Complete positivity bounds for the 22 aQGC coefficients in SMEFT restrict the viable parameter space to approximately 0.0313% of the naive total.
Dispersion Relation Bounds for pi pi Scattering
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abstract
Axiomatic principles such as analyticity, unitarity and crossing symmetry constrain the second derivative of the pi pi scattering amplitudes in some channels to be positive in a region of the Mandelstam plane. Since this region lies in the domain of validity of chiral perturbation theory, we can use these positivity conditions to bound linear combinations of \bar{l}_1 and \bar{l}_2. We compare our predictions with those derived previously in the literature using similar methods. We compute the one-loop pi pi scattering amplitude in the linear sigma model (LSM) using the MS-bar scheme, a result hitherto absent in the literature. The LSM values for \bar{l}_1 and \bar{l}_2 violate the bounds for small values of m_sigma/m_pi. We show how this can occur, while still being consistent with the axiomatic principles.
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Defines IR-finite amplitudes M_E that preserve analyticity and unitarity to derive positivity bounds on EFTs including electromagnetism and gravity in D=4.
Multipositivity bounds derived from planar tree-level scattering amplitudes constrain Wilson coefficients of the chiral Lagrangian from below by the chiral anomaly.
citing papers explorer
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Full positivity bounds for anomalous quartic gauge couplings in SMEFT
Complete positivity bounds for the 22 aQGC coefficients in SMEFT restrict the viable parameter space to approximately 0.0313% of the naive total.
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Positivity with Long-Range Interactions
Defines IR-finite amplitudes M_E that preserve analyticity and unitarity to derive positivity bounds on EFTs including electromagnetism and gravity in D=4.
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Multipositivity Constrains the Chiral Lagrangian
Multipositivity bounds derived from planar tree-level scattering amplitudes constrain Wilson coefficients of the chiral Lagrangian from below by the chiral anomaly.
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