# Freddy Cachazo

Gluskin Sheff Freeman Dyson Chair in Theoretical Physics at Perimeter Institute

Areas of Research:
Phone: x8501

## Research Interests

In recent years it has become clear that the scattering matrix of massless particles is a very special object. Massless particles are the backbone of our best theory of nature; the Standard Model of particle physics and gravity. In 2003, Witten succeeded in combining twistor theory and string theory to produce a new formulation for the scattering matrix of gauge bosons - massless particles of helicity plus or minus one. Since then finding a similar formulation for gravitons - particles with helicity plus or minus two - has been a very important open problem. In 2012, in collaboration with Y. Geyer (a PSI student), I found one such formulation. Not long after this first formulation was found, I found a second one with D. Skinner (a PI postdoctoral fellow). All these constructions are based on four dimensional kinematics. A natural question is whether similar constructions can be found in any dimension. Such a general formulation could lead to a deeper understanding of field theory in general. In 2013 and in collaboration with E. Yuan (a PI graduate student) and S. He (a PI postdoctoral fellow), I found such a construction. This is now known as the CHY construction and it gives tree-level scattering matrices of a variety of theories, including gluons and gravitons, in any dimensions as integrals over the space of n-punctured spheres. This new formulation has become an active area of research. In 2014 our group found CHY representations for theories such as Dirac-Born-Infeld and Galileons. Very recently we have found extensions of the theory of pions using soft limits which were previously hidden and become manifest using their CHY formulation.

## Positions Held

• September 2009 - June 2010 School of Natural Sciences. Institute for Advanced Study. Princeton NJ. Member.
• 2005-present. Perimeter Institute. Faculty Member
• 2002-2005 School of Natural Sciences. Institute for Advanced Study. Princeton NJ. Postdoctoral Member.

## Awards

• 2016 CAP-CRM Prize in Theoretical and Mathematical Physics.
• 2014 New Horizons Prize (FPP).
• 2012 Herzberg Medal (CAP).
• 2011 Rutherford Medal, Royal Society of Canada (RSC).
• 2009 Gribov Medal, European Physical Society (EPS)
• Early Reseach Award of Ontario (ERA).

## Recent Publications

• F. Cachazo, P. Cha and S. Mizera, Extensions of Theories from Soft Limits, JHEP 1606, 170 (2016) [arXiv: 1604.03893 [hep-th]].
• F. Cachazo, S. He and E. Y. Yuan, One-Loop Corrections from Higher Dimensional Tree Amplitudes, JHEP 1608, 008 (2016) [arXiv: 1512.05001 [hep-th]].
• N. Arkani-Hamed, J. L. Bourjaily, F. Cachazo, A. Postnikov and J. Trnka, On-Shell Structures of MHV Amplitudes Beyond the Planar Limit, JHEP 1506, 179 (2015) [arXiv: 1412.8475 [hep-th]].
• F. Cachazo, S. He and E. Y. Yuan, Scattering Equations and Matrices: From Einstein To Yang-Mills, DBI and NLSM, JHEP 1507, 149 (2015) [arXiv: 1412.3479 [hep-th]].
• N. Arkani-Hamed, J. L. Bourjaily, F. Cachazo and J. Trnka, Singularity Structure of Maximally Supersymmetric Scattering Amplitudes, Phys. Rev. Lett. 113, no. 26, 261603 (2014) [arXiv: 1410.0354 [hep-th]].
• F. Cachazo, S. He and E. Y. Yuan, Einstein-Yang-Mills Scattering Amplitudes From Scattering Equations, JHEP 1501 (2015) 121 [arXiv: 1409.8256 [hep-th]].
• F. Cachazo, S. He and E. Y. Yuan, Scattering of Massless Particles: Scalars, Gluons and Gravitons, JHEP 1407, 033 (2014) [arXiv: 1309.0885 [hep-th]].
• F. Cachazo, S. He and E. Y. Yuan, Scattering of Massless Particles in Arbitrary Dimensions, Phys. Rev. Lett. 113, no. 17, 171601 (2014) [arXiv: 1307.2199 [hep-th]].
• F. Cachazo, S. He and E. Y. Yuan, Scattering equations and Kawai-Lewellen-Tye orthogonality, Phys. Rev. D 90, no. 6, 065001 (2014) [arXiv: 1306.6575 [hep-th]].
• F. Cachazo, S. He and E. Y. Yuan, Scattering in Three Dimensions from Rational Maps, JHEP 1310, 141 (2013) [arXiv: 1306.2962 [hep-th]].
• F. Cachazo and D. Skinner, Gravity from Rational Curves, Phys. Rev. Lett. 110, 161301 (2013) [arXiv: 1207.0741 [hep-th]].
• F. Cachazo, L. Mason and D. Skinner, Gravity in Twistor Space and its Grassmannian Formulation, SIGMA 10, 051 (2014) [arXiv: 1207.4712 [hep-th]].
• F. Cachazo and G. Zhang, Minimal Basis in Four Dimensions and Scalar Blocks, arXiv: 1601.06305 [hep-th].
• F. Cachazo and H. Gomez, Computation of Contour Integrals on {\cal M}_{0,n}, arXiv: 1505.03571 [hep-th].
• F. Cachazo, S. He and E. Y. Yuan, New Double Soft Emission Theorems, arXiv: 1503.04816 [hep-th].
• F. Cachazo and E. Y. Yuan, Are Soft Theorems Renormalized?, arXiv: 1405.3413 [hep-th].
• F. Cachazo and A. Strominger, Evidence for a New Soft Graviton Theorem, arXiv: 1404.4091 [hep-th].
• F. Cachazo, S. He and E. Y. Yuan, Scattering of Massless Particles in Arbitrary Dimension, arXiv: 1307.2199 [hep-th].
• F. Cachazo, S. He and E. Y. Yuan, Scattering in Three Dimensions from Rational Maps, arXiv: 1306.2962 [hep-th].
• F. Cachazo, S. He and E. Y. Yuan, Scattering Equations and KLT Orthogonality, arXiv: 1306.6575 [hep-th].
• F. Cachazo, Resultants and Gravity Amplitudes, arXiv: 1301.3970 [hep-th].
• Grassmannian Geometry of Scattering Amplitudes, N. Arkani-Hamed, J. Bourjaily, F. Cachazo, A. Goncharov, A. Postnikov, J. Trnka, Cambridge University Press, 2016

## Seminars

• Plenary talk on S-Matrix Theory", Canadian Association of Physicist Congress, University of Ottawa, Canada, June 2016.
• Plenary talk on Unification and Extension", Theory CANADA 11, Carleton University, Ottawa, Canada, June 2016.
• Plenary talk on "Developments in String and Field Theory" at the European Physical Society 2015 meeting in Vienna, Austria, July 2015.
• Plenary talk at PASCOS 2015, Abdus Salam ICTP, Trieste, Italy, June 2015
• Plenary talk at Amplitudes 2015, EHT, Zurich, Switzerland, June 2015
• Five lectures at TASI 2015 "New Frontiers in Fields and Strings", University of Colorado, Colorado, USA, June 2015
• Colloquium. Department of Physics, University of Toronto, Toronto, Canada, March 2015
• Series of three lectures given at the Spring School on Superstring Theory and Related Topics. Abdus Salam ICTP, Trieste, Italy, March 2015
• Plenary talk at STRINGS 2014 in Princeton USA.
• Plenary talk at Quantum Gravity in Paris 2014. Paris. March 2014.
• Academics Program Department Presentation to the Scientific Advisory Committee, October 2015.
• PIRSA:15060045, Welcome to Convergence - Opening Panel: Physics Today, 2015-06-22, Convergence
• PIRSA:15050055, Scattering Amplitudes and Riemann Surfaces, 2015-05-27, Geometry and Physics 2015
• PIRSA:15050063, Scattering Amplitudes and Riemann Surfaces, 2015-05-26, Geometry and Physics 2015
• PIRSA:15050047, Scattering Amplitudes and Riemann Surfaces, 2015-05-25, Geometry and Physics 2015
• PIRSA:14100026, 14/15 PSI - Conformal Field Theory - Lecture 14, 2014-10-24, 14/15 PSI - Conformal Field Theory
• PIRSA:14100025, 14/15 PSI - Conformal Field Theory - Lecture 13 , 2014-10-23, 14/15 PSI - Conformal Field Theory
• PIRSA:14100024, 14/15 PSI - Conformal Field Theory - Lecture 12 , 2014-10-22, 14/15 PSI - Conformal Field Theory
• PIRSA:14100023, 14/15 PSI - Conformal Field Theory - Lecture 11 , 2014-10-21, 14/15 PSI - Conformal Field Theory
• PIRSA:14100022, 14/15 PSI - Conformal Field Theory - Lecture 10, 2014-10-20, 14/15 PSI - Conformal Field Theory
• Quantum Gravity Group Meeting. Resultants and Gravity Amplitudes.