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O. W. Greenberg

Publications and source records attributed to O. W. Greenberg.

36 records · Page 2Linked to original sources
arXiv2001

Construction of bosons and fermions out of quons

The quon algebra describes particles, ``quons,'' that are neither fermions nor bosons, using a label $q$ that parametrizes a smooth interpolation between bosons ($q = 1$) and fermions ($q = -1$). Understanding the relation of quons on the one side and bosons or fermions on the other can shed light on the different properties of these two kinds of operators and the statistics which they carry. In particular, local bilinear observables can be constructed from bosons and fermions, but not from quons. In this paper we construct bosons and fermions from quon operators. For bosons, our construction works for $-1 \leq q \leq 1$. The case $q=-1$ is paradoxical, since that case makes a boson out of fermions, which would seem to be impossible. None the less, when the limit $q \to -1$ is taken from above, the construction works. For fermions, the analogous construction works for $-1 \leq q \leq 1$, which includes the paradoxical case $q=1$.

hep-th↗
arXiv2000

Quons in Relativistic Theories Must be Bosons or Fermions

The quon algebra describes particles, ``quons,'' that are neither fermions nor bosons using a label q that parametrizes a smooth interpolation between bosons (q = +1) and fermions (q = -1). We derive ``conservation of statistics'' relations for quons in relativistic theories, and show that in relativistic theories quons must be either bosons or fermions.

hep-th↗
arXiv2000

Theories of violation of statistics

I discuss theories of violations of statistics, including intermediate statistics, parastatistics, parons, and quons. I emphasize quons, which allow small violations of statistics. I analyze the quon algebra and its representations, implications of the algebra including the observables allowed by the superselection rule separating inequivalent representations of the symmetric group, the conservation of statistics rules, and the rule for composite systems of quons. I conclude by raising the question of possible origins of violations of statistics and of the level at which violations should be expected if they exist.

hep-th↗
arXiv2000

Study of a Model of Quantum Electrodynamics

This paper studies the model of the quantum electrodynamics (QED) of a single nonrelativistic electron due to W. Pauli and M. Fierz and studied further by P. Blanchard. This model exhibits infrared divergence in a very simple context. The infrared divergence is associated with the inequivalence of the Hilbert spaces associated with the free Hamiltonian and with the complete Hamiltonian. Infrared divergences that are visible in the perturbative description disappear in the space of the clothed electrons. In this model when the Hamiltonian is expressed in terms of the ``physical'' fields that create the electron together with its cloud of soft photons the variational principle suggested earlier can be applied. At finite time the Heisenberg field of the model acts in the space of the perturbative electron together with a finite number of perturbative photons, while the ``physical'' field can be chosen to act in the space of the exact (``physical'') electron eigenstates together with a finite number of physical photons. The space of the physical (or clothed) electron states can be chosen to be a Fock space.

hep-th↗
arXiv1999

Small Violations of Statistics

There are two motivations to consider statistics that are neither Bose nor Fermi: (1) to extend the framework of quantum theory and of quantum field theory, and (2) to provide a quantitative measure of possible violations of statistics. After reviewing tests of statistics for various particles, and types of statistics that are neither Bose nor Fermi, I discuss quons, particles characterized by the parameter $q$, which permit a smooth interpolation between Bose and Fermi statistics; $q=1$ gives bosons, $q=-1$ gives fermions. The new result of this talk is work by Robert C. Hilborn and myself that gives a heuristic argument for an extension of conservation of statistics to quons with trilinear couplings of the form $\bar{f}fb$, where $f$ is fermion-like and $b$ is boson-like. We showed that $q_f^2=q_b$. In particular, we related the bound on $q_γ$ for photons to the bound on $q_e$ for electrons, allowing the very precise bound for electrons to be carried over to photons. An extension of our argument suggests that all particles are fermions or bosons to high precision.

quant-ph↗
arXiv1999

Quon Statistics for Composite Systems and a Limit on the Violation of the Pauli Principle for Nucleons and Quarks

The quon algebra gives a description of particles, ``quons,'' that are neither fermions nor bosons. The parameter $q$ attached to a quon labels a smooth interpolation between bosons, for which $q = +1$, and fermions, for which $q = -1$. Wigner and Ehrenfest and Oppenheimer showed that a composite system of identical bosons and fermions is a fermion if it contains an odd number of fermions and is a boson otherwise. Here we generalize this result to composite systems of identical quons. We find $q_{composite}=q_{constituent}^{n^2}$ for a system of $n$ identical quons. This result reduces to the earlier result for bosons and fermions. Using this generalization we find bounds on possible violations of the Pauli exclusion principle for nucleons and quarks based on such bounds for nuclei.

quant-ph↗
arXiv1998

The Relation of Constraints on Particle Statistics for Different Species of Particles

Quons are particles characterized by the parameter $q$, which permits smooth interpolation between Bose and Fermi statistics; $q=1$ gives bosons, $q=-1$ gives fermions. In this paper we give a heuristic argument for an extension of conservation of statistics to quons with trilinear couplings of the form $\bar{f}fb$, where $f$ is fermion-like and $b$ is boson-like. We show that $q_f^2=q_b$. In particular, we relate the bound on $q_γ$ for photons to the bound on $q_e$ for electrons, allowing the very precise bound for electrons to be carried over to photons. An extension of this argument suggests that all particles are fermions or bosons to high precision.

hep-th↗
arXiv1998

Variational Principle in the Algebra of Asymptotic Fields

This paper proposes a variational principle for the solutions of quantum field theories in which the ``trial functions'' are chosen from the algebra of asymptotic fields, and illustrates this variational principle in simple cases.

hep-th↗
arXiv1997

Spin-Statistics, Spin-Locality, and TCP: Three Distinct Theorems

I show that the spin-statistics theorem has been confused with another theorem that I call the spin-locality theorem. I also argue that the spin-statistics theorem properly depends on the properties of asymptotic fields which are free fields. In addition, I discuss how ghosts evade both theorems, give the basis of the spin-statistics theorem for fields without asymptotic limits such as quark and gluon fields, and emphasise the weakness of the requirements for the $TCP$ theorem.

hep-th↗
arXiv1996

Bound States in Galilean-Invariant Quantum Field Theory

We consider the nonrelativistic quantum mechanics of a model of two spinless fermions interacting via a two-body potential. We introduce quantum fields associated with the two particles as well as the expansion of these fields in asymptotic ``in'' and ``out'' fields, including such fields for bound states, in principle. We limit our explicit discussion to a two-body bound state. In this context we discuss the implications of the Galilean invariance of the model and, in particular, show how to include bound states in a strictly Galilean-invariant quantum field theory.

hep-ph↗
arXiv1995

Conservation of Statistics and Generalized Grassmann Numbers

Conservation of statistics requires that fermions be coupled to Grassmann external sources. Correspondingly, conservation of statistics requires that parabosons, parafermions and quons be coupled to external sources that are the appropriate generalizations of Grassmann numbers.

hep-ph↗
arXiv1995

COVARIANT SINGLE-TIME BOUND-STATE EQUATION

We derive a system of covariant single-time equations for a two-body bound state in a model of scalar fields $ϕ_1$ and $ϕ_2$ interacting via exchange of another scalar field $χ$. The derivation of the system of equations follows from the Haag expansion. The equations are linear integral equations that are explicitly symmetric in the masses, $m_1$ and $m_2$, of the scalar fields, $ϕ_1$ and $ϕ_2$. We present an approximate analytic formula for the mass eigenvalue of the ground state and give numerical results for the amplitudes for a choice of constituent and exchanged particle masses.

hep-ph↗
arXiv1995

VIRTUES OF THE HAAG EXPANSION IN QUANTUM FIELD THEORY

I survey the use of the Haag expansion as a technique to solve quantum field theories. After an exposition of the asymptotic condition and the Haag expansion, I report the results of applying the Haag expansion to several quantum field theories, including galilean-invariant theories, matter at finite temperature (using the BCS model of superconductivity as an illustrative example), the Nambu--Jona-Lasinio model and the Schwinger model. I conclude with the outlook for further development of this method.

hep-ph↗
arXiv1993

Quons, an interpolation between bose and fermi oscillators

After a brief mention of Bose and Fermi oscillators and of particles which obey other types of statistics, including intermediate statistics, parastatistics, paronic statistics, anyon statistics and infinite statistics, I discuss the statistics of ``quons'' (pronounced to rhyme with muons), particles whose annihilation and creation operators obey the $q$-deformed commutation relation (the quon algebra or q-mutator) which interpolates between fermions and bosons. I emphasize that the operator for interaction with an external source must be an effective Bose operator in all cases. To accomplish this for parabose, parafermi and quon operators, I introduce parabose, parafermi and quon Grassmann numbers, respectively. I also discuss interactions of non-relativistic quons, quantization of quon fields with antiparticles, calculation of vacuum matrix elements of relativistic quon fields, demonstration of the TCP theorem, cluster decomposition, and Wick's theorem for relativistic quon fields, and the failure of local commutativity of observables for relativistic quon fields. I conclude with the bound on the parameter $q$ for electrons due to the Ramberg-Snow experiment.

cond-mat↗
arXiv1993

Color, from baryon spectroscopy to qcd

I review the discovery of the color degree of freedom in hadronic physics, and the developments which led from that discovery to the local gauge theory of color, quantum chromodynamics.

hep-ph↗
arXiv1992

Scaling limit of a non-relativistic model

I calculate the structure function for scattering from the two-body bound state in its lowest level in a non-relativistic model of confined scalar ``quarks'' of masses $m_A$ and $m_B$. The scaling limit in $x={\bf q}^2/2(m_A+m_B)q^0$ exists and is non-vanishing only for the values $x=m_A/(m_A+m_B)$ and $x=m_B/(m_A+m_B)$ which correspond to the fractions of the momentum of the two-body system carried by each of the ``quarks.'' In the scaling limit, the interference from scattering off of the two ``quarks'' vanishes. Thus the scaling limit of this model agrees with the parton picture.

hep-ph↗