Scattering Amplitudes and the Positive Grassmannian
3
Scattering of elementary particles
4
Theorist's perspective What happens during scattering experiment?
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New picture: on-shell diagrams Remarkable connection to mathematics
6
Motivation
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Elementary particles and forces
8
Quantum field theory
9
Scattering amplitude
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Perturbative expansion
11
Feynman diagrams
12
Search for new physics
13
Amplitudes of gluon's
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Parke-Taylor formula
15
Amplitudes as a new field
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Problem with Feynman diagrams
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New objects
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Kinematics of massless particles
19
Fundamental amplitudes
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Definition of on-shell diagrams
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On-shell diagrams
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Amplitudes from on-shell diagrams
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Simple examples
24
Simplicity revealed
25
Identity moves
26
Precise statement
27
Permutations
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New look at permutations
29
Identity moves
30
Yang-Baxter moves
31
Reduced information
32
Positive Grassmannian
33
Positive matrices
34
Face variables
35
Perfect orientation
36
Boundary measurement
37
Entries of matrix
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Positive matrix
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Edge variables
40
Cell in the Positive Grassmannian
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Example of configuration
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Example of stratification
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Relation to permutations
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Boundary operator
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Stratification of the positive Grassmannian
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Summary of positive Grassmannian
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Connection to cluster algebras
48
Seed and mutation
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Square-move
50
Surprising connection
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Connection
52
Cluster transformation
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Momentum conservation
54
Geometry of delta function
55
Logarithmic form
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Derivation: starting with 3pt
57
Amalgamation procedure
58
New procedure
59
Conclusion
60
Summary
61
Amplituhedron
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Non-planar on-shell diagrams
63
Resources
64
Thank you!
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Amplituhedron
Description:
Explore the fascinating world of scattering amplitudes and their connection to the positive Grassmannian in this comprehensive lecture. Delve into the theoretical foundations of particle physics, starting with elementary particles and forces, and progressing through quantum field theory and scattering amplitudes. Discover the limitations of traditional Feynman diagrams and learn about innovative approaches like on-shell diagrams. Examine the mathematical underpinnings, including permutations, positive matrices, and the stratification of the positive Grassmannian. Investigate the surprising connections to cluster algebras and explore advanced concepts such as the Amplituhedron. Gain insights into cutting-edge research in theoretical physics and mathematics, with discussions on non-planar on-shell diagrams and resources for further study.
Scattering Amplitudes and Positive Grassmannian by Jaroslav Trnka