A physicist’s research

To see open hosted preprints and journal articles follow the inSPIRE link in the sidebar, or click here.

My group’s web page is hosted at http://fancyphysics.org, where you can find my recent grant proposals here.

Big Questions:

• What unifies our physical predictions?
• How does the relatively calm macroscopic universe survive and emerge from the violent quantum fluctuations of its underlying microphysics?
• How do classical notions of space and time emerge from fundamental principles, and what governs their evolution?
• How are should our classical understanding of space and time be modified to build intuition of underlying quantum reality?
• How might our current understanding of quantum mechanics need to evolve to resolve answers to the above questions?

Broad projects:

• Double copy unification of relativistic quantum field theories.
• Double copy relevance for classical predictions in perturbative gravity.
• Predictivity question re: pointlike quantum field theories of gravity. (Are all QFT of gravity effective out of necessity?)
• Relevance of field-theory double-copy to ultra-soft properties of string theory. (See Z-theory.)
• Effective field theory of large scale structure (EFTofLSS)
• \(\alpha\)-Attractor Inflationary models.

Research highlights:

• Discovered the color-kinematic duality in gauge theories and the associated double-copy structure of tree and multi-loop gravity theory amplitudes. Importance: Striking clarification of the intimacy between gauge and gravity theories, redundancy present in both, changing the way we calculate in and think about these theories. (For a textbook introduction can now see Anthony Zee’s Quantum Field Theory in a Nutshell, 2nd Ed., Chapter N.4. For popular science account see May 2012 cover story of Scientific American.)
  _{with: Bern, Johansson.}
• Discovered the \((n-3)!\) basis (“BCJ” basis) of gauge-theory tree-level amplitudes. Importance: Led to proofs of explicit tree-level gauge-gravity amplitude-level relations (KLT) in field theory, subsequent discovery of analogous structure in string theory led to closed form string-KLT expressions and all-order expressions for string tree-amplitudes.
  _{with: Bern, Johansson.}
• Established, through explicit calculation, that the high energy behavior of \({\cal N}=8\) maximal supergravity, contrary to popular opinion, is much better than expected – matching the known finite maximal gauge theory – through 4 loops as of now. Importance: If finite to all orders it is because of an unrecognized symmetry or mechanism whose apprehension will teach something very new about gravity.
  _{with: Bern, Dixon, Kososwer, Roiban, Johansson.}
• Established the predictive impact of certain anomalies relevant to \({\cal N}\le4\) supergravity theories, and perhaps more strikingly their underlying double-copy origins. Importance: There is mounting evidence to suggest that failure of predictivity for pure supergravity theories in four-dimensions are directly related to these anomalies, which * do not exist for \({\cal N}>5\) supergravity theories.*
  _{with: Kallosh, Roiban, Tseytlin.}
• Established the effective field theory of cosmological large-scale structure. Importance: opens up a rigorous new way to analytically study large-scale structure taking into account the nonlinearity of small-scale perturbations with telling agreement between numerical simulations and analytic theory.
  _{with: Foreman, Green, Hertzberg, Senatore.}
• Discovered a systematic, theory-independent, approach to unitarity-based multi-loop perturbative quantization - Method of Maximal Cuts. Importance: Establishes hierarchy of relevance of \(S\)-matrix information for a given theory. Trivialized unitarity state-sums for theories whose spectra are truncations of \({\cal N}=4\) super Yang-Mills¹ in 4D to just tracking glue around MHV-vertex graphs.
  _{with: Bern, Dixon, Kosower, Roiban, Johansson.}
• Established covariant prescriptions for deforming non-linear duality-invariant theories. Importance: demonstration of freedom to introduce counterterms to theories protected by duality-invariance, may be relevant to UV questions in gravity.
  _{with: Broedel, Ferrara, Kallosh, Roiban}
• Established Z-theory as the effective bi-colored scalar theory which encodes all the \(\alpha'\) corrections of the open-string, and thus encodes all the ultra-soft UV behavior. Importance: Scalars theories are technically much simpler to analyze. Z-theory amplitudes offer a fascinating laboratory to study the emergence of stringy-behavior in a new and technically much simpler context.
  _{with: Mafra and Schlotterer}