4,305 research outputs found

### Emergent Photons and Gravitons:The Problem of Vacuum Structure

We discuss vacuum condensates associated with emergent QED and with torsion,
as well as the possible role of the Kodama wave function in quantum cosmology.Comment: Talk presented at the Fifth Meeting on CPT and Lorentz Symmetry,
University of Indiana, June 28-July 2, 201

### Intersections 2000: What's New in Hadron Physics

Hadron physics is that part of QCD dealing with hadron structure and vacuum
structure, almost all of which is nonperturbative in nature. Some of the open
problems in this field are outlined. We argue that hadron physics is a distinct
subfield, no longer within particle physics, and not at all the same as
classical nuclear physics. We believe that it needs to be better organized, and
that a first step in doing so might be to establish hadron physics as a new
division within the American Physical Society.Comment: Invited Talk at 7th Conference on the Intersections of Particle and
Nuclear Physics, Quebec City, Quebec, Canada, May 22-28, 200

### Hybrid Dirac Fields

Hybrid Dirac fields are fields that are general superpositions of the
annihilation and creation parts of four Dirac spin 1/2 fields,
$\psi^{(\pm)}(x;\pm m)$, whose annihilation and creation parts obey the Dirac
equation with mass $m$ and mass $-m$. We discuss a specific case of such
fields, which has been called ``homeotic.'' We show for this case, as is true
in general for hybrid Dirac fields (except the ordinary fields whose
annihilation and creation parts both obey one or the other Dirac equation),
that (1) any interacting theory violates both Lorentz covariance and causality,
(2) the discrete transformations $\mathcal{C}$, and $\mathcal{CPT}$ map the
pair $\psi_h(x)$ and $\bar{\psi}_h(x)$ into fields that are not linear
combinations of this pair, and (3) the chiral projections of $\psi_h(x)$ are
sums of the usual Dirac fields with masses $m$ and $-m$; on these chiral
projections $\mathcal{C}$, and $\mathcal{CPT}$ are defined in the usual way,
their interactions do not violate $\mathcal{CPT}$, and interactions of chiral
projections are Lorentz covariant and causal. In short, the main claims
concerning ``homeotic'' fields are incorrect.Comment: 10 pages, acknowledgement added, to appear in Phys. Lett.

### Future Directions for QCD

New directions for exploring QCD at future high-energy colliders are
sketched. These include jets within jets, BFKL dynamics, soft and hard
diffraction, searches for disoriented chiral condensate, and doing a better job
on minimum bias physics. The new experimental opportunities include
electron-ion collisions at HERA, a new collider detector at the C0 region of
the TeVatron, and the FELIX initiative at the LHC.Comment: Latex, 6 pages, to be published in the proceedings of the 1996
DPF/DPB Summer Study of New Directions for High Energy Physics, Snowmass, CO,
June 25-July 12, 199

### Standard Model Parameters and the Cosmological Constant

Simple functional relations amongst standard model couplings, including
gravitional, are conjectured. Possible implications for cosmology and future
theory are discussed.Comment: submitted to Physical Review

### Rapidity Gaps in Deep Inelastic Scattering

A simple semiquantitative picture of diffractive electroproduction is
described. Although the diffractive component of $F_2$ is approximately
independent of $Q^2$ and $W^2$, this mechanism is "soft," i.e. it depends upon
large-distance physics and is not readily describable within perturbative QCD.Comment: LaTex 14 pages, 3 figures. To obtain a copy, send e-mail to
[email protected]

### Probability in relativistic quantum mechanics and foliation of spacetime

The conserved probability densities (attributed to the conserved currents
derived from relativistic wave equations) should be non-negative and the
integral of them over an entire hypersurface should be equal to one. To satisfy
these requirements in a covariant manner, the foliation of spacetime must be
such that each integral curve of the current crosses each hypersurface of the
foliation once and only once. In some cases, it is necessary to use
hypersurfaces that are not spacelike everywhere. The generalization to the
many-particle case is also possible.Comment: 9 pages, 3 figures, revised, new references, to appear in Int. J.
Mod. Phys.

### Emergence of Coherent Long Wavelength Oscillations After a Quench: Application to QCD

To model the dynamics of the chiral order parameter in a far from equilibrium
phase transition, we consider quenching in the O(4) linear sigma model. We
argue, and present numerical evidence, that in the period immediately following
the quench long wavelength modes of the pion field are amplified. This results
in large regions of coherent pion oscillations, and could lead to dramatic
phenomenological consequences in heavy ion collisions.Comment: 18 pages, 4 figures included (uuencoded and compressed); uses phyzzx;
PUPT-1389, IASSNS-HEP-93/1

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