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Gauge theories brought about a profound revolution in the way physicists think about the fundamental forces. It is this revolution that is the subject of Sheldon Lee Glashow’s essay.

Physics has ancient beginnings in the Greek period, in the work of Democritus of Abdera, father of atomic theory, and Euclid from Alexandria, generator of the first axiomatic system ever conceived.

Sheldon Lee Glashow (Shelly to his friends) is not just your friendly-neighborhood run-of-the-mill Nobel laureate. He will join the other great scientists who stand upon the shoulders of giants.

We discuss a class of models in which CP is violated softly in a heavy sector adjoined to the standard model. Heavy-sector loops produce the observed CP violation in kaon physics, yielding a tiny and probably undetectable value for $\epsilon^\prime$. All other CP-violating parameters in the effective low-energy standard model, including the area of the unitarity triangle and $\bar\theta$, are finite, calculable and can be made very small. The leading contribution to $\bar\theta$ comes from a four-loop graph. These models offer a natural realization of superweak CP violation and can resolve the strong CP puzzle. In one realization of this idea, CP is violated in the mass matrix of heavy majorana neutrinos., Comment: 12 pages, embedded figures - this version was further revised after acceptance for publication

Recent evidence for oscillations of atmospheric neutrinos at Super-Kamiokande suggest, in the simplest see-saw interpretation, neutrino masses such that `just so' vacuum oscillations can explain the solar neutrino deficit. Super-K solar neutrino data provide preliminary support for this interpretation. We describe how the just-so signal---an energy dependent seasonal variation of the event rate, might be detected within the coming years and provide general arguments constraining the sign of the variation. The expected variation at radiochemical detectors may be below present sensitivity, but a significant modulation in the $^7$Be signal could shed light on the physics of the solar core---including a direct measure of the solar core temperature., Comment: 4 pages, revtex, 4 ps figs: new refs added, and Super-K energy resolution function incorporated

We ask whether the universe can be a patchwork consisting of distinct regions of matter and antimatter. We demonstrate that, after recombination, it is impossible to avoid annihilation near regional boundaries. We study the dynamics of this process to estimate two of its signatures: a contribution to the cosmic diffuse gamma-ray background and a distortion of the cosmic microwave background. The former signal exceeds observational limits unless the matter domain we inhabit is virtually the entire visible universe. On general grounds, we conclude that a matter-antimatter symmetric universe is empirically excluded., 28 pages, 5 figures, uses graphicx package; updated for Ap. J. version. Includes additional discussion of turbulence

We demonstrate the equoivalence of two seemingly disparate dynamical systems. One consits of three hard rods sliding along a frictionless ring and making elastic collisions. The other consists of one ball moving on a frictionless triangular table with elastic rails. Several applications of this result are discussed.

We discuss the theory and phenomenology of decays of a leptophobic $U(1)_\X$ gauge boson $X$, such as has been proposed to explain the alleged deviations of $R_b$ and $R_c$ from standard model predictions. If the scalars involved in the breaking of the $SU(2)\times U(1)$ symmetry are sufficiently light, $X$ will sometimes decay into a charged (or neutral) scalar along with an oppositely-charged $W$ (or $Z$). These decay modes could yield clean signals for the leptophobic gauge bosons at hadron colliders and provide an interesting window into the Higgs sector of the theory., Comment: LATEX, 12 pages with PICTEX figures

Most theoretical physicists rely on interactions with others to stay abreast of theoretical and experimental advances. In classrooms and seminars, on blackboards and napkins, they exchange and clarify ideas with colleagues and students. Rare is the theoretical physicist who makes repeated and varied contributions apart from the throng; rarer still is one who not only contributes but also sets standards and priorities singlehandedly. Julian Seymour Schwinger, who died 16 July 1994 at the age of 76, was such an individual. Gentle but steadfastly independent, quiet but dramatically eloquent, self‐taught and self‐propelled, brilliant and prolific, Schwinger remained active and productive until his death. His ideas, discoveries and techniques pervade all areas of theoretical physics.

This chapter looks back at some of the most memorable achievements in high-energy physics during the 50 years spanning CERN's PS and LHC.

It is shown how, in a class of models, the sign of the baryon number of the universe can be related to CP violation in neutrino oscillation experiments., 3 pages LaTeX

We propose that dark matter is made of CHAMP's, charged massive particles that survive annihilation in the early Universe. We constrain champs to be matter-antimatter symmetric, to provide critical mass density, and to constitute the non-baryonic halo of galaxies such as ours. We show that the window of allowed champ mass extends from 20 to 1000 TeV. Champs of charge + 1 should now appear as super-heavy isotopes of hydrogen. While some of their antiparticles could bind to 4He nuclei somewhat after primordial nucleosynthesis (also to appear today in the disguise of super-heavy hydrogen), we argue that negative champs overwhelmingly bind to protons to pose as super-heavy stable neutrons. En route to detectors, these bound champs suffer nuclear reactions that change their ultimate appearance. By the time they come to rest, negative champs have recombined with larger nuclei to form various super-heavy isotopes. We discuss how and where to search for relic champs.

We assume there to be precisely three left-handed neutrino states whose Majorana masses are generated by an unspecified mechanism. Were CP conserved, the symmetric neutrino mass matrix M would be real and all six of its distinct entries could be experimentally determined. But CP is not conserved so that M is likely to be complex. As a result, not all nine of its convention-independent real parameters can be determined without an appeal to theory. Thus we examine the possibility that a restricted class of neutrino mass matrices may suffice to describe current data, namely those complex symmetric matrices several of whose entries vanish. We find that there are seven acceptable textures with two independent zeroes, and we explore their contrasting phenomenological implications. Textures with more than two independent zeroes appear to be excluded by experiment., Comment: Version to appear in PLB

Recent observations of solar neutrinos along with decades of data from the chlorine experiment seem to be converging on an explanation of the sun's neutrino deficit. Electron and muon neutrinos with Majorana masses ∼10-3 eV/c2 are subject to MSW suppression as they traverse the sun. However, Simpson's studies of s-decay spectra show that νe mixes with a Dirac neutrino (presumably ντ) of a consmologically nettlesome mass. We propose a simple modification of the singlet majoron hypothesis that accounts for these results yet remains in accord with known constraints from particle physics and cosmological theory. Maximal ντ oscillations into a sterile state are predicted.

Working in the framework of three chiral neutrinos with Majorana masses, we investigate a scenario first realized in an explicit model by Zee: that the neutrino mass matrix is strictly off-diagonal in the flavor basis, with all its diagonal entries precisely zero. This CP-conserving ansatz leads to two relations among the three mixing angles $(\theta_1, \theta_2, \theta_3)$ and two squared mass differences. We impose the constraint $|m_3^2 - m_2^2| \gg |m^2_2 - m_1^2|$ to conform with experiment, which requires the $\theta_i$ to lie nearby one of four 1-parameter domains in $\theta$-space. We exhibit the implications for solar and atmospheric neutrino oscillations in each of these cases. A unique version of the Zee {\it ansatz} survives confrontation with experimental data, one which necessarily involves maximal just-so vacuum oscillations of solar neutrinos., Comment: 7 pages, harvmac, typo corrected, ref. added, text modified

We develop a perturbative framework with which to discuss departures from exact Lorentz invariance and explore their potentially observable ramifications. Tiny non-invariant terms introduced into the standard model Lagrangian are assumed to be renormalizable (dimension $\le 4$), invariant under $SU(3)\otimes SU(2)\otimes U(1)$ gauge transformations, and rotationally and translationally invariant in a preferred frame. There are a total of 46 independent TCP-even perturbations of this kind, all of which preserve anomaly cancellation. They define the energy-momentum eigenstates and their maximal attainable velocities in the high-energy limit. The effects of these perturbations increase rapidly with energy in the preferred frame, more rapidly than those of TCP-odd perturbations. Our analysis of Lorentz-violating kinematics reveals several striking new phenomena that are relevant both to cosmic-ray physics ({\it e.g.,} by undoing the GZK cutoff) and neutrino physics ({\it e.g.,} by generating novel types of neutrino oscillations). These may lead to new and sensitive high-energy tests of special relativity., Comment: 33 pages, uses harvmac. This 2nd revision corrects two typos, an error in the Appendix, and includes further acknowledgements

We posit a second massless photon, uncoupled to known forms of matter but undergoing Lorentz non-invariant velocity mixing with ordinary photons. Our speculation within a speculation suffers from the sin of implausibility but enjoys the virtue of verifiability. To avoid unacceptable distortion of the well-measured microwave background spectrum, the velocity difference of the photons cannot exceed $\sim10^{-32} c$. Stronger constraints (or observable effects!) can arise from optical measurements of distant sources., Comment: 4 pages, TEX with harvmac macros

Recent data lead us to a simple and intriguing form of the neutrino mass matrix. In particular, we find solar neutrino oscillations to be nearly maximal (and rule out the small-angle MSW explanation of solar neutrino observations) if relic neutrinos comprise at least one~percent of the critical mass density of the universe., Comment: 7 pages, harvmac, minor changes and new references in revised version

Searches for anisotropies due to Earth's motion relative to a preferred frame -- modern versions of the Michelson-Morley experiment -- provide precise verifications of special relativity. We describe other tests, independent of this motion, that are or can become even more sensitive. The existence of high-energy cosmic rays places strong constraints on Lorentz non-invariance. Furthermore, if the maximum attainable speed of a particle depends on its identity, then neutrinos, even if massless, may exhibit flavor oscillations. Velocity differences far smaller than any previously probed can produce characteristic effects at accelerators and solar neutrino experiments., Comment: 7 pages, harvmac, 2nd revision discusses recent indications of anisotropy of photons propagating over cosmological distances and is otherwise clarified. Report-no: HUTP-97/A008

Radioactive decays inside the Earth produce antineutrinos that may be detectable at the surface. Their flux and spectrum contain important geophysical information. New detectors need to be developed, discriminating between sources of antineutrinos, including the cosmic-background. The latter can be related to the frequency of supernovas.

My involvement with flavor physics began long before anyone knew about quarks, and my efforts were inspired by Julian Schwinger — my thesis advisor, mentor, critic, and dear friend for many years. This talk is dedicated to his memory.

We provide a detailed analysis of the problems and prospects of superstring theory c. 1986, anticipating much of the progress of the decades to follow., Comment: originally appeared as a Reference Frame in Physics Today, May 1986

We estimate the cross section for Higgs-boson production via bremsstrahlung from intermediate vector bosons produced in $\mathrm{pp}$ and $\overline{p}p$ collisions.

We estimate the cross section for Higgs-boson production in proton-proton collisions. We find that most of the cross section comes from a two-gluon annihilation process, in which the gluons couple to Higgs bosons via heavy-quark loops.

Could a particle accelerator destroy the world? Fears that the Relativistic Heavy Ion Collider at Brookhaven in the United States could trigger an unforeseen disaster have been allayed by two studies that show the risk of worldwide catastrophe to be truly negligible.

Principles of minimality and unifiability lead us to a unique family of mutants of the electroweak theory which are parametrized solely by the mass of a heavy {ital Z}{prime} boson. These models generate an additional vectorial current-current interaction at low energy, and modify the properties of the observed {ital Z} boson in a way that would appear (in the context of the standard model) as an apparently fractional number (exceeding three) of light neutrino species. Such alternative theories offer a foil against which to test our confidence in the orthodox theory.

Once upon a time, the life of the high-energy physicist was dominated by frequent astonishing and spectacular discoveries: new effects or new particles that were unexpected by the lumpen proletariat appeared with great regularity. Recall the spirit of the times a century ago: with the discoveries of the inert gases in 1894, X-rays in 1895, radioactivity in 1896, and the electron in 1897. Here are a dozen more contemporary examples

1987 has been truly a super year. We have seen the first nearby supernova in 383 years, not only in light but in antineutrinos, and more recently, in X-rays and gamma rays. The repercussions of this discovery are still coming: What is the mysterious companion of SN1987a seen in speckle photometry? What limits can we place on neutrino masses lifetimes, and interactions? How are axion theories constrained by the fact that the explosion took place more-or-less according to the theoretical script? Should we believe the curiously premature Mont Blanc observations? Since it was a blue giant that blew up, should we revise upwards our earlier color-blind estimates of supernova frequency? Will our community be fully prepared for the next supernova?

Once it was that particle theorists explained particles that were known to exist (like pion-nucleon resonances and strange particles) and predicted others that had to exist (like charmed particles, W’s and Z’s). Overwhelmed by the successes of their so-called standard model, they now find themselves enumerating the properties of particles that have no reason not to exist. Among these are countless candidates for the dark matter of galactic halos and the missing matter of the Universe, whose identification is surely a central problem at the frontier of cosmology and particle physics. With my colleagues Alvaro De Rujula and Uri Sarid, we introduce yet another, but seemingly outrageous dark matter candidate, but one that fulfils its task nonetheless: a stable and very massive electrically-charged particle.

Our discipline of elementary particle physics confronts the three great pincers of the Big Squeeze: we suffer from a lack of adequate funding, a theory that works too well, and a bit too much religious zeal.

We point out that the assumption of Lorentz noninvariance examined recently by Coleman and Glashow leads to neutrino flavor oscillations which are phenomenologically equivalent to those obtained by assuming the neutrinos violate the principle of equivalence. We then comment on the limits on Lorentz noninvariance which can be derived from solar, atmospheric, and accelerator neutrino experiments.

We examine certain extensions of the standard model in which $\mathrm{CP}$ violation is spontaneous and the strong $\mathrm{CP}$ problem is resolved. In these models, the $3\ifmmode\times\else\texttimes\fi{}3$ quark-mixing matrix is neither real nor unitary. However, to a precision of 0.1%, it is real and orthogonal. There are no readily observable $\mathrm{CP}$-violating effects other than those in the neutral kaon system.

Classical physics: The science of motion: mechanics Things that collide The behavior of gases Heat is a form of motion Atoms Tell me what electricity is, and I'll tell you everything else Let there be light Modern physics Quantum mechanics The world according to Einstein Inside the nucleus Elementary particle physics High-energy physics The methods of high-energy physics The universe and the particle.

Last month, 70 members of the U.S. Congress, including Henry Hyde, Chairman of the House Judiciary Committee, and J. C. Watts Jr. Republican Conference Chairman, signed a letter urging the federal government to ban all research on stem cells obtained from human embryos and fetuses. The letter calls upon the U.S. Department of Health and Human Services (DHHS) to reverse National Institutes of Health (NIH) Director Harold Varmus's decision to allow funding of pluripotent stem cell research. The lawmakers object “in the strongest possible terms” to Varmus's decision, as well as to the memorandum issued in January by DHHS General Counsel Harriet Rabb, which served as the legal basis for Varmus's position. In their letter, the members of Congress state, “Any NIH action to initiate funding of such research would violate both the letter and spirit of the federal law banning federal support for research in which human embryos are harmed or destroyed.” Federal laws and regulations, they claim, have protected human embryos and fetuses “from harmful experimentation at the hands of the Federal government” for more than two decades. “This area of law has provided a bulwark against government's misuse and exploitation of human beings in the name of medical progress. It would he a travesty for this Administration to attempt to unravel this accepted ethical standard.”

We constrain our previous double-{ital Z} model using available data. We show that it cannot lead to new physics in present or near-future experiments. We consider herein only {ital Z}{prime}-related phenomena, mainly low-energy induced interactions and modifications at the {ital Z} peak but also {ital p{bar p}} scattering measured by the Collider Detector at Fermilab and the forward-backward (or charge) lepton asymmetry in electron-positron annihilation.

Strong, electromagnetic, and weak forces are conjectured to arise from a single fundamental interaction based on the gauge group SU(5).

This paper reviews the success of the quark model in describing deep-inelastic lepton scattering. The neutral current predictions of a variety of unified gauge models are given and it is shown how experiment may distinguish among them. All the models involve new hadronic quantum numbers (charm or fancy). Their effects at high energy are explored.

A singlet majoron model is invoked to generate unstable neutrinos with masses comparable to present direct limits. The tau-neutrino is predicted to be short-lived, neutrino-counting experiments can yield non-integer results, unusual decay modes of W and Z are anticipated, and there can be no cosmic flux of muon-neutrinos.

We discuss the possibility that the upsilon particle is a Q Q bound state, where Q is a charge 1 3 , color sextet fermion. We explain why bound states of a Q with ordinary quarks and antiquarks might have escaped detection in accelerator searches for stable particles. We show that the Q and other bizarre fermions arise naturally in a unified theory in which the τ is a member of a weak SU(2) triplet.