Lorentz Covariant Canonical Formalism for Free Massive, Massless and Tachyonic Particles

We construct a consistent Lorentz-covariant canonical formalism for a free massive, massless and tachyonic particle in the framework of the absolute synchronization scheme of clocks. In the case of a massive particle our approach is canonically equivalent to the standard formulation which is not manifestly covariant. The absolute synchronization scheme seems to be the only one we can apply in the case of massless and tachyonic particles.     

Towards a transport theory of the quark-gluon plasma: Infrared divergences and scalar-meson theory

We consider the transport theory of an ultra-relativistic gas of particles. We study infrared divergences which may appear in a naive perturbative treatment in a massless scalar meson theory. We briefly discuss the potential applications of transport theory for ultra-relativistic nuclear collisions.     

A search for hidden variables in the domain of high energy physics

The idea of hidden variable theories, which contests the notion of quantum mechanics being the fundamental principle of nature, is well known and seems to need no introduction. In 1966 such a theory (of a non-local character) was proposed by D. Bohm and J. Bub. We present a scheme in which measured decay processes may constitute an adequate substitute to the original test proposed in 1966 and which until now proved to be realizable only for massless particles. Finally, we consider a specific proposal concerning Tau decays. A preliminary overview of several experimental data sets is presented.     

Vector tadpole graphs in the Coleman-Weinberg model

In the Coleman-Weinberg model (massless scalar quantum electrodynamics), a gauge invariant approximation scheme is obtained by summing vector tadpole graphs to all loop orders. We investigate the influence of this summation on the masses of the scalar and vector particles in the model.     

On the theoretical problems in constructing interactions involving higher-spin massless particles

It is shown that a gauge theory of self-interacting massless spin-3 particles which is analogous to Yang-Mills or the theory of gravity does not exist. A way out may be the existence of an interacting infinite family of massless particles of various spins. The first-order interactions which are possible between such particles show a remarkable structure. This is established by explicit construction. Detailed results are obtained for the possible algebraic structures which one may obtain for gauge theories which are induced from the gauge invariance of free lagrangians.     

带有整体磁单极子的Barriola-Vilenkin黑洞时空中静质量不为零的粒子的量子隧穿辐射

利用量子隧穿方法研究了带有整体磁单极子的Barriola-Vilenkin黑洞时空中静质量不为零的粒子的隧穿辐射，计算出量子隧穿辐射谱与Bekenstein-Hawking熵变有关，且与无质量粒子的出射率具有相同函数形式，所得结果满足幺正性原理. 关键词： Barriola-Vilenkin黑洞 Painlevé坐标 能量守恒 量子隧穿辐射     

Speed of light in non-trivial vacua

We unify all existing results on the change of the speed of low-energy photons due to modifications of the vacuum, finding that it is given by a universal constant times the quotient of the difference of energy densities between the usual and modified vacua over the mass of the electron to the fourth power. Whether photons move faster or slower than c depends only on the lower or higher energy density of the modified vacuum, respectively. Physically, a higher energy density is characterized by the presence of additional particles (real or virtual) in the vacuum whereas a lower one stems from the absence of some virtual modes. We then carry out a systematic study of the speed of propagation of massless particles for several field theories up to two loops on a thermal vacuum. Only low-energy massless particles corresponding to a massive theory show genuine modifications of their speed while remaining massless. All other modifications are mass related, or running mass-related. We also develop a formalism for the Casimir vacuum which parallels the thermal one and check that photons travel faster than c between plates.     

Compton scattering in the Buchholz–Roberts framework of relativistic QED

We consider a Haag–Kastler net in a positive energy representation, admitting massive Wigner particles and asymptotic fields of massless bosons. We show that massive single-particle states are always vacua of the massless asymptotic fields. Our argument is based on the Mean Ergodic Theorem in a certain extended Hilbert space. As an application of this result, we construct the outgoing isometric wave operator for Compton scattering in QED in a class of representations recently proposed by Buchholz and Roberts. In the course of this analysis, we use our new technique to further simplify scattering theory of massless bosons in the vacuum sector. A general discussion of the status of the infrared problem in the setting of Buchholz and Roberts is given.     

Conformal anomalies and massless particle generation in a Fridman universe

The general structure of conformai anomalies of the energy-momentum tensor is established. The energy density of massless particles generated during the cosmological expansion is calculated in the lowest-order perturbation theory. Estimates are made that indicate that the energy density of generated massless particles in the early universe can significantly exceed the energy density of the generated massive particles.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 54–58, August, 1984.We are grateful to E. S. Fradkin, V. P. Frolov, I. V. Tyutin, and B. L. Voronov for useful discussions.     

Noninteraction of Waves in Two-dimensional Conformal Field Theory

In higher dimensional quantum field theory, irreducible representations of the Poincaré group are associated with particles. Their counterpart in two-dimensional massless models are ??waves?? introduced by Buchholz. In this paper we show that waves do not interact in two-dimensional M?bius covariant theories and in- and out-asymptotic fields coincide. We identify the set of the collision states of waves with the subspace generated by the chiral components of the M?bius covariant net from the vacuum. It is also shown that Bisognano-Wichmann property, dilation covariance and asymptotic completeness (with respect to waves) imply M?bius symmetry. Under natural assumptions, we observe that the maps which give asymptotic fields in Poincaré covariant theory are conditional expectations between appropriate algebras. We show that a two-dimensional massless theory is asymptotically complete and noninteracting if and only if it is a chiral M?bius covariant theory.     

Coupling of massless particles to scalar fields

It is investigated whether massless particles can couple to scalar fields in a special-relativistic theory with classical particles. The only possible obvious theory which is invariant under Lorentz transformationsand reparametrization of the affine parameter leads to trivial trajectories (straight lines) for the massless case, and also the investigation of the masslesslimit of the massive theory shows that there is no influence of the scalar field on the limiting trajectories. On the other hand, in contrast to this result, it is shown that massive particlesare influence by the scalar field in this theory even in the ultrarelativistic limit.     

A class of field theories in two-dimensional space-time with aU 1×U 1 symmetry

The derivative coupling of massless pseudoscalar neutral particles with a charged spinor field in two-dimensional space-time is reduced to a self-interacting spinor field and a free pseudoscalar field.More generally, it is shown that any given local field theory with a conserved vector current and without massless particles can be extended to a local theory with an additional pseudoscalar field and with aU ₁×U ₁ symmetry.     

Dual models for non-hadrons

The possibility of describing particles other than hadrons (leptons, photons, gauge bosons, gravitons, etc.) by a dual model is explored. The Virasoro-Shapiro model is studied first, interpreting the massless spin-two state of the model as a graviton. We prove that in the limit of zero slope (with g_vs²α′ held fixed) one obtains the Einstein theory of gravitation accompanied by a massless scalar field. Next, the Veneziano model is studied for small slope as an expansion in powers of α′. It is known from previous work that the zeroth order term is precisely the Yang-Mills theory of a multiplet of massless vector bosons. We show that there are order α′ terms arising both from the dual tree and loop graphs. The former constitutes a relatively unimportant modification of the Yang-Mills theory, whereas the latter involves the coupling of the massless scalar and graviton states of the Virasoro-Shapiro model. Thus one may take the point of view that gravity arises as a unitarization effect in a dual unified theory of electromagnetism and weak interactions. In order to obtain the correct values for the electric charge and Newton's constant it is necessary that α′ ? 10^?34 GeV^?2 The coupling of massless scalar states is also studied.     

Non-commutative Geometry in Massless and Massive Particles

In this paper, we study the symmetries of massless and massive particles action. By considering the non-commutative space-time, we find appropriate non-commutative relation for relativistic particles which leaves invariant the non-commutative Minkowski space-time. We show that non-commutativity break the scale and conformal invariance in massless and massive action. So, in non-commutative space-time the massless and massive particles have same symmetry.     

Proof of Chiral Symmetry Breaking and Persistent Mass Condition in Vector- Like Gauge Theory

We give the details of rigorous proof of some mass inequalitiee in a vector-like gauge theory based on any simple group G. These mass inequalitiee lead to the conclusions that in auch a theory the chiral symmetries associated with all G representations of quarks must be spontaneously broken, and the persistent mass condition ie justified for any composite particles when the vacuum angle is zero or massless quarks exist.     

Renormalization group functions for the radiative symmetry breaking scheme

We obtain the renormalization group (RG) functions for the massless scalar field theory where symmetry breaking occurs radiatively. After obtaining the effective potential for the radiative symmetry breaking scheme by finite transformations for the classical field and coupling constant, we obtain the corresponding RG functions from that of the minimal subtraction (MS) scheme.     

Mass spectrum of the M4×SD solution in Euler invariant type higher derivative gravity

The mass spectrum is computed in Euler invariant type higher derivative gravity theory in the case that the space-time is dimensionally reduced to the four-dimensional Minkowski space × D-dimensional sphere. It is shown at the linearized level that after the compactification there appear massless gravitons, massive spin-two particles, massless vectors and one massive scalar mode. All the vectors are massless and the masses of massive spin-two particles are proportional to the S^D eigenvalues of the laplacian. Classical stability is shown to depend only on three parameters.     

The Adler condition and high energy bounds on massless particle total cross sections

We study the problem of deriving high energy bounds on total cross sections for processes in which massless particles can participate. We are able to prove such bounds given the following assumptions 1) Mandelstam analyticity 2) polynomial boundedness 3) smoothness 4) Adler's condition for massless pions or analogous conditions for other massless particles such as neutrinos. The resulting bound is that total cross sections are constant up to powers of logarithims of the energy.     

Klein Paradox and Disorder-Induced Delocalization of Dirac in Quasiparticles in One-Dimensional Systems

Dirac particle penetration is studied theoretically with Dirac equation in one-dimensional systems. We investigate a one-dimensional system with N barriers where both barrier height and well width are constants randomlydistributed in certain range. The one-parameter scaling theory for nonrelativistic particles is still valid for massive Dirac particles. In the same disorder sample, we find that the localization length of relativistic particles is always larger than that of nonrelativistic particles and the transmission coefficient related to incident particle in both cases fits the form T ∽ exp(-α_L). More interesting, massless relativistic particles are entirely delocalized no matter how big the energy of incident particles is.     

Optical theorem in curved space-time quantum field theory

A structural analysis is given of the optical theorem in theS-matrix approach to mutually interacting quantum fields in classical Robertson-Walker universes. As a case study, theφψ ²-interaction of conformally coupled massive (φ) and massless (φ) Klein-Gordon particles is studied. Based on the outgoing massless particles as indicator configuration, the physical interpretation is reduced to the corresponding added-up probabilities. Several examples are discussed in an in-in scheme which has the advantage that only a few non-Minkowskian in-in Feynman diagrams are involved.