about meabout

quick facts

I am a theoretical and computational physicist, working in gravitation and cosmology. My research is aimed at the most fundamental questions about the universe: what is the mechanism that set the big bang initial conditions? what is the universe composed of? and how will it be changing in the future? I develop innovative mathematical and numerical methods to explain complex phenomena and make quantitative, testable predictions. My work is also highly influenced by observations, so I make a point of interacting with numerous experimental groups.

research

Currently, I am a Senior Research Scientist at New York University and a Principal Investigator of the Simons Initiative New Directions in Cosmology and Gravitational Theory. I moved to NYU from the Max Planck Society, where I was a Lise Meitner group leader and professor of theoretical physics (2019-22). Before that, I held the inaugural John A. Wheeler Fellowship at the Princeton Center for Theoretical Science (2014-7) and spent two years as a Principal Investigator of the Origins of the Universe Initiative at Columbia (2017-8) and Harvard (2018-9).

academic positions

I completed my doctoral dissertation at the Max Planck Institute for Gravitational Physics in 2014. The last two years of my PhD studies, I was supported by prize fellowships that enabled me to conduct research abroad; I was the Fritz Thyssen Fellow at the Harvard-Smithsonian Center for Astrophysics during 2012-3 and spent the academic year 2013-4 at the Physics Department of Princeton University.

education

I wrote another, award-winning PhD thesis at Munich University in 2010, studying philosophical implications of quantum physics. The Philosophy of Science remains an interest. Besides my research in Cosmology, I am actively participating in the dialogue with Philosophy and the Humanities in general.

misc

publicationspublications

journal articles, books, etc.
Selected journal articles:
  • A. Ijjas, P.J. Steinhardt, D. Garfinkle, W.G. Cook. Smoothing and flattening the universe through slow contraction versus inflation, arXiv:2404.00867.
  • A. Ijjas. Slow Contraction and the Weyl Curvature Hypothesis, arXiv:2304.10030.
  • D. Garfinkle, A. Ijjas, P.J. Steinhardt. Initial conditions problem in cosmological inflation revisited, Phys.Lett. B 843 (2023) 138028, arXiv:2304.12150.
  • A. Ijjas. Gauge/frame invariant variables for the numerical relativity study of cosmological spacetimes, JCAP 06 (2023) 061, arXiv:2304.07616.
  • T. Kist, A. Ijjas. The robustness of slow contraction and the shape of the scalar field potential, JCAP 8 (2022) 046, arXiv:2205.01519.
  • C. Andrei, A. Ijjas, P.J. Steinhardt. Rapidly Descending Dark Energy and the End of Cosmic Expansion, PNAS 119 (2022) e2200539119, arXiv:2201.07704.
  • A. Ijjas. Numerical Relativity as a New Tool for Fundamental Cosmology, Physics 2022, 4(1), 301-314, arXiv:2201.03752.
  • A. Ijjas, P.J. Steinhardt. Entropy, Black Holes, and the New Cyclic Universe, Phys.Lett. B824 (2022) 136823, arXiv:2108.07101.
  • A. Ijjas, F. Pretorius, P.J. Steinhardt and D. Garfinkle. Dynamical attractors in contracting spacetimes dominated by kinetically coupled scalar fields, JCAP 12 (2021) 030, arXiv:2109.09768.
  • A. Ijjas, F. Pretorius, P.J. Steinhardt and A.P. Sullivan. The Effects of Multiple Modes and Reduced Symmetry on the Rapidity and Robustness of Slow Contraction, Phys. Lett. B 820 (2021) 136490, arXiv:2104.12293.
  • A. Ijjas, A.P. Sullivan, F. Pretorius, P.J. Steinhardt and W.G. Cook. Ultralocality and Slow Contraction , JCAP 06 (2021) 013, arXiv:2103.00584.
  • A. Ijjas, R. Kolevatov. Sourcing curvature modes with entropy perturbations in non-singular bouncing cosmologies, JCAP 06 (2021) 012, arXiv:2012.08249.
  • A. Ijjas, R. Kolevatov. Nearly scale-invariant curvature modes from entropy perturbations during the graceful exit phase, Phys. Rev. D.103 (2021) L101302, arXiv:2102.03818.
  • A. Ijjas, W.G. Cook, F. Pretorius, P.J. Steinhardt, and E.Y. Davies. Robustness of Slow Contraction to Cosmic Initial Conditions, JCAP 08 (2020) 030, arXiv:2006.04999.
  • W.G. Cook, I.A. Glushchenko, A. Ijjas, F. Pretorius, and P.J. Steinhardt. Supersmoothing through Slow Contraction, Phys. Lett. B 808 (2020) 135690, arXiv:2006.01172.
  • A. Ijjas, P.J. Steinhardt. A new kind of cyclic universe, Phys.Lett. B795 (2019) 666-672, arXiv:1904.08022.
  • A. Ijjas, F. Pretorius, P.J. Steinhardt. Stability and the Gauge Problem in Non-Perturbative Cosmology, JCAP 01 (2019) 015, arXiv:1809.07010.
  • P. Ade et al (including A. Ijjas). The Simons Observatory: Science goals and forecasts , JCAP 02 (2019) 056, arXiv:1808.07445.
  • A. Ijjas, P.J. Steinhardt. Bouncing Cosmology made simple, Class. Quantum Grav. 35 (2018) 135004, as ‘editor’s suggestion,’ arXiv:1803.01961.
  • A. Ijjas. Space-time slicing in Horndeski theories and its implications for non-singular bouncing solutions, JCAP 02 (2018) 007, arXiv:1710.05990.
  • A. Ijjas. Cyclic completion of the anamorphic universe, Class. Quantum Grav. 35 (2018) 075010, arXiv:1610.02752.
  • A. Ijjas, P.J. Steinhardt. Fully stable cosmological solutions with a non-singular classical bounce, Phys.Lett. B764 (2017) 289-294, arXiv:1609.01253.
  • A. Ijjas, P.J. Steinhardt. Classically stable non-singular cosmological bounces, Phys.Rev.Lett. 117 (2016) 121304, arXiv:1606.08880.
  • A. Ijjas, J. Ripley, P.J. Steinhardt. NEC violation in mimetic cosmology revisited, Phys.Lett.B 760 (2016) 132-138, arXiv:1604.08586.
  • A. Ijjas, P.J. Steinhardt. Implications of Planck2015 for inflationary, ekpyrotic and anamorphic bouncing cosmologies, Class.Quant.Grav. 33 (2016) 044001, arXiv:1512.09010.
  • A. Ijjas, P.J. Steinhardt. The anamorphic universe, JCAP 10 (2015) 001, arXiv:1507.03875.
  • A. Levy, A. Ijjas, P.J. Steinhardt. Scale-invariant perturbations in ekpyrotic cosmologies without fine-tuning of initial conditions, Phys.Rev.D. 92 (2015) 063524, arXiv:1506.01011.
  • A. Ijjas, J.-L. Lehners, P.J. Steinhardt. A general mechanism for producing scale-invariant perturbations and small non-Gaussianity in ekpyrotic models, Phys.Rev.D. 89 (2014) 123520, arXiv:1404.1265.
  • A. Ijjas, P.J. Steinhardt, A. Loeb. Inflationary schism, Phys.Lett.B 736 (2014) 142–146, arXiv:1402.6980.
  • A. Ijjas, P.J. Steinhardt, A. Loeb. Scale-free primordial cosmology, Phys.Rev.D 89 (2014) 023525, arXiv:1309.4480.
  • A. Ijjas, P.J. Steinhardt, A. Loeb. Inflationary paradigm in trouble after Planck2013, Phys.Lett.B 723 (2013) 261–266, arXiv:1304.2785. [Featured in New Scientist 2937 (2013) 38–41 and Quanta Magazine January 30, 2015.]
Books:
  • A. Ijjas, P.J. Steinhardt. Rethinking Cosmology, under contract with Princeton University Press.
  • A. Ijjas. Der Alte mit dem Würfel. Ein Beitrag zur Metaphysik der Quantenmechanik, Göttingen: Vandenhoeck & Ruprecht 2011, pp.223. [In German, English title: The old one with the dice: a contribution to the metaphysics of quantum mechanics.]
Other publications:
  • A. Ijjas. What if there was no big bang?, New Scientist, 08/17 (2019), pp 42-45. | invited feature article |
  • A. Ijjas, P.J. Steinhardt, A. Loeb. Pop goes the universe Scientific American, 02/2017, pp 32-39. | | FAQs
  • A. Ijjas, P.J. Steinhardt. Do we live in an anamorphic universe? PBS NOVA: The Nature of Reality 01/2016 |

talkstalkss

selected recent colloquia, seminars,etc.
    2023-24:
  • NY Academy of Sciences, New York, NY, Jun 2024.
  • IDA, Alexandria, VA, Dec 2023.
  • MITLL, Lexington, MA, Dec 2023.
  • LLNL, Livermore, CA, Oct 2023.
  • World Science Festival, New York, NY, Sept 2023. Video
    • 2022-23:
  • Royal Society Scientific Meeting: Probing the quantum origin of spacetime, UK, Jan 2023.
  • Gravity Group Seminar, Ole Miss, Oxford, MS, Oct 2022.
  • Ultralocality and the solution to the Homogeneity, Isotropy and Flatness problems. Informal Cosmology Seminar, Princeton, NJ, Oct 2022. Video
  • YITP Seminar, Stony Brook, NY, Sept 2022.
  • Clay Mathematics Insititute Workshop: Stability and Instability in General Relativity, Oxford, UK, Sept 2022.
    • 2021-22:
  • New frontiers in early-universe cosmology, Lorentz Center workshop: A Shot in the Dark - New Challenges in Cosmology, Leiden, NL, June 2022.
  • Advancing Fundamental Cosmology with Numerical Relativity, NBIA, Copenhagen, DK, May 2022.
  • Ultralocality, slow contraction, and beyond, HEP Seminar, CCPP-NYU, New York, NY, Apr 2022.
  • Entropy, Black Holes, and the Early Universe, Seminar: Institute for Theoretical Physics, KU Leuven, Belgium, Mar 2022.
  • Ultralocality and the robustness of slow contraction to cosmic initial conditions, Strong Gravity Seminar, Perimeter Institute, Waterloo, ON, Feb 2022.
  • Numerical Relativity and Cosmology, Fundamental Theory Seminar, Penn State, State College, PA, Feb 2022.
  • Numerical Relativity and Cosmology, Brown Bag, CCPP-NYU, New York, NY, Jan 2022. Video
  • New Frontiers in Early-Universe Cosmology, Brookhaven Forum, Upton, NY, Nov 2021.
  • Entropy, Black Holes, and the Early Universe, ITC Colloquium, Harvard University, Cambridge, MA, Oct 2021.
  • Smoothing, entropy, and the new cyclic universe, Theory Group Seminar, The University of Texas at Austin, Oct 2021.
  • New Frontiers in Fundamental Cosmology, Astronomy Colloquium, Ohio State University, Columbus, OH, Sept 2021.
    • 2020-21:
  • Open Vistas for Early-Universe Cosmology, Cosmo '21, University of Illinois Urbana-Champaign, August 2021.
  • Ultralocality and the robustness of slow contraction to cosmic initial conditions, Theoretical Physics Seminar, Goethe University, Frankfurt, Germany, July 2021.
  • A New Kind of Cyclic Universe, Lichtenberg Seminar Series, Bonn University, Bonn, Germany, May 2021.
  • Ultralocality and the robustness of slow contraction to cosmic initial conditions, Princeton Gravity Initiative Seminar Series, Princeton, NJ, May 2021.
  • The Robustness of Slow Contraction to Cosmic Initial Conditions, C3-Seminar, KU Leuven, Belgium, Nov 2020.
  • Open Issues in Early-Universe Cosmology, Physics Colloquium, Oakland University, Rochester, MI, Nov 2020.
  • Big Bang or Big Bounce: What happened 13.8 billion years ago?, Physics Colloquium, Technion, Haifa, Israel, Nov 2020.
  • The Robustness of Slow Contraction to Cosmic Initial Conditions, Fundamental Physics Seminar, The Pennsylvania State University, University Park, PA, Oct 2020.
  • The Robustness of Slow Contraction to Cosmic Initial Conditions, ACR Seminar, Albert Einstein Institute, Potsdam-Golm, Oct 2020.
  • Cosmology Reconsidered, Colloquium, Institute for Theoretical Physics, Leibniz University Hannover, Oct 2020.
  • The Robustness of Slow Contraction to Cosmic Initial Conditions, Keynote, UK Cosmology Day, Sheffield University, UK, Sept 2020.
    • 2019-20:
  • New Kind of Cosmology: No Bang - No Crunch - No Beginning - No End, Simons Workshop on the Occasion of Reopening the Flatiron Institute, NYC, USA, July 2020.
  • Cosmology in in the era of gravitational wave astronomy, Colloquium, Bielefeld, Germany, May 2020.
  • Numerical Relativity and Cosmology: An interesting Case Study, BHI Colloquium, Harvard University, Cambridge, MA, Feb 2020.
  • Simple Universe - Complex Initial Conditions?, Physics Seminar, Harvard University, Cambridge, MA, Feb 2020.
  • The virtues of slow contraction and other perks of bouncing, RTG Colloquium, ZARM Bremen, Germany, Feb 2020.
  • No beginning for space-time, and other perks of bouncing, ASC Theory Seminar, Ludwig-Maximilians-Universität, Munich, Germany, Dec 2019.
  • And now for something completely different!, International Conference Cosmic Controversies, Chicago, IL, Oct 2019.
  • The virtues of slow contraction, and other perks of bouncing, Origins of the Universe Annual Meeting, Simons Foundation, New York, NY, Sept 2019. Video
    • 2018-19:
  • (Re-)Connecting Cosmology with General Relativity, International Conference Current Themes in Gravitational Physics, Copenhagen, DK, Aug 2019.
  • Explaining the early universe: a comparative review of competing paradigms, International Conference CosmoGold, IAP Paris, France, Jun 2019.
  • Cosmology with a Bounce, International Symposium Understanding Our Place in the Cosmos, Jerusalem, Israel, Mar 2019.
  • Big Bang vs Big Bounce, Physics Colloquium, Brown University, Providence, RI, Feb 2019.
  • Big Bang vs Big Bounce, Physics Colloquium, Syracuse University, Syracuse, NY, Feb 2019.
  • (Re)Connecting Cosmology and General Relativity, High-Energy Physics Seminar, California Institute of Technology, Pasadena, CA, Jan 2019.
  • Stability and the Gauge Problem in Early-Universe Cosmology, TEP Seminar, Bhaumik Institute for Theoretical Physics, UCLA, Los Angeles, CA, Oct 2018.
  • Bouncing Cosmology: Basics and Recent Progress, AEI Colloquium, Max-Planck-Institute for Gravitational Physics, Hannover, Germany, Oct 2018.
  • Advances in constructing smooth cosmological bounces, Origins of the Universe Annual Conference, Simons Foundation, New York, NY, Sept 2018.
    • 2017-18:
  • New frontiers in early-universe cosmology and numerical general relativity, Lise Meitner Symposium of the Max Planck Society, Harnack Haus, Berlin, Germany, Jul 2018.
  • Introduction to recent advances and open issues in bouncing cosmologies, Simons Workshop Frontiers in Cosmology and Numerical Relativity, Salzburg, Austria, Jul 2018.
  • Space-time slicing in Horndeski theories and its implications for non-singular bouncing solutions, High-Energy Theory/Cosmology Seminar, Johns Hopkins University, Baltimore, MD, Apr 2018.
  • Expected CMB polarization signals in Bouncing Cosmologies, KISS workshop Designing Future CMB Experiments, California Institute of Technology, Pasadena, CA, Mar 2018.
  • Bouncing Cosmology made simple, Statistical Cosmology Seminar, Flatiron Institute, New York, NY, Mar 2018.
  • Cosmology without a Big Bang, Physics Colloquium, University of Chicago, Chicago, IL, Feb 2018.
  • Towards a non-singular bouncing cosmology, BHI Colloquium, Harvard University, Cambridge, MA, Oct 2017.

contactcontact

how to reach me

E-mail is the best way to get in touch with me.

email

ai2328@nyu.edu

address
The Center for Cosmology and Particle Physics
Department of Physics
New York University
726 Broadway
New York, NY, 10003
USA
office

915