Questions tagged [amplituhedron]
A geometric object whose volume is conjectured to be related to scattering amplitudes. It is used mostly in string theory.
31 questions
1 vote
0 answers
93 views
EFTs in the EFT-hedron and strongly coupled UV-completions?
The EFT-hedron developed by Arkani-Hamed and collaborators encode EFTs that can be UV-complete (https://arxiv.org/abs/2012.15849). But does it only encode EFTs that can be completed by weakly coupled ...
- 3,374
4 votes
0 answers
108 views
Negative geometries and positivity bounds?
Recently, Nima Arkani-Hamed and collaborators have discovered the relation between positive geometries that encode basic features of QFTs called positivity constraints like unitarity, causality, ...
- 3,374
2 votes
0 answers
77 views
3-Particle Kinematics and Parity of Operators
Recall that if the momentum of scattering amplitudes is taken to be complex and from little group scaling that the 3-particle interaction for massless particles of any spin is given as \begin{equation}...
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1 vote
1 answer
131 views
"Fourier Transformation" of angle spinors to twistor variables
This relates to the derivation of equation (5.15) if Elvang and Huang's textbook. The idea is to transform the spinor helicity variables we are using, $(|i\rangle_{\dot{a}},[j|^a)$ to go into twistor ...
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1 vote
0 answers
95 views
Scalar QED amplitudes with BCFW Recursion Relation
(This question comes from exercise 3.5 of Elvang's and Huang's "Scattering amplitudes in Gauge Theory and Gravity" book. This is not for a class, this is to learn a new technique; albeit I ...
- 1,212
2 votes
1 answer
166 views
Complex BCFW-shift of Parke-Taylor amplitude
(This question stems from problem 3.3 of Elvang's and Huang's "Scattering Amplitudes in Gauge Theory and Gravity" book). Consider the Parke-Taylor amplitude given as \begin{equation} A_n[1^- ...
- 1,212
5 votes
0 answers
387 views
Every possible QFT from positive geometry?
Physicist Nima Arkani-Hamed has taken an interesting approach to understand fundamental physics based on geometry (specifically, positive geometry constructions). This started with his work with ...
- 3,374
0 votes
2 answers
260 views
Why does the amplitude not increase the speed of the sound wave?
The way I see it,if there's a set up A which has 5 particles and another set up B which also has 5 particles,and assuming everything else is same in these set up,like distance between particles etc,if ...
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2 votes
1 answer
142 views
Positive geometry and log singularities
In order to define a positive geometry it is a requirement that has to be a logarithmic singularities on the boundaries, for example for an interval (endpoints $a$ and $b$) the canonical form is $$\...
- 183
1 vote
1 answer
189 views
Kinematics of Scattering Amplitudes in $\left(2, 2\right)$ Signature within the Amplituhedron
I am just working my way through the concepts of Amplituhedron and often stumble across the phrase [...] in $\left(2,2\right)$ signature $\lambda$, $\tilde{\lambda}$ are real and independent [...] ...
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1 vote
0 answers
140 views
Differential forms in projective space
I am currently reading some paper about the Amplituhedron, and it is using projective geometric way to present amplitudes. How can we define forms in projective space to measure volume for a polytope?
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1 vote
0 answers
49 views
Question about an NHMV amplitude (in the book by Elvang et al) and its representation by plabic graphs
I am looking at the NMHV amplitude with six particles with three positive helicities (particles 1,3,5). This amplitude is given in Eq.(10.1), which is [3,1,6,5,4]+[3,2,1,6,5]+[3,2,1,5,4] My question ...
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0 votes
1 answer
136 views
Questions about the plabic graphs in the amplituhedron program
I am reading the book by Arkani-Hamed et al. I see how one can get the permutation from a plabic graph, and I see how different plabic graphs can be shown to be equivalent through moves. But I don't ...
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1 vote
0 answers
83 views
Ordering ambiguity in the spinor helicity formalism of scattering amplitudes
I am following Nima's course on "Quantum mechanics and spacetime, total positivity and motives", and I wonder if there's a direct way to understand the ordering ambiguity when we are summing ...
1 vote
1 answer
649 views
Veneziano amplitude in quantum field theory
It is well-known, that Veneziano amplitude is the string scattering amplitude for the scattering of four open bosonic strings in their tachyon states. Are some QFT models, in which amplitude is ...
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