scholarly journals Pionic hydrogen and deuterium

2021 ◽  
Author(s):  
Detlev Gotta ◽  
L. M. Simons
Keyword(s):  
High Resolution ◽  
Effective Field Theories ◽  
Strong Interaction ◽  
Pion Production ◽  
Effective Field ◽  
Low Energy ◽  
Field Theories ◽  
Pionic Hydrogen ◽  
Pion Nucleon ◽  
Scattering Lengths

The measurement of strong-interaction shift and broadening in pionic hydrogen and deuterium yields pion-nucleon scattering lengths as well as the threshold pion-production strength on isoscalar NN pairs. Results from recent high-resolution experiments at PSI using crystal spectrometers allow important comparisons with the outcome of the modern low-energy description of QCD within the framework of effective field theories.

scholarly journals The Swampland Conjectures: A Bridge from Quantum Gravity to Particle Physics

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 273
Author(s):  
Mariana Graña ◽  
Alvaro Herráez
Keyword(s):  
Effective Field Theories ◽  
Quantum Gravity ◽  
Particle Physics ◽  
Effective Field ◽  
Low Energy ◽  
Field Theories ◽  
Neutrino Masses ◽  
Higgs Potential ◽  
Photon Mass ◽  
Effective Theories

The swampland is the set of seemingly consistent low-energy effective field theories that cannot be consistently coupled to quantum gravity. In this review we cover some of the conjectural properties that effective theories should possess in order not to fall in the swampland, and we give an overview of their main applications to particle physics. The latter include predictions on neutrino masses, bounds on the cosmological constant, the electroweak and QCD scales, the photon mass, the Higgs potential and some insights about supersymmetry.

scholarly journals Interface junctions in QCD${}_4$

2021 ◽  
Vol 10 (4) ◽  
Author(s):  
Pranay Gorantla ◽  
Ho Tat Lam
Keyword(s):  
Effective Field Theories ◽  
Quantum Chromodynamics ◽  
Effective Field ◽  
Low Energy ◽  
Coupling Constants ◽  
Field Theories ◽  
Scalar Theory ◽  
Complex Mass ◽  
Spatially Varying ◽  
Chern Simons

We study 3+1 dimensional SU(N)SU(N) Quantum Chromodynamics (QCD) with N_fNf degenerate quarks that have a spatially varying complex mass. It leads to a network of interfaces connected by interface junctions. We use anomaly inflow to constrain these defects. Based on the chiral Lagrangian and the conjectures on the interfaces, characterized by a spatially varying \thetaθ-parameter, we propose a low-energy description of such networks of interfaces. Interestingly, we observe that the operators in the effective field theories on the junctions can carry baryon charges, and their spin and isospin representations coincide with baryons. We also study defects, characterized by spatially varying coupling constants, in 2+1 dimensional Chern-Simons-matter theories and in a 3+1 dimensional real scalar theory.

scholarly journals Effective Field Theories

Particles ◽  
2020 ◽  
Vol 3 (2) ◽  
pp. 245-271 ◽  
Author(s):  
Andrey Grozin
Keyword(s):  
Effective Field Theories ◽  
Degrees Of Freedom ◽  
Effective Field ◽  
Low Energy ◽  
Field Theories ◽  
Alternative View ◽  
Heavy Particles ◽  
Technical Complications ◽  
Effective Theories

This paper represents a pedagogical introduction to low-energy effective field theories. In some of them, heavy particles are “integrated out” (a typical example—the Heisenberg–Euler EFT); in some, heavy particles remain but some of their degrees of freedom are “integrated out” (Bloch–Nordsieck EFT). A large part of these lectures is, technically, in the framework of QED. QCD examples, namely decoupling of heavy flavors and HQET, are discussed only briefly. However, effective field theories of QCD are very similar to the QED case, and there are just some small technical complications: more diagrams, color factors, etc. The method of regions provides an alternative view at low-energy effective theories; this is also briefly introduced.

scholarly journals Power counting and Wilsonian renormalization in nuclear effective field theory

2016 ◽  
Vol 25 (05) ◽  
pp. 1641007 ◽  
Author(s):  
Manuel Pavón Valderrama
Keyword(s):  
Field Theory ◽  
Effective Field Theories ◽  
Effective Field Theory ◽  
Nuclear Physics ◽  
High Energy ◽  
Effective Field ◽  
Power Counting ◽  
Low Energy ◽  
Field Theories ◽  
Nuclear Forces

Effective field theories are the most general tool for the description of low energy phenomena. They are universal and systematic: they can be formulated for any low energy systems we can think of and offer a clear guide on how to calculate predictions with reliable error estimates, a feature that is called power counting. These properties can be easily understood in Wilsonian renormalization, in which effective field theories are the low energy renormalization group evolution of a more fundamental — perhaps unknown or unsolvable — high energy theory. In nuclear physics they provide the possibility of a theoretically sound derivation of nuclear forces without having to solve quantum chromodynamics explicitly. However there is the problem of how to organize calculations within nuclear effective field theory: the traditional knowledge about power counting is perturbative but nuclear physics is not. Yet power counting can be derived in Wilsonian renormalization and there is already a fairly good understanding of how to apply these ideas to non-perturbative phenomena and in particular to nuclear physics. Here we review a few of these ideas, explain power counting in two-nucleon scattering and reactions with external probes and hint at how to extend the present analysis beyond the two-body problem.

scholarly journals Effective field theory calculations of NN → NNπ

2014 ◽  
Vol 23 (04) ◽  
pp. 1430004 ◽  
Author(s):  
Vadim Baru ◽  
Christoph Hanhart ◽  
Fred Myhrer
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Pion Production ◽  
Mass Difference ◽  
Effective Field ◽  
S Wave ◽  
Chiral Effective Field Theory ◽  
Charge Symmetry ◽  
Pion Nucleon ◽  
Scattering Lengths

In this review, we present the recent advances for calculations of the reactions NN → NNπ using chiral effective field theory χEFT. Discussed are the next-to-next-to leading order (N2LO) loop contributions with nucleon and Delta-isobar for near threshold s-wave pion-production. Results of recent experimental pion-production data for energies close to the threshold are analyzed. Several particular applications are discussed: (i) it is shown how the measured charge symmetry (CS) violating pion-production reaction can be used to extract the strong interaction contribution to the proton–neutron mass difference; (ii) the role of NN → NNπ for the extraction of the pion–nucleon scattering lengths from pionic atoms data is illuminated.

scholarly journals Gravitational positivity bounds

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Junsei Tokuda ◽  
Katsuki Aoki ◽  
Shin’ichi Hirano
Keyword(s):  
Dispersion Relation ◽  
Effective Field Theories ◽  
Imaginary Part ◽  
Higher Order ◽  
Effective Field ◽  
Low Energy ◽  
Field Theories ◽  
Loop Level ◽  
Regge Behavior ◽  
Wrong Sign

Abstract We study the validity of positivity bounds in the presence of a massless graviton, assuming the Regge behavior of the amplitude. Under this assumption, the problematic t-channel pole is canceled with the UV integral of the imaginary part of the amplitude in the dispersion relation, which gives rise to finite corrections to the positivity bounds. We find that low-energy effective field theories (EFT) with “wrong” sign are generically allowed. The allowed amount of the positivity violation is determined by the Regge behavior. This violation is suppressed by $$ {M}_{\mathrm{pl}}^{-2}\alpha^{\prime } $$ M pl − 2 α ′ where α′ is the scale of Reggeization. This implies that the positivity bounds can be applied only when the cutoff scale of EFT is much lower than the scale of Reggeization. We then obtain the positivity bounds on scalar-tensor EFT at one-loop level. Implications of our results on the degenerate higher-order scalar-tensor (DHOST) theory are also discussed.

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