scholarly journals Where have all the Goldstone bosons gone?

2014 ◽  
Vol 29 (09) ◽  
pp. 1450046 ◽  
Author(s):  
G. S. Guralnik ◽  
C. R. Hagen
Keyword(s):  
Vector Meson ◽  
Gauge Theories ◽  
Broken Symmetry ◽  
Goldstone Theorem ◽  
Massive Vector ◽  
Longitudinal Modes ◽  
Goldstone Bosons ◽  
Physical Spectrum ◽  
Covariant Gauge

According to a commonly held view of spontaneously broken symmetry in gauge theories, troublesome Nambu–Goldstone bosons are effectively eliminated by turning into longitudinal modes of a massive vector meson. This note shows that, this is not in fact, a consistent view of the role of Nambu–Goldstone bosons in such theories. These particles necessarily appear as gauge excitations, whenever they are formulated in a manifestly covariant gauge. The radiation gauge provides therefore the dual advantage of circumventing the Goldstone theorem and making evident the disappearance of these particles from the physical spectrum.

Hamiltonian lattice gauge theories and the role of longitudinal modes

1984 ◽  
Vol 81 (3) ◽  
pp. 626-632
Author(s):  
S. Ryang ◽  
T. Saito ◽  
K. Shigemoto
Keyword(s):  
Gauge Theories ◽  
Longitudinal Modes ◽  
Lattice Gauge ◽  
Hamiltonian Lattice ◽  
Lattice Gauge Theories

scholarly journals Omega vs. pi, and 6d anomaly cancellation

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Joe Davighi ◽  
Nakarin Lohitsiri
Keyword(s):  
Gauge Theories ◽  
Necessary Conditions ◽  
Homotopy Groups ◽  
Mapping Torus ◽  
Anomaly Cancellation ◽  
Global Anomaly ◽  
Gauge Anomalies ◽  
Local Anomalies ◽  
Dimensional Mapping

Abstract In this note we review the role of homotopy groups in determining non-perturbative (henceforth ‘global’) gauge anomalies, in light of recent progress understanding global anomalies using bordism. We explain why non-vanishing of πd(G) is neither a necessary nor a sufficient condition for there being a possible global anomaly in a d-dimensional chiral gauge theory with gauge group G. To showcase the failure of sufficiency, we revisit ‘global anomalies’ that have been previously studied in 6d gauge theories with G = SU(2), SU(3), or G2. Even though π6(G) ≠ 0, the bordism groups $$ {\Omega}_7^{\mathrm{Spin}}(BG) $$ Ω 7 Spin BG vanish in all three cases, implying there are no global anomalies. In the case of G = SU(2) we carefully scrutinize the role of homotopy, and explain why any 7-dimensional mapping torus must be trivial from the bordism perspective. In all these 6d examples, the conditions previously thought to be necessary for global anomaly cancellation are in fact necessary conditions for the local anomalies to vanish.

scholarly journals K0SΣ0 photoproduction at the BGO-OD experiment

2020 ◽  
Vol 241 ◽  
pp. 01009
Author(s):  
Katrin Kohl ◽  
Stefan Alef ◽  
Patrick Bauer ◽  
Reinhard Beck ◽  
Alessandro Braghieri ◽  
...  
Keyword(s):  
Vector Meson ◽  
Momentum Transfer ◽  
Cross Section ◽  
Photon Beam ◽  
Bremsstrahlung Photon ◽  
Meson Photoproduction ◽  
Accelerator Facility ◽  
Transfer Processes

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremsstrahlung photon beam to investigate the excitation structure of the nucleon via meson photoproduction. The setup with a BGO calorimeter surrounding the target and an open dipole spectrometer covering the for ward region is ideally suited for investigating low momentum transfer processes, in particular in strangeness photoproduction. The associated photoproduction of K0S and hyperons is essential to understand the role of K* exchange mech anisms. A cusp-like structure observed in the yp → K0SΣ+ reaction at the K* threshold is described by models including dynamically generated resonances from vector meson-baryon interactions. Such interactions are pre dicted to give a peak like structure in K0SΣ0 photoproduction off the neutron. A very preliminary cross section is determined and compared to the prediction, the results appear to support the model

Spontaneously Broken Symmetries

2021 ◽  
pp. 287-303
Author(s):  
J. Iliopoulos ◽  
T.N. Tomaras
Keyword(s):  
Phase Transitions ◽  
Vector Field ◽  
Quantum Physics ◽  
Goldstone Boson ◽  
Internal Symmetry ◽  
Higgs Mechanism ◽  
Broken Symmetry ◽  
Massive Vector ◽  
Broken Symmetries ◽  
Gauge Symmetries

The phenomenon of spontaneous symmetry breaking is a common feature of phase transitions in both classical and quantum physics. In a first part we study this phenomenon for the case of a global internal symmetry and give a simple proof of Goldstone’s theorem. We show that a massless excitation appears, corresponding to every generator of a spontaneously broken symmetry. In a second part we extend these ideas to the case of gauge symmetries and derive the Brout–Englert–Higgs mechanism. We show that the gauge boson associated with the spontaneously broken generator acquires a mass and the corresponding field, which would have been the Goldstone boson, decouples and disappears. Its degree of freedom is used to allow the transition from a massless to a massive vector field.

Nonlinear Realizations. I. The Role of Goldstone Bosons

1969 ◽  
Vol 184 (5) ◽  
pp. 1750-1759 ◽  
Author(s):  
Abdus Salam ◽  
J. Strathdee
Keyword(s):  
Goldstone Bosons ◽  
Nonlinear Realizations
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