This collection of papers provides a broad view of the development of Lorentz and Poincar‚ invariance and spacetime symmetry throughout the past 100 years. The issues explored in these papers include: (1) formulations of relativity theories in which the speed of light is not a universal constant but which are consistent with the four-dimensional symmetry of the Lorentz and Poincar‚ groups and with experimental results, (2) analyses and discussions by Reichenbach concerning the concepts of simultaneity and physical time from a philosophical point of view, and (3) results achieved by the union of the relativity and quantum theories, marking the beginnings of quantum electrodynamics and relativistic quantum mechanics.Ten of the fundamental experiments testing special relativity are also discussed, showing that they actually support a four-dimensional spacetime based on broad Lorentz and Poincar‚ invariance which is more general than and includes the special theory of relativity. The generalization of the concepts of simultaneity, physical time and the nature of the speed of light within a four-dimensional spacetime framework leads to the conclusion that the symmetries embodied by the special theory of relativity can be realized using only a single postulate ? the principle of relativity for physical laws.

Containing the proceedings of the symposium held by the American Academy of Arts and Sciences to celebrate the 100th anniversary of the birth of Niels Bohr, this collection was first published in 1988. More than any other individual, Bohr was responsible for the development of quantum mechanics and for many of its applications in the pursuit of fundamental understanding of physical reality. In addition to his unique role in the discovery and elucidation of quantum theory, Bohr led the study of the fission of nuclei and was greatly concerned with the impact of the existence of the atomic bomb in the post-World War II era. This unique volume provides a panoramic view of modern physics, some of the philosophical issues associated with quantum theory, the impact of this momentous scientific development on the political circumstance of the Cold War Era and the qualities of a superlative scientist.

This volume reflects the huge and multi-dimensional impact of quantum field theory on the evolution of physics in the 20th century. Dr. Asoke Mitra, editor for the volume and former student and colleague of Freeman Dyson, gathers here a selection of articles in the areas where the impact of QFT has been especially pronounced: from particle physics to string theory and extending to facets of astrophysics and the physics of condensed matter.

The ASI Quarks, Leptons and Beyond, held in Munich from the 5th to the 16th of September 1983 was dedicated to the study of what we now believe are the fundamental building blocks of nature: quarks and leptons. The subject was approached on two levels. On the one hand, a thorough discussion was given of the status of our knowledge of quarks and leptons and their interactions, both from an experi mental and a theoretical standpoint. On the other hand, open problems presented by the so called standard model of quark and lepton interact ions were explored along various ways that lead one beyond this frame work. One of the principal predictions of the standard model is that weak interactions are mediated by heavy Wand Z vector bosons. These particles were discovered in 1983 at CERN and their relevant proper ties were discussed at the ASI by C. Rubbia. Further theoretical predictions concerning these Z and W bosons, yet to be checked by future experimentation, were discussed by G. Altarelli with a view of seeing where the standard model might fail and new physics ensue. The strong interactions of quarks, based on Quantum Chromodynamics (QeD), are presumed to cause the quarks to bind into hadrons. Pro gress in attempts to calculate the observed hadronic spectrum, ab initio, starting from QCD and employing lattice methods were reviewed at the ASI by P. Hasenfratz.

This volume is centered on recent developments in the exploration of hadronic structure through lepton scattering, in the description of hadron physics directly from lattice QCD and non-perturbative QCD models, and in efforts to strengthen the links between these activities. Specific topics that are covered include: parton distribution functions, polarized structure functions, generalized structure functions, nuclear effects, quark-hadron duality, electromagnetic form factors, structure functions and hadron properties from lattice QCD, and QCD models based on the DysonOCoSchwinger equations. Contents: Partonic Structure of Hadrons: Chiral Extrapolation of Lattice Structure Function Calculations (W Detmold); Exclusive Processes at HERMES (N Bianchi); Soft Pion Production Associated with Deeply Virtual Compton Scattering (L Mosse); Spin Structure of Hadrons: Polarized Structure Functions in QCD (J Kodaira); Single Spin Asymmetries and Quark Fragmentation (M Anselmino et al.); Perturbative OCo Nonperturbative QCD Transition: Lepton Scattering and Quark-Hadron Duality Studies at Jlab (R Ent); Estimating Low Energy Model Parameters from Deep Inelastic Scattering (L P Hoyt & A I Signal); Form Factors: Physical Hadron Properties from Lattice Data at Large Quark Masses (A W Thomas); Electromagnetic Interactions in Light Front Dynamics (J -F Mathiot); Nucleon Form Factors in the Covariant Diquark-Quark Model (R Alkofer & M Oettel); Hadron Excitations, Confinement and Chiral Symmetry Breaking: Experimental Studies of the Hadron Spectrum (J Napolitano); The Character of Goldstone Bosons (M B Hecht et al.); Deconfining by Winding (R Hofmann); Small- x Physics and Nuclear Medium Effects: Leading Nucleon Production at HERA (G Levman); Nuclear Medium Effects at HERMES (P di Nezza); Physics Motivation for a Polarized Electron-Ion Collider (J M Cameron & J T Londergan); and other papers. Readership: Theoretical and experimental researchers in nuclear and high energy physics."