scholarly journals John Clive Ward. 1 August 1924—6 May 2000

2021 ◽  
Author(s):  
Norman Dombey
Keyword(s):  
Quantum Electrodynamics ◽  
Particle Physics ◽  
Statistical Physics ◽  
Gauge Theories ◽  
The United States ◽  
Strong Interactions ◽  
Electroweak Theory ◽  
Elementary Particle Physics ◽  
Abdus Salam ◽  
The Uk

John Clive Ward was a theoretical physicist who made important contributions to two of the principal subjects in twentieth-century elementary particle physics: namely, quantum electrodynamics (QED) and electroweak theory. He was an early proponent of the importance of gauge theories in quantum field theory and their use in demonstrating the renormalization of those theories: that is, to remove apparent infinities in calculations. He showed that gauge invariance implies the equality of two seemingly different renormalized quantities in QED, a relationship now called the Ward Identity. This identity can be generalized to more general gauge theories in particle physics and remains a fundamental tool in these theories, which dominate particle theory at the present time. He collaborated with Abdus Salam on the use of gauge theories in strong interactions and in electroweak theory. He also made significant contributions to statistical physics. In 1955 he was recruited by the UK Atomic Weapons Research Establishment at Aldermaston to head the Green Granite section of the theoretical group, which had the task of rederiving the thermonuclear weapon concepts developed by Ulam and Teller in the United States. He spent the years from 1966 to his retirement in 1984 at Macquarie University in Australia.

The Standard Model of Particle Physics

2015 ◽  
Vol 23 (1) ◽  
pp. 36-44 ◽  
Author(s):  
Tom W.B. Kibble
Keyword(s):  
Standard Model ◽  
Quantum Electrodynamics ◽  
Particle Physics ◽  
Gauge Theories ◽  
Personal Perspective ◽  
Electroweak Theory ◽  
Higgs Particle ◽  
Historical Account ◽  
The Standard Model ◽  
Nuclear Interactions

This is a historical account from my personal perspective of the development over the last few decades of the standard model of particle physics. The model is based on gauge theories, of which the first was quantum electrodynamics, describing the interactions of electrons with light. This was later incorporated into the electroweak theory, describing electromagnetic and weak nuclear interactions. The standard model also includes quantum chromodynamics, the theory of the strong nuclear interactions. The final capstone of the model was the Higgs particle discovered in 2012 at CERN. But the model is very far from being the last word; there are still many gaps in our understanding.

scholarly journals Dynamical Symmetries of the H Atom, One of the Most Important Tools of Modern Physics: SO(4) to SO(4,2), Background, Theory, and Use in Calculating Radiative Shifts

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1323 ◽  
Author(s):  
G. Jordan Maclay
Keyword(s):  
Hydrogen Atom ◽  
Quantum Electrodynamics ◽  
Particle Physics ◽  
Bound States ◽  
Integrated Treatment ◽  
Invariance Group ◽  
Elementary Particle Physics ◽  
Background Theory ◽  
Modern Physics ◽  
History Of

Understanding the hydrogen atom has been at the heart of modern physics. Exploring the symmetry of the most fundamental two body system has led to advances in atomic physics, quantum mechanics, quantum electrodynamics, and elementary particle physics. In this pedagogic review, we present an integrated treatment of the symmetries of the Schrodinger hydrogen atom, including the classical atom, the SO(4) degeneracy group, the non-invariance group or spectrum generating group SO(4,1), and the expanded group SO(4,2). After giving a brief history of these discoveries, most of which took place from 1935–1975, we focus on the physics of the hydrogen atom, providing a background discussion of the symmetries, providing explicit expressions for all of the manifestly Hermitian generators in terms of position and momenta operators in a Cartesian space, explaining the action of the generators on the basis states, and giving a unified treatment of the bound and continuum states in terms of eigenfunctions that have the same quantum numbers as the ordinary bound states. We present some new results from SO(4,2) group theory that are useful in a practical application, the computation of the first order Lamb shift in the hydrogen atom. By using SO(4,2) methods, we are able to obtain a generating function for the radiative shift for all levels. Students, non-experts, and the new generation of scientists may find the clearer, integrated presentation of the symmetries of the hydrogen atom helpful and illuminating. Experts will find new perspectives, even some surprises.

scholarly journals A resource efficient approach for quantum and classical simulations of gauge theories in particle physics

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 393
Author(s):  
Jan F. Haase ◽  
Luca Dellantonio ◽  
Alessio Celi ◽  
Danny Paulson ◽  
Angus Kan ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Quantum Monte Carlo ◽  
Quantum Electrodynamics ◽  
Particle Physics ◽  
Gauge Theories ◽  
Hamiltonian Formulation ◽  
Mcmc Methods ◽  
Continuous Limit ◽  
Abelian Gauge ◽  
Gauge Groups

Gauge theories establish the standard model of particle physics, and lattice gauge theory (LGT) calculations employing Markov Chain Monte Carlo (MCMC) methods have been pivotal in our understanding of fundamental interactions. The present limitations of MCMC techniques may be overcome by Hamiltonian-based simulations on classical or quantum devices, which further provide the potential to address questions that lay beyond the capabilities of the current approaches. However, for continuous gauge groups, Hamiltonian-based formulations involve infinite-dimensional gauge degrees of freedom that can solely be handled by truncation. Current truncation schemes require dramatically increasing computational resources at small values of the bare couplings, where magnetic field effects become important. Such limitation precludes one from `taking the continuous limit' while working with finite resources. To overcome this limitation, we provide a resource-efficient protocol to simulate LGTs with continuous gauge groups in the Hamiltonian formulation. Our new method allows for calculations at arbitrary values of the bare coupling and lattice spacing. The approach consists of the combination of a Hilbert space truncation with a regularization of the gauge group, which permits an efficient description of the magnetically-dominated regime. We focus here on Abelian gauge theories and use 2+1 dimensional quantum electrodynamics as a benchmark example to demonstrate this efficient framework to achieve the continuum limit in LGTs. This possibility is a key requirement to make quantitative predictions at the field theory level and offers the long-term perspective to utilise quantum simulations to compute physically meaningful quantities in regimes that are precluded to quantum Monte Carlo.

Quantum chromodynamics: A non-Abelian gauge theory

2019 ◽  
pp. 209-236
Author(s):  
Jean Zinn-Justin
Keyword(s):  
Quantum Chromodynamics ◽  
Particle Physics ◽  
Gauge Theories ◽  
Brst Symmetry ◽  
Parallel Transport ◽  
Strong Interactions ◽  
Asymptotic Freedom ◽  
Abelian Gauge ◽  
Lattice Gauge ◽  
Colour Group

Chapter 13 is devoted to some aspects of quantum chromodynamics (QCD), the part of the Standard Model of particle physics responsible for strong interactions and based on an SU(3) gauge symmetry (the colour group) and gluon gauge fields. First, the geometry of non–Abelian gauge theories, based on parallel transport, is recalled. This leads naturally to the construction of lattice gauge theories with link variables and a plaquette action. The lattice model gives a hint of confinement. QCD is quantized in the temporal of Weyl gauge. Its renormalization involves the BRST symmetry. Its renormalization group properties with asymptotic freedom are emphasized. The infinite degeneracy of the semi–classical ground state can be associated to a winding number. Barrier penetration effects, related to the existence of instantons, lead to the existence of theta vacua and the problem of strong CP violation. Other issues considered are chiral symmetry and axial anomaly.

scholarly journals A bottom-up approach to the strong CP problem

2018 ◽  
Vol 33 (14n15) ◽  
pp. 1850088 ◽  
Author(s):  
J. L. Diaz-Cruz ◽  
W. G. Hollik ◽  
U. J. Saldana-Salazar
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Particle Physics ◽  
Weak Interactions ◽  
Theoretical Description ◽  
Strong Interactions ◽  
Top Down ◽  
Bottom Up ◽  
Elementary Particle Physics ◽  
The Standard Model

The strong CP problem is one of many puzzles in the theoretical description of elementary particle physics that still lacks an explanation. While top-down solutions to that problem usually comprise new symmetries or fields or both, we want to present a rather bottom-up perspective. The main problem seems to be how to achieve small CP violation in the strong interactions despite the large CP violation in weak interactions. In this paper, we show that with minimal assumptions on the structure of mass (Yukawa) matrices, they do not contribute to the strong CP problem and thus we can provide a pathway to a solution of the strong CP problem within the structures of the Standard Model and no extension at the electroweak scale is needed. However, to address the flavor puzzle, models based on minimal SU(3) flavor groups leading to the proposed flavor matrices are favored. Though we refrain from an explicit UV completion of the Standard Model, we provide a simple requirement for such models not to show a strong CP problem by construction.

DIQUARKS IN ELEMENTARY PARTICLE PHYSICS

1989 ◽  
Vol 04 (16) ◽  
pp. 3985-4035 ◽  
Author(s):  
MAREK SZCZEKOWSKI
Keyword(s):  
Elementary Particle ◽  
Particle Physics ◽  
High Energy ◽  
Strong Interactions ◽  
Quantum Field ◽  
High Transverse Momentum ◽  
Elementary Particle Physics ◽  
Proton Production ◽  
Baryon Mass ◽  
Split Field

Many phenomena in elementary particle physics show indications of clustering of two quarks inside baryons. Although the existence of such diquark systems cannot be presently rigorously proven in quantum field theory of strong interactions, phenomenological models require some quark-quark binding to explain effects ranging from the baryon mass spectrum to large pT proton production in high energy pp collisions. This review confronts diquark models predictions with experimental results in low and high transverse momentum hadron-hadron collisions, lepton-nucleon scattering and e+e− annihilations. The recent data from the Split Field Magnet detector on high pT proton production in pp, dd and αα collisions at ISR energies are particularly emphasized.

Quantum field theory (QFT)—built-in combinatorics

2021 ◽  
pp. 17-38
Author(s):  
Adrian Tanasa
Keyword(s):  
Elementary Particle ◽  
Particle Physics ◽  
Statistical Physics ◽  
High Energy Physics ◽  
High Energy ◽  
Field Method ◽  
Graph Polynomials ◽  
Elementary Particle Physics ◽  
Feynman Graphs ◽  
The Standard Model

We briefly exhibit in this chapter the mathematical formalism of QFT, which actually has a non-trivial combinatorial backbone. The QFT setting can be understood as a quantum description of particles and their interactions, a description which is also compatible with Einstein's theory of special relativity. Within the framework of elementary particle physics (or high-energy physics), QFT led to the Standard Model of Elementary Particle Physics, which is the physical theory tested with the best accuracy by collider experiments. Moreover, the QFT formalism successfully applies to statistical physics, condensed matter physics and so on. We show in this chapter how Feynman graphs appear through the so-called QFT perturbative expansion, how Feynman integrals are associated to Feynman graphs and how these integrals can be expressed via the help of graph polynomials, the Kirchhoff–Symanzik polynomials. Finally, we give a glimpse of renormalization, of the Dyson–Schwinger equation and of the use of the so-called intermediate field method. This chapter mainly focuses on the so-called Phi? QFT scalar model.

scholarly journals The Standard Model: how far can it go and how can we tell?

2016 ◽  
Vol 374 (2075) ◽  
pp. 20150260 ◽  
Author(s):  
J. M. Butterworth
Keyword(s):  
Standard Model ◽  
Quantum Electrodynamics ◽  
Particle Physics ◽  
Hadron Collider ◽  
Strong Interactions ◽  
Electroweak Symmetry ◽  
Wide Range ◽  
Successful Prediction ◽  
The Standard Model ◽  
Selection Of

The Standard Model of particle physics encapsulates our current best understanding of physics at the smallest distances and highest energies. It incorporates quantum electrodynamics (the quantized version of Maxwell’s electromagnetism) and the weak and strong interactions, and has survived unmodified for decades, save for the inclusion of non-zero neutrino masses after the observation of neutrino oscillations in the late 1990s. It describes a vast array of data over a wide range of energy scales. I review a selection of these successes, including the remarkably successful prediction of a new scalar boson, a qualitatively new kind of object observed in 2012 at the Large Hadron Collider. New calculational techniques and experimental advances challenge the Standard Model across an ever-wider range of phenomena, now extending significantly above the electroweak symmetry breaking scale. I will outline some of the consequences of these new challenges, and briefly discuss what is still to be found. This article is part of the themed issue ‘Unifying physics and technology in light of Maxwell's equations’.

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