gravity, Dark Energy, Dark Matter, Clusters of Galaxies, Structure Formation, Accretion Disks, Cosmic Microwave Background, Missing Baryons, Quantum Field Theory, Quantum Gravity, Lorentz Violation, Black Holes, Neutron Stars, Early Universe, Primordial Magnetic Field, Foundations of Quantum Mechanics

Positions Held

  • 2007-2009 Perimeter Institute for Theoretical Physics Distinguished Research Fellow
  • 2004 - 2007 Institute for Theory and Computation (ITC), Harvard College Observatory, Harvard University ITC Postdoctoral Fellow
  • 2000 - 2004 Department of Astrophysical Sciences, Princeton University Graduate Student


  • Early Researcher Award, Ministry of Research and Innovation, Province of Ontario, Canada
  • Professor M. K. Vainu Bappu Gold Medal 2008, Astronomical Society of India (jointly with Nissim Kanekar)
  • Discovery Accelerator Supplement, Natural Sciences and Engineering Research Council of Canada (NSERC), 2010 (8 awarded across Canada in Physics)
  • Distinguished Research Fellowship, Perimeter Institute for Theoretical Physics, Waterloo, Canada

Recent Publications

  • Thermal Tachyacoustic Cosmology, Abhineet Agarwal (Waterloo), Niayesh Afshordi (Perimeter/Waterloo), Phys. Rev. D 90 (2014), 043528, arXiv: 1406.0575
  • How does pressure gravitate? Cosmological constant problem confronts observational cosmology, Ali Narimani, Niayesh Afshordi, Douglas Scott, JCAP, 08 (2014) 049, arXiv: 1406.0479
  • Elcio Abdalla, Niayesh Afshordi, Michele Fontanini, Daniel C. Guariento, Eleftherios Papantonopoulos, Cosmological black holes from self-gravitating fields, Phys. Rev. D 89, 104018 (2014), arXiv: 1312.3682
  • Jesus Zavala (1,2,3,4), Niayesh Afshordi (1,2) ((1) PI, (2) UW, (3) CITA, (4) Dark Cosmology Centre), Clustering in the Phase Space of Dark Matter Haloes. II. Stable Clustering and Dark Matter Annihilation, Monthly Notices of the Royal Astronomical Society, 2014, Volume 441, Issue 2, p.1329-1339, arXiv: 1311.3296
  • Mehdi Saravani, Niayesh Afshordi, Robert B. Mann, Dynamical Emergence of Universal Horizons during the formation of Black Holes, Phys. Rev. D 89, 084029 (2014), arXiv: 1310.4143
  • Transient Weak-Lensing by Cosmological Dark Matter Microhaloes, Sohrab Rahvar, Shant Baghram, Niayesh Afshordi,Phys Rev D 89 (2014), 063001, arXiv: 1310.5412
  • Out of the White Hole: A Holographic Origin for the Big Bang, R. Pourhasan, N. Afshordi and R.B.Mann, JCAP, 04 (2014) 005, arXiv: 1309.1487
  • Clustering in the Phase Space of Dark Matter Haloes. I. Results from the Aquarius simulations, J.Zavala and N.Afshordi, Monthly Notices of the Royal Astronomical Society, 2014, Volume 441, Issue 2, p.1317-1328, arXiv: 1308.1098
  • An Optimal and Model-Independent Measurement of the Intracluster Pressure Profile I: Methodology and First Applications, Siavash Aslanbeigi, Guilhem Lavaux, Amir Hajian, Niayesh Afshordi, Monthly Notices of the Royal Astronomical Society, 2013, Volume 435, Issue 2, p.1788-1808, arXiv: 1304.6457
  • Removal and mixing of the coronal gas from satellites in galaxy groups: cooling the intragoup gas, Jesus Zavala, Michael L. Balogh, Niayesh Afshordi, Stephen Ro, Mon.Not.Roy.Astron.Soc.,426, 3464, arXiv: 1208.4849 [astro-ph.CO]
  • A Ground State for the Causal Diamond in 2 Dimensions, Niayesh Afshordi, Michel Buck, Fay Dowker, David Rideout, Rafael D. Sorkin, Yasaman K. Yazdi, JHEP, 1210, 088, arxiv:hep-th/1207.7101
  • First measurement of the bulk flow of nearby galaxies using the cosmic microwave background. By Guilhem Lavaux, Niayesh Afshordi, Michael J. Hudson, Mon. Not. Roy. Astron. Soc. 430, 1617 [arXiv: 1207.1721 [astro-ph.CO]].
  • A Distinguished Vacuum State for a Quantum Field in a Curved Spacetime: Formalism, Features, and Cosmology, Niayesh Afshordi, Siavash Aslanbeigi, Rafael D. Sorkin, JHEP 1208 (2012) 137, arxiv:hep-th/1205.1296
  • Chameleon Gravity, Electrostatics, and Kinematics in the Outer Galaxy. By R. Pourhasan, N. Afshordi, R.B. Mann, A.C. Davis. [arXiv: 1109.0538 [astro-ph.CO]]. JCAP 1112 (2011) 005.
  • Phenomenology of Gravitational Aether as a solution to the Old Cosmological Constant Problem. By Siavash Aslanbeigi, Georg Robbers, Brendan Z. Foster, Kazunori Kohri, Niayesh Afshordi. [arXiv: 1106.3955 [astro-ph.CO]]. Phys.Rev. D84 (2011) 103522.
  • Neutron Stars and the Cosmological Constant Problem. By Farbod Kamiab, Niayesh Afshordi. [arXiv: 1104.5704 [astro-ph.CO]]. Phys.Rev. D84 (2011) 063011.
  • Prospects for Detecting Dark Matter Halo Substructure with Pulsar Timing, Shant Baghram, Niayesh Afshordi, Kathryn M. Zurek, Physical Review D, vol. 84, Issue 4, id. 043511, arXiv: 1101.5487v2 [astro-ph.CO]
  • Niayesh Afshordi, Anze Slosar, Yi Wang, A Theory of a Spot, JCAP 1101:019,2011, arXiv: 1006.5021
  • Niayesh Afshordi, Roya Mohayaee, Edmund Bertschinger, Hierarchy in the Phase Space and Dark Matter Astronomy, Phys.Rev. D81 (2010) 10130, arXiv:astro-ph.CO/0911.0414
  • Niayesh Afshordi, Reviving Gravity's Aether in Einstein's Universe, Physics in Canada (2010) 66.2, arXiv:physics.pop-ph/1004.2901
  • Niayesh Afshordi (Perimeter Institute), Cuscuton and low energy limit of Horava-Lifshitz gravity, Phys.Rev. D80 (2009) 081502, arxiv:hep-th/0907.5201
  • Chanda Prescod-Weinstein (Perimeter Institute/U-Waterloo), Niayesh Afshordi (Perimeter Institute), Michael L. Balogh (U-Waterloo), Stellar Black Holes and the Origin of Cosmic Acceleration, Phys. Rev. D 80, 043513 (2009), arxiv:astro-ph.CO/0905.3551
  • Niayesh Afshordi, Ghazal Geshnizjani, Justin Khoury (Perimeter Institute), Observational Evidence for Cosmological-Scale Extra Dimensions, JCAP 08 (2009) 030, arXiv: 0812.2244
  • Niayesh Afshordi (Perimeter Institute), Roya Mohayaee (IAP), Edmund Bertschinger (MIT), Hierarchical Phase Space Structure of Dark Matter Haloes: Tidal debris, Caustics, and Dark Matter annihilation, Phys. Rev. D 79, 083526 (2009), arxiv:astro-ph/0811.1582
  • Marilena LoVerde, Niayesh Afshordi, Extended Limber Approximation, Phys.Rev.D78:123506,2008, arxiv:astro-ph/0809.5112
  • Niayesh Afshordi, Andrew J. Tolley (Perimeter Institute), Primordial non-gaussianity, statistics of collapsed objects, and the Integrated Sachs-Wolfe effect, Phys.Rev.D78:123507,2008, arxiv:astro-ph/0806.1046
  • Georg Robbers, Niayesh Afshordi, Michael Doran, Does Planck mass run on the cosmological horizon scale?, Phys.Rev.Lett.100:111101,2008, arXiv: 0708.3235
  • Niayesh Afshordi (Perimeter/Harvard), Fundamental Plane of Sunyaev-Zeldovich clusters, Astrophys.J. 686 (2008) 201-205, arXiv: 0704.2416
  • Niayesh Afshordi (ITC, Harvard), Daniel J.H. Chung (UW-Madison), Michael Doran (Heidelberg), Ghazal Geshnizjani (UW-Madison), Cuscuton Cosmology: Dark Energy meets Modified Gravity, Phys.Rev.D75:123509,2007, arXiv: astro-ph/0702002
  • Niayesh Afshordi (ITC, Harvard), Yen-Ting Lin (Princeton/Catolica), Daisuke Nagai (CalTech), Alastair J. R. Sanderson (Birmingham), Missing Thermal Energy of the Intracluster Medium, Mon.Not.Roy.Astron.Soc.378:293-300,2007, arXiv: astro-ph/0612700
  • Niayesh Afshordi (ITC, Harvard), How well can (renormalized) perturbation theory predict dark matter clustering properties?, Phys.Rev.D75:021302,2007, arXiv: astro-ph/0610336
  • Niayesh Afshordi (ITC, Harvard), Daniel J.H. Chung, Ghazal Geshnizjani (UW-Madison), Cuscuton: A Causal Field Theory with an Infinite Speed of Sound, Phys.Rev.D75:083513,2007, arXiv: hep-th/0609150
  • Niayesh Afshordi (Harvard College Observatory), Intracluster Medium through three years of WMAP, NewAstron.Rev.50:905-908,2006, arXiv: astro-ph/0608503
  • Niayesh Afshordi, Matias Zaldarriaga (Harvard), Kazunori Kohri (Harvard/Osaka), On the stability of Dark Energy with Mass-Varying Neutrinos, Phys.Rev. D72 (2005) 065024, arXiv: astro-ph/0506663
  • Ghazal Geshnizjani, Daniel J.H. Chung (UW-Madison), Niayesh Afshordi (Harvard), Do Large-Scale Inhomogeneities Explain Away Dark Energy?, Phys.Rev. D72 (2005) 023517, arXiv: astro-ph/0503553
  • Christopher M. Hirata, Abraham Loeb, Niayesh Afshordi, CMB B-mode polarization from Thomson scattering in the local universe, Phys.Rev. D71 (2005) 063531, arXiv: astro-ph/0501167
  • Banibrata Mukhopadhyay, Niayesh Afshordi, Ramesh Narayan (Harvard), Bypass to Turbulence in Hydrodynamic Accretion Disks: An Eigenvalue Approach, Astrophys.J. 629 (2005) 383-396, arXiv: astro-ph/0412193
  • Niayesh Afshordi, Banibrata Mukhopadhyay, Ramesh Narayan (ITC/Harvard), Bypass to Turbulence in Hydrodynamic Accretion: Lagrangian Analysis of Energy Growth, Astrophys.J. 629 (2005) 373-382, arXiv: astro-ph/0412194
  • Niayesh Afshordi (Harvard/Princeton), Yen-Ting Lin (Illinois), Alastair J.R. Sanderson (Illinois/Birmingham), WMAP constraints on the Intra-Cluster Medium, Astrophys.J. 629 (2005) 1-14, arXiv: astro-ph/0408560
  • Ghazal Geshnizjani, Niayesh Afshordi, Coarse-Grained Back Reaction in Single Scalar Field Driven Inflation, JCAP 0501 (2005) 011, arXiv: gr-qc/0405117
  • Niayesh Afshordi (Princeton University Observatory), Integrated Sachs-Wolfe effect in Cross-Correlation: The Observer's Manual, Phys.Rev. D70 (2004) 083536, arXiv: astro-ph/0401166
  • Niayesh Afshordi, Yeong-Shang Loh, Michael A. Strauss (Princeton University Observatory), Cross-Correlation of the Cosmic Microwave Background with the 2MASS Galaxy Survey: Signatures of Dark Energy, Hot Gas, and Point Sources, Phys.Rev. D69 (2004) 083524, arXiv: astro-ph/0308260
  • N. Afshordi, P. McDonald, D.N. Spergel, Primordial Black Holes as Dark Matter: The Power Spectrum and Evaporation of Early Structures, Astrophys.J. 594 (2003) L71-L74, arXiv: astro-ph/0302035
  • Horndeski meets McVittie: A scalar field theory for accretion onto cosmological black holes, Niayesh Afshordi, Michele Fontanini, Daniel C. Guariento, arXiv: 1408.5538
  • Schwinger Effect in 4D de Sitter Space and Constraints on Magnetogenesis in the Early Universe, Takeshi Kobayashi, Niayesh Afshordi, arXiv: 1408.4141
  • A Non-Local Reality: Is there a Phase Uncertainty in Quantum Mechanics?, Elizabeth S. Gould, Niayesh Afshordi (Perimeter/Waterloo), arXiv: 1407.4083
  • Emergent Spacetime in Stochastically Evolving Dimensions, Niayesh Afshordi, Dejan Stojkovic, arXiv: 1405.3297
  • Empty Black Holes, Firewalls, and the Origin of Bekenstein-Hawking Entropy, M.Saravani, N.Afshordi and R.B.Mann [arXiv: 1212.4176 [hep-th]]
  • Lithium Diffusion in the Post-Recombination Universe and Spatial Variation of [Li/H], Maxim Pospelov, Niayesh Afshordi, arXiv: 1208.0793
  • Where will Einstein fail? Lessons for gravity and cosmology. By Niayesh Afshordi. [arXiv: 1203.3827 [astro-ph.CO]].
  • Using Dark Matter Haloes to Learn about Cosmic Acceleration: A New Proposal for a Universal Mass Function, C. Prescod-Weinstein, N. Afshordi, arXiv: 1010.5501v1 [astro-ph.CO]
  • Bruce A. Bassett, Niayesh Afshordi, The Non-Gaussian Sting in Posteriors arising from Marginal Detections, arXiv: 1005.1664 [astro-ph.CO]
  • Niayesh Afshordi, Dark Energy, Black Hole Entropy, and the First Precision Measurement in Quantum Gravity, arXiv: 1003.4811 [hep-th]
  • Niayesh Afshordi (Perimeter Institute), Gravitational Aether and the thermodynamic solution to the cosmological constant problem, arXiv: 0807.2639
  • Physical Evidence for Dark Energy, R. Scranton, A. J. Connolly (UPitt), R. C. Nichol (CMU), A. Stebbins (FNAL), I. Szapudi (Hawaii), D. J. Eisenstein (Steward), N. Afshordi (Princeton), T. Budavari (JHU), I. Csabai (Eotvos), J. A. Frieman (FNAL), J. E. Gunn (Princeton), D. Johnson (CfCP), Y. Loh, R. H. Lupton (Princeton), C. J. Miller (CMU), E. S. Sheldon (CfCP), R. S. Sheth (UPitt), A. S. Szalay (JHU), M. Tegmark, Y. Xu (UPenn), et al. (SDSS collaboration), arXiv: astro-ph/0307335
  • Niayesh Afshordi, Robert C. Mann, Razieh Pourhasan, The Black Hole at the Beginning of Time, Scientific American (August 2014)
  • Jesus Zavala, Niayesh Afshordi, P2SAD: Particle Phase Space Average Density, Astrophysics Source Code Library, record ascl:1402.030


  • "Probing Dark Matter Nanostructure", Mitchell Workshop on Collider and Dark Matter Physics, United States, Texas, College Station
  • "Tales of Dark Matter on Small Scales", Colloquium - Kavli Institute for Astronomy and Astrophysics, China, Beijing
  • "Missing Baryons: How Much? How Hot? How Fast?", Cross-Correlating Cosmic Fields Conference, China, Shanghai
  • "Out of the White Hole: A Holographic Origin for the Big Bang" Invited Contribution, Cosmology After Planck, University of Michigan-Ann Arbor
  • "Dynamical Emergence of Universal Horizons during the formation of Black Holes" Invited Contribution, LOOPS 13, Perimeter Institute
  • "Where wil Einstein Fail?" Invited Contribution, Canadian Astronomical Society (CASCA) Annual Meeting, University of British Columbia
  • "Life after Lorentz: Quantum Mechanics, Gravity, and the Crisis of Falsi fiability" Invited Colloquium, University of Wisconsin-Madison
  • "Tales of Dark Matter on small scales" Invited Contribution, TAMU Workshop on Dark Matter, Texas A&M University
  • "Why is particle physics Lorentz-Invariant?" -Invited Contribution, Kavli IPMU focus week on Gravity and Lorentz violation
  • "Why is particle physics Lorentz-Invariant?" Invited Contribution, Experimental Search for Quantum Gravity: The Hard Facts, Perimeter Institute
  • "Hot Big Bang at a Lifshitz point" Invited Contribution, Canadian Association of Physicists Congress , Calgary, AB
  • "Tales of Dark Matter on small scales" Invited Contribution, Theoretical Physics Workshop, Western University, London, ON
  • "Reviving Gravity"s Aether in Einstein"s Universe" -Invited Colloquium, York University, Toronto, ON (Feb. 2012)
  • "Horava-Lifshitz Cosmology and Dark Matter Haloes" -Invited Lectures, Cape Town Cosmology School (Jan. 2011)
  • "Where will Einstein fail? Insights into Gravity and Dark Energy" -Vainu Bappu Memorial Gold Medal award ceremony, IUCAA, Pune, India (Oct. 2011) -KICP Colloquium, University of Chicago (Oct. 2011) -Invited Seminar, Canadian Institute for Theoretical Physics (CITA), University of Toronto (Sep. 2011)
  • "Aether, Quantum Gravity and Cosmology" Invited Contribution, Cosmological Frontiers in Fundamental Physics, APC, Paris
  • "Fine Structure of Dark Matter Phase Space" Invited Contribution, Dark Matter: Its Origin, Models, and Detection, University of New Mexico
  • "Aether, Quantum Gravity, and Cosmology" Invited Contribution, Philosophy of Cosmology, University of Western Ontario
  • "How can astrophysical compact objects shed light on dark cosmology?" Invited High Energy Theory Seminar, University of Amsterdam
  • "Largest and Smallest Dark Matter Clusters, and what we can learn from them" Invited High Energy Theory Seminar, University of Michigan, Ann Arbor
  • "Cosmology and the End of Physics!" Invited Colloquium, Physics Department, Guelph University
  • "Non-linear Structure Formation in Cosmology" Invited Lectures, Institute for Research in Fundamental Sciences (IPM), Tehran
  • "First Precision Measurement in Quantum Gravity" High Energy Physics Seminar, Institute for Research in Fundamental Sciences (IPM), Tehran (Aug. 2010)
  • "Hierarchy in the Phase Space and Dark Matter Astronomy" Astrophysics seminar, Queen's University, Kingston, ON
  • "Stellar Black Holes and the Thermodynamic Origin of Cosmic Acceleration" Invited Colloquium, Institut dAstrophysique de Paris
  • "Cuscuton and solving the cosmological constant problem" High Energy Physics seminar, Physics department, Vanderbilt University
  • "Stellar Black Holes and the origin of cosmic acceleration" Cosmology seminar, KIPAC, Stanford University, (Sep. 2009)
  • "Hierarchy in the Phase Space and Dark Matter Astronomy" -CYGNUS 2009 workshop on directional dark matter detection, MIT, Cambridge, MA
  • "Stellar Black Holes and the origin of cosmic acceleration" Theory Canada 5, Fredericton, NB
  • "The End of the Cosmological Constant Problem" -Understanding the Dark Sector: Dark Matter and Dark Energy, Aspen Winter workshop, Aspen, CO
  • "Primordial non-Gaussianity in Cosmology" Cosmology Seminar, Physics department, Sharif University of Technology, Tehran, Iran
  • "Missing thermal energy of the Universe" Invited Contribution, Open questions from clusters of galaxies, OMP, Toulouse, France
  • "Physics beyond the Horizon" Physics Colloquium, University of Pennsylvania
  • "Fundamental Physics with the Integrated Sachs-Wolfe effect" Aspen CMB Conference, Aspen, CO
  • "Fundamental Plane of Sunyaev-Zel'dovich clusters" Astrophysics of near-term Cosmological Observations, CITA, University of Toronto
  • "Our Tumultuous Journey into the Dark Side" Invited Physics Colloquium, York University
  • PIRSA:13090064, A Non-Local Reality: Is there a Phase Uncertainty in Quantum Mechanics?, 2013-09-03, Quantum Foundations
  • PIRSA:13070044, Shape Dynamics - 2, 2013-07-22, Loops 13
  • PIRSA:12100108, Lorentz symmetry: Broken, intact or deformed?, 2012-10-24, Experimental Search for Quantum Gravity 2012
  • PIRSA:12100085, Photons and Quantum Gravity in Astrophysics, 2012-10-22, Experimental Search for Quantum Gravity 2012
  • PIRSA:12070003, Modern Cosmology, 2012-07-09, Cosmology & Gravitation
  • PIRSA:12050066, Trials and Tribulations of Aether, 2012-05-09, Conformal Nature of the Universe
  • PIRSA:11090081, Structure in the Phase Space and Dark Matter Astronomy, 2011-09-23, Unravelling Dark Matter Conference
  • PIRSA:10050059, Cosmological constant problem: rethinking quantum and gravity, 2010-05-22, Laws of Nature: Their Nature and Knowability
  • PIRSA:09120053, Cosmology - Review (PHYS 621) - Lecture 5, 2009-12-04, Perimeter Scholars International
  • PIRSA:09120052, Cosmology - Review (PHYS 621) - Lecture 4, 2009-12-03, Perimeter Scholars International
  • PIRSA:09120051, Cosmology - Review (PHYS 621) - Lecture 3, 2009-12-02, Perimeter Scholars International
  • PIRSA:09120050, Cosmology - Review (PHYS 621) - Lecture 2, 2009-12-01, Perimeter Scholars International
  • PIRSA:09110144, Cosmology - Review (PHYS 621) - Lecture 1, 2009-11-30, Perimeter Scholars International
  • PIRSA:09110058, Cuscuton and Horava-Lifshitz gravity, 2009-11-09, Gravity at a Lifshitz Point
  • PIRSA:09070014, Black hole horizons and the origin of cosmic acceleration, 2009-07-07, Holographic Cosmology Workshop
  • PIRSA:09050088, Gravitational aether as a solution to the CC problem and more!, 2009-05-27, New Prospects for Solving the Cosmological Constant Problem
  • PIRSA:09030036, (Towards) the end of the cosmological constant problem!, 2009-03-19, Cosmology
  • PIRSA:08100062, Observational Evidence for Massive Gravity, 2008-10-23, PI CITA Joint Cosmology Day
  • PIRSA:C08018, Sep.-Dec., 2008, Astrophysics & Cosmology Through Problems, Graduate Course Lecture Series (with Mark Wyman)
  • PIRSA:08060144, Gravitational Aether as a solution to the cosmological constant problem, 2008-06-03, PASCOS 08
  • PIRSA:08030069, Primordial non-Gaussianity, statistics of collapsed objects, and the ISW effect, 2008-03-10, Origins and Observations of Primodial Non-Gaussianity
  • PIRSA:08020040, Physics beyond the Horizon, 2008-02-20, Colloquium
  • PIRSA:08010043, Physics Beyond the Horizon, 2008-01-25, Cosmology