scholarly journals About coupling constant singularities in quantum electrodynamics

1979 ◽  
Vol 80 (3) ◽  
pp. 236-238 ◽  
Author(s):  
Christof Litwin
Keyword(s):  
Quantum Electrodynamics ◽  
Coupling Constant

scholarly journals SOME COMMENTS ON THE DIVERGENCE OF PERTURBATION SERIES IN QUANTUM ELECTRODYNAMICS

2006 ◽  
Vol 21 (14) ◽  
pp. 1161-1166
Author(s):  
MOFAZZAL AZAM
Keyword(s):  
Perturbation Theory ◽  
Quantum Electrodynamics ◽  
Perturbation Series ◽  
Coupling Constant

It has been argued by Dyson that the perturbation theory in coupling constant in QED cannot be convergent. We find that similar albeit slightly different arguments lead to the divergence of the series of 1/N f expansion in QED.

scholarly journals MASS RENORMALIZATION IN NON-RELATIVISTIC QUANTUM ELECTRODYNAMICS WITH SPIN ½

2007 ◽  
Vol 19 (04) ◽  
pp. 405-454 ◽  
Author(s):  
F. HIROSHIMA ◽  
K. R. ITO
Keyword(s):  
Effective Mass ◽  
Explicit Form ◽  
Quantum Electrodynamics ◽  
Relativistic Quantum ◽  
Spin Interaction ◽  
Bare Mass ◽  
Coupling Constant ◽  
Mass Renormalization ◽  
Ultraviolet Cutoff ◽  
Constant E

The effective mass m eff of the Pauli–Fierz Hamiltonian with ultraviolet cutoff Λ and the bare mass m in non-relativistic quantum electrodynamics (QED) with spin ½ is investigated. Analytic properties of m eff in coupling constant e are shown. Let us set [Formula: see text]. The explicit form of constant a2(Λ/m) depending on Λ/m is given. It is shown that the spin interaction enhances the effective mass and that there exist strictly positive constants c1 and c2 such that [Formula: see text] In particular though it is known that a1(Λ/m) diverge log (Λ/m) as Λ → ∞, a2(Λ/m) does not diverge as ± [ log (Λ/m)]2 but -(Λ/m)2.

Real and virtual processes in quantum electrodynamics

1952 ◽  
Vol 48 (4) ◽  
pp. 640-651 ◽  
Author(s):  
J. Hamilton
Keyword(s):  
Matrix Element ◽  
Power Series ◽  
Quantum Electrodynamics ◽  
Coupling Constant ◽  
Threshold Behaviour ◽  
Physical Processes ◽  
Matrix Formulation ◽  
The Matrix ◽  
Multiple Integrals ◽  
Analytic Behaviour

The S-matrix formulation of quantum electrodynamics, as developed by Feynman (3) and Dyson (1), expresses the matrix element for any process as a power series in the coupling constant, the coefficients of the series being, in general, rather complicated multiple integrals. These integrals contain singularities in their integrands, and in certain circumstances the coincidence of such singularities gives the S-matrix a non-analytic behaviour as a function of, for example, the total energy. The threshold behaviour of the S-matrix in the neighbourhood of energy values at which this phenomenon occurs has been investigated by Eden (2), who shows that the non-analytic behaviour is connected with the possible commencement of new physical processes, such as the creation of a particle.

THE WEAK INTERACTION: ITS HISTORY AND IMPACT ON PHYSICS

2001 ◽  
Vol 16 (22) ◽  
pp. 3633-3658 ◽  
Author(s):  
T. D. LEE
Keyword(s):  
Field Theory ◽  
Quantum Electrodynamics ◽  
Particle Physics ◽  
Transition Period ◽  
Weak Interactions ◽  
Coupling Constant ◽  
Β Decay ◽  
Fermi Interaction ◽  
Modern Period ◽  
History Of

It is a pleasure and an honor for me to give this lecture in honor of Oscar Klein who made major contributions to field theory, quantum electrodynamics and particle physics, including weak interactions. He was the first one to observe that the μ decay and the β decay could be described by the same interaction with the same coupling constant; this led to the discovery of the Universal Fermi Interaction. Perhaps I should begin my discussion of the history of weak interactions by separating it into three periods: (1) Classical Period, 1898–1949. (2) Transition Period, 1949–1956. (3) Modern Period, 1956–.

GAUGE INVARIANT STUDY OF THE STRONG COUPLING PHASE OF MASSLESS QUANTUM ELECTRODYNAMICS

1990 ◽  
Vol 05 (09) ◽  
pp. 1789-1800 ◽  
Author(s):  
M. UKITA ◽  
M. KOMACHIYA ◽  
R. FUKUDA
Keyword(s):  
Strong Coupling ◽  
Quantum Electrodynamics ◽  
Chiral Symmetry Breaking ◽  
Renormalization Scheme ◽  
Gauge Parameter ◽  
Coupling Constant ◽  
Critical Coupling ◽  
Gauge Invariant ◽  
Coupling Phase ◽  
Massless Quantum

The strong coupling phase of massless Quantum Electrodynamics is studied in a gauge invariant way. The formalism is given in which the order parameter of the chiral symmetry breaking is calculated through the vacuum polarization diagrams. Applying this method, the critical coupling constant is shown to exist that is independent of the gauge parameter but is now dependent on the ratio of the two kinds of cutoff. Implication of this new parameter on the renormalization scheme in the strong coupling phase is discussed.

scholarly journals Quantum Algorithms for Simulating the Lattice Schwinger Model

Quantum ◽  
2020 ◽  
Vol 4 ◽  
pp. 306 ◽  
Author(s):  
Alexander F. Shaw ◽  
Pavel Lougovski ◽  
Jesse R. Stryker ◽  
Nathan Wiebe
Keyword(s):  
Quantum Electrodynamics ◽  
Quantum Computer ◽  
Fault Tolerant ◽  
Quantum Algorithms ◽  
Gauge Field Theories ◽  
Coupling Constant ◽  
Schwinger Model ◽  
Pair Density ◽  
Trotter Formula ◽  
Better Than

The Schwinger model (quantum electrodynamics in 1+1 dimensions) is a testbed for the study of quantum gauge field theories. We give scalable, explicit digital quantum algorithms to simulate the lattice Schwinger model in both NISQ and fault-tolerant settings. In particular, we perform a tight analysis of low-order Trotter formula simulations of the Schwinger model, using recently derived commutator bounds, and give upper bounds on the resources needed for simulations in both scenarios. In lattice units, we find a Schwinger model on N/2 physical sites with coupling constant x−1/2 and electric field cutoff x−1/2Λ can be simulated on a quantum computer for time 2xT using a number of T-gates or CNOTs in O~(N3/2T3/2xΛ) for fixed operator error. This scaling with the truncation Λ is better than that expected from algorithms such as qubitization or QDRIFT. Furthermore, we give scalable measurement schemes and algorithms to estimate observables which we cost in both the NISQ and fault-tolerant settings by assuming a simple target observable–the mean pair density. Finally, we bound the root-mean-square error in estimating this observable via simulation as a function of the diamond distance between the ideal and actual CNOT channels. This work provides a rigorous analysis of simulating the Schwinger model, while also providing benchmarks against which subsequent simulation algorithms can be tested.

scholarly journals Dark Matter Axions, Non-Newtonian Gravity and Constraints on Them from Recent Measurements of the Casimir Force in the Micrometer Separation Range

Universe ◽  
2021 ◽  
Vol 7 (9) ◽  
pp. 343
Author(s):  
Galina L. Klimchitskaya ◽  
Vladimir M. Mostepanenko
Keyword(s):  
Dark Matter ◽  
Quantum Electrodynamics ◽  
Casimir Force ◽  
Interaction Strength ◽  
Newtonian Gravity ◽  
Yukawa Interaction ◽  
Coupling Constant ◽  
Differential Measurement ◽  
Type Interaction ◽  
Coated Surfaces

We consider axionlike particles as the most probable constituents of dark matter, the Yukawa-type corrections to Newton’s gravitational law and constraints on their parameters following from astrophysics and different laboratory experiments. After a brief discussion of the results by Prof. Yu. N. Gnedin in this field, we turn our attention to the recent experiment on measuring the differential Casimir force between Au-coated surfaces of a sphere and the top and bottom of rectangular trenches. In this experiment, the Casimir force was measured over an unusually wide separation region from 0.2 to 8μm and compared with the exact theory based on first principles of quantum electrodynamics at nonzero temperature. We use the measure of agreement between experiment and theory to obtain the constraints on the coupling constant of axionlike particles to nucleons and on the interaction strength of a Yukawa-type interaction. The constraints obtained on the axion-to-nucleon coupling constant and on the strength of a Yukawa interaction are stronger by factors of 4 and 24, respectively, than those found previously from gravitational experiments and measurements of the Casimir force but weaker than the constraints following from a differential measurement where the Casimir force was nullified. Some other already performed and planned experiments aimed at searching for axions and non-Newtonian gravity are discussed, and their prospects are evaluated.

SIMULTANEOUS CREATION OF ELECTRON–POSITRON PAIRS AND PHOTONS IN ROBERTSON–WALKER UNIVERSES WITH STATICALLY BOUNDED EXPANSION

1992 ◽  
Vol 07 (12) ◽  
pp. 2695-2712 ◽  
Author(s):  
K.-H. LOTZE
Keyword(s):  
Quantum Electrodynamics ◽  
Particle Creation ◽  
Conformally Flat ◽  
Coupling Constant ◽  
Zeroth Order ◽  
Attenuation Effect ◽  
Interacting Particle ◽  
Electron Positron ◽  
Electrons And Positrons ◽  
Bounded Expansion

We present, based upon quantum electrodynamics in Robertson–Walker flat universes, a thorough analysis of the creation of mutually interacting electron–positron pairs and photons from vacuum. Therefore we discuss at least qualitatively all processes contributing to the number densities of created particles up to the second order in the coupling constant. For two particular expansion laws with Minkowskian in respectively in and out regions, we obtain exact solutions to the Dirac equation and investigate in detail the process of simultaneous creation of electron–positron pairs and photons and the related attenuation effect for fermionic particles. This is done for electrons and positrons which have nonrelativistic momenta at Compton time in rapidly expanding universes. The results are compared with the zeroth-order creation of electron–positron pairs. Despite being smaller by a factor of roughly [Formula: see text], the interacting-particle creation is important mainly as a source of photons even in conformally flat universes.

PHASE SHIFT AND ABSORBED PROBABILITY OF PHOTONS IN A SINGLE ATOM HIGH Q CAVITY ANALYZED BY SUPERSYMMETRY

2002 ◽  
Vol 16 (26) ◽  
pp. 981-990
Author(s):  
XIAN-TING LIANG
Keyword(s):  
Phase Shift ◽  
Quantum Computation ◽  
Quantum Electrodynamics ◽  
Cavity Quantum Electrodynamics ◽  
Single Atom ◽  
Stable Phase ◽  
Coupling Constant ◽  
Cavity Field ◽  
High Q

In this paper, we investigate the phase shift and absorbed probability of photons in a single atom high Q cavity. It is shown that by adjusting the coupling constant of interaction between atom and cavity field we can obtain a large, stable phase shift with low absorption of photons, which is needed by a qubit for quantum computation. Cavity quantum electrodynamics (QED) and supersymmetry are used in the analysis.

scholarly journals QUANTUM ELECTRODYNAMICS AND CHROMODYNAMICS TREATED THROUGH THOMPSON'S APPROACH

2006 ◽  
Vol 21 (18) ◽  
pp. 3809-3824 ◽  
Author(s):  
CLÁUDIO NASSIF ◽  
P. R. SILVA
Keyword(s):  
Quantum Electrodynamics ◽  
Heuristic Method ◽  
Critical Dimension ◽  
Step Function ◽  
Quark Condensate ◽  
Energy Scale ◽  
Field Theories ◽  
Coupling Constant ◽  
Running Coupling ◽  
Running Coupling Constant

In this work we apply Thompson's method (of the dimensions and scales) to study some features of the Quantum Electrodynamics and Chromodynamics. This heuristic method can be considered as a simple and alternative way to the Renormalization Group approach and when applied to QED-Lagrangian is able to obtain in a first approximation both the running coupling constant behavior of α(μ) and the mass m(μ). The calculations are evaluated only at dc = 4, where dc is the upper critical dimension of the problem, so that we obtain the logarithmic behavior both for the coupling α and the excess of mass Δm on the energy scale μ. Although our results are well known in the vast literature of field theories, the advantage of Thompson's method, beyond its simplicity is that it is able to extract directly from QED-Lagrangian the physical (finite) behavior of α(μ) and m(μ), bypassing hard problems of divergences which normally appear in the conventional renormalization schemes applied to field theories like QED. Quantum Chromodynamics (QCD) is also treated by the present method in order to obtain the quark condensate value. Besides this, the method is also able to evaluate the vacuum pressure at the boundary of the nucleon. This is done by assumming a step function behavior for the running coupling constant of the QCD, which fits nicely to some quantities related to the strong interaction evaluated through the MIT-bag model.

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