Freddy Alexander Cachazo is a Venezuelan -born theoretical physicist who holds the Gluskin Sheff Freeman Dyson Chair in Theoretical Physics at the Perimeter Institute for Theoretical Physics in Waterloo , Ontario , Canada .
16-408: MHV may refer to: MHV Amplitudes (particle physics) - maximally helicity violating amplitudes MHV connector (electronics) - miniature high voltage RF connector Mojave Air & Space Port , FAA and IATA code Mouse hepatitis virus Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with
32-823: A particular helicity and the other two have the opposite helicity. These amplitudes are called MHV amplitudes, because at tree level, they violate helicity conservation to the maximum extent possible. The tree amplitudes in which all gauge bosons have the same helicity or all but one have the same helicity vanish. MHV amplitudes may be calculated very efficiently by means of the Parke–Taylor formula. Although developed for pure gluon scattering, extensions exist for massive particles, scalars (the Higgs ) and for fermions ( quarks and their interactions in QCD ). Work done in 1980s by Stephen Parke and Tomasz Taylor found that when considering
48-456: A technique of "sewing" MHV amplitudes together (with some off-shell continuation) to build arbitrarily complex tree diagrams. The rules for this formalism are called the CSW rules (after Freddy Cachazo , Peter Svrcek , Edward Witten ). The CSW rules can be generalised to the quantum level by forming loop diagrams out of MHV vertices. There are missing pieces in this framework, most importantly
64-409: Is now made of these techniques. Freddy Cachazo He is known for the contributions to quantum field theory through the study of scattering amplitudes , in particular in quantum chromodynamics , N = 4 supersymmetric Yang–Mills theory and quantum gravity . His contributions include BCFW recursion relations , the CSW vertex expansion and the amplituhedron . In 2014, Cachazo was awarded
80-502: Is the reliance on cut-constructibility to compute the loop integrals. This therefore cannot recover the rational parts of amplitudes (i.e. those not containing cuts). A Lagrangian whose perturbation theory gives rise to the CSW rules can be obtained by performing a canonical change of variables on the light-cone Yang–Mills (LCYM) Lagrangian. The LCYM Lagrangrian has the following helicity structure: The transformation involves absorbing
96-441: The ( + + − ) {\displaystyle (++-)} vertex, which is clearly non-MHV in form. In pure Yang–Mills theory this vertex vanishes on-shell , but it is necessary to construct the ( + + + + ) {\displaystyle (++++)} amplitude at one loop. This amplitude vanishes in any supersymmetric theory, but does not in the non-supersymmetric case. The other drawback
112-717: The New Horizons Prize for uncovering numerous structures underlying scattering amplitudes in gauge theories and gravity . After graduating from Simón Bolívar University in 1996, Cachazo attended a year-long Postgraduate Diploma Programme at the International Centre for Theoretical Physics (ICTP) in Trieste , Italy . He was admitted in Harvard University , where he completed the Ph.D. under
128-543: The recursion relations for the computation of scattering amplitudes , which opened a new window for computations required at particle accelerators, such as the Large Hadron Collider . With Nima Arkani-Hamed and collaborators, he studied N = 4 supersymmetric Yang–Mills theory and showed how to compute amplitudes at any order in the perturbation theory . He co-discovered a new formalism unifying gauge theory and gravity in any space-time dimension, known as
144-612: The CSW approach turn out to be recovered within the MHV Lagrangian framework via evasions of the S-matrix equivalence theorem. An alternative approach to the MHV Lagrangian recovers the missing pieces mentioned above by using Lorentz-violating counterterms. BCFW recursion, also known as the Britto–Cachazo–Feng–Witten (BCFW) on-shell recursion method, is a way of calculating scattering amplitudes. Extensive use
160-818: The Cachazo-He-Yuan formulation. In 2009, he was awarded the Gribov Medal for an outstanding work by a young physicist from the European Physical Society . Two year later he won the Rutherford Medal , an equivalent prize awarded by the Royal Society of Canada . In 2012, Canadian Association of Physicists awarded Cachazo with the Herzberg Medal . Finally, he won the 2014 New Horizons Prize , which by many
176-405: The non-MHV three-point vertex into the kinetic term in a new field variable: When this transformation is solved as a series expansion in the new field variable, it gives rise to an effective Lagrangian with an infinite series of MHV terms: The perturbation theory of this Lagrangian has been shown (up to the five-point vertex) to recover the CSW rules. Moreover, the missing amplitudes which plague
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#1732780577895192-534: The number of gluons present: The compactness of these amplitudes makes them extremely attractive, particularly for data taking at the LHC , for which it is necessary to remove the dominant background of standard model events. A rigorous derivation of the Parke–Taylor amplitudes was given by Berends and Giele. The MHV were given a geometrical interpretation using Witten's twistor string theory which in turn inspired
208-407: The scattering of many gluons, certain classes of amplitude vanish at tree level; in particular when fewer than two gluons have negative helicity (and all the rest have positive helicity): The first non-vanishing case occurs when two gluons have negative helicity. Such amplitudes are known as "maximally helicity violating" and have an extremely simple form in terms of momentum bilinears, independent of
224-906: The supervision of Cumrun Vafa in 2002. Cachazo was a post-doctoral member of the Institute for Advanced Study (IAS) in Princeton , New Jersey in 2002-05 and 2009-10. In 2005, he became a faculty member at the Perimeter Institute for Theoretical Physics in Waterloo , Ontario , Canada , as well as an Adjoint Faculty at the nearby University of Waterloo . He currently holds the Gluskin Sheff Freeman Dyson Chair in Theoretical Physics. Cachazo's research concerns quantum field theory ,
240-711: The title MHV . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=MHV&oldid=699062731 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages MHV Amplitudes In theoretical particle physics , maximally helicity violating amplitudes (MHV) are amplitudes with n {\displaystyle n} massless external gauge bosons, where n − 2 {\displaystyle n-2} gauge bosons have
256-466: The underlying theory describing fundamental interactions of particles and space-time itself. The research program is to understand their deep structure through the study of scattering amplitudes . Such understanding allows for both efficient computation of the probabilities of physical processes occurring and insights into the unknown structures of the gauge theories and gravity . Together with Ruth Britto , Bo Feng and Edward Witten , he introduced
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