Sidney Bludman

Professor of Physics Emeritus
  • Assistant Professor, Lehigh University (1950-52)
  • Staff Physicist, Lawrence Berkeley Laboratory and Lecturer, University of California (1952-61)
  • Visiting Fellow, Institute for Advanced Study (1956-57)
  • Professor of Physics & Astronomy, University of Pennsylvania (1961-99)
  • Visiting Professor, Imperial College (1967-68)
  • Visiting Professor, Tel-Aviv University (1971-72)
  • Lady Davis Professor, Hebrew University (1976-77)
  • Visitor, Institute for Theoretical Physics, University of California, Santa Barbara (1985, 1997)
  • Visitor, Center for Particle Astrophysics, Berkeley (1990-93)
  • Guggenheim Fellow (1983-84)
  • Scientific Director, Les Houches Summer Institute on Supernovae (1990)
  • Summer visitor, Institute for Particle and Nuclear Astrophysics, Lawrence Berkeley Laboratory (1994-95)
  • Summer visitor, Institute for Nuclear Theory, University of Washington (1996)
  • Visiting Professor, DESY Theory Group, Hamburg (1999-2006)
  • Visiting Professor, Universidad de Chile, Santiago (2006-2012)
  • Visiting Professor, University of Maryland (2012- )

Born to impoverished Polish immigrants, Bludman was lucky enough to attend the Bronx High School of Science (1940-1943) and the American Institute of Science Laboratory (1942). After a few months at City College of New York (1943), he transferred to Cornell University (1943-45, A.B. 1945). After a year (1945-46) in the U.S. Navy, he studied under Gregory Breit at Yale University (1946-50, M.S. 1948, Ph.D. 1951). He then became Assistant Professor at Lehigh University (1950-52), before being appointed to the Lawrence Berkeley Laboratory staff (1952-61). In 1949, he married Doris Marian Wittenberg (1926-69), who bore him three sons: Peter (b1953), Joel (b1955), Lee (b1957). After her death, he married Ellen Gore Schaffer (1949-) in 1988.

Research Interests: 

Nuclear Physics

Bludman’s Ph. D thesis was on the Born-Oppenheimer approximation (1954c). After graduation, he worked on underwater sound propagation (1951) for one summer at the Woods Hole Oceanographic Institution. At the Lawrence Berkeley Laboratory (1952-61), he began working on high energy physics (1954a, 1954d, 1955a,1960a, 1980b), helping to design an important magnetic spectrometer (1957a).

Neutrino Physics and the Weak Interactions

At the Lawrence Berkeley Laboratory, Bludman soon specialized in the weak interactions (1956a-c, 1958a, 1959a, 1959, 1960a, 1961, 1964a, 1965, 1967a,b) . He early proposed that the electron and muon neutrinos were distinct (1959a, 1963b,c).

Field Theory and Statistical Physics

Bludman’s early interest in classical field theory (1954b) quickly morphed into covariant field theory (1957b, 1963a,b, 1966d-e, 1967b), into general relativity(1960d,e) and into the properties of ultradense matter (1968,1970a, 1972, 1976b,c, 1980b). He and Kenneth Watson wrote the basic papers (1960b,c) on relativistic beams penetrating cold plasma (1960b, 1960c), important in accelerators and in ABM defense. Together with Dallas C. Kennedy, he studied non-equilibrium thermodynamics of radiation and matter (2004b).

Gauge Symmetries and Spontaneous Symmetry Breaking at the University of Pennsylvania

Bludman’s lifelong obsession with symmetry (1958b, 1966b, 1979f)) ultimately led him to the first gauge theory of the weak interactions and the prediction of weak neutral currents (1958b, 1966b, 1979f, 1992c, 1993a). When he came to the University of Pennsylvania, Abraham Klein led him into broken symmetry by by their discovery that the Goldstone theorem’s failed in theories with long range interactions (1963d, 1963e, 1966c).

Neutrinos at the Particle Physics-Astrophysics Interface

High energy astrophysics/cosmology deals with the testing and application of nuclear and elementary particle physics under extreme conditions obtaining only in compact objects or in the very early Universe. Bludman has studied the birth, evolution, and death of stars and of the Universe (1974c). He studied constraints on neutrino masses and lifetimes (1974a, 1991d-e, 1992a) and, together with Haeshim Lee, Tom Gaisser, Todor Stanev, atmospheric neutrinos (1983a-e, 1984b, 1985a, 1986a,b) .

Stellar Collapse and Supernovae IIa

Bludman’s interest in stellar structure (1973a,b) was first inspired by Hans Bethe at the Aspen Institute for Physics. At the end of nuclear burning, massive stars suddenly implode, emitting 10-15% of their rest mass in neutrinos, ejected matter, and light. Bludman studied neutrino radiation transport out of dense stellar cores (1973d, 1974b, 1975a, 1975b, 1975c, 1975d, 1976d,e, 1977b,c, 1978ab, 1979c,e, 1986c, 1993c, 1994b, 1995a, 1999d). He and N. Sack, I. Lichtensdadt (1980a,c) showed that a spherical explosion could not be driven by prompt neutrino emission. Bludman and P. Schinder developed general relativistic hydrodynamics (1987a, 1988a,e, 1989a) and the implications of observing the nearby supernova 1987A (1987b-d, 1988b,c, 1989b). Bludman directed the 1990 supernova session of the Les Houches Summer Institute and edited its proceedings (1990c, 1991a).

Solar Neutrinos and Stellar Structure

The deficiency in type nu-e neutrinos (1973c, 1990b, 1991b, 1992b,d, 1993b) led Bludman and D.C. Kennedy to study models for solar structure (1996a) and classical scaling symmetry (2010a-c, 2011a,b, 2012a). They obtained a simple analytic fit to the mechanical and thermal structure of the present Sun, to adequately describe and interpret the energy and neutrino production in standard and non-standard solar models (1999a). They found a variational formulation (1998b) for the four equations of mechanical and thermal equilibrium, identifying variational scaling symmetries with non-conservation laws. (In mechanics, the resulting nonconservation law is the Law of Clausius, leading to the Virial Theorem). In the hydrostatics of self-gravitating spheres, the nonconservation law leads directly to well-known properties of polytropes and of chemically homogeneous stellar cores.

Recently Accelerating Universe

Bludman’s early interests in cosmology (1983f, 1974a,c, 1977a, 1979a,f, 1981a,b, 1984a, 1989c, 1995b, 1996b,1997a, 1998a) were revived by the surprising observations that the homogeneous cosmological expansion recently started accelerating because of a small vacuum energy (1999c,e). Even if dynamic, observational differences between an additional negative-pressure material component within general relativity (Dark Energy) and low-curvature modifications of general relativity (Dark Gravity) are extremely small (2000b,2001a-c, 2003a,b, 2004a,b, 2006, 2007, 2008a,b, 2009. The standard cosmological model is now the flat LCDM model, consisting of cold dark matter and a small cosmological constant, a constant of nature. The constants of nature observed in our universe may be a consequence of extending anthropic reasoning to a multiverse of theoretically possible universes.

Popular Lectures and Book Review

Bludman won a 1956 Gravity Research Foundation award for an essay On the Existence of Gravitational Insulators. He addressed the 2004 IAU tercentenary meeting on Kepler’s Supernova. Bludman always involved himself in the rights of scientists, particularly dissidents and refuseniks in the Soviet Union. In 1984, when the University of Pennsylvania awarded Andrei Sakharov an honorary degree, Bludman made the baccalaureate response The Blessing and the Curse of Science. He reviewed the following books:

  • T.C. Schelling and M.H. Halperin, Strategy and Arms Control (Twentieth Century Fund, 1961) (1961b) 
  • Recent Developments in Gravitation. Cargese, 1978 (ed. M. Levy and S. Deser, Plenum Press, 1979), Science 208, 589 (1980) (1980d)  
  • General Relativity and Gravitation (ed. A. Held, Plenum Press, 1980), Science 209, 1234 (1980) (1980e)) Physics Today 47, 63 (1994). 
  • To Fulfill a Vision (ed. Y. Ne’eman, Addison-Wesley, 1981), Science 217, 528 (1982) (1982e) 
  • R.E. Marshak, Conceptual Foundations of Modern Particle Physics (World Scientific, 1993), Physics Today 47, 63 (1994).

Selected Publications: 


  • Is Cosmological Acceleration Driven by Classical Space-Time Geometry?, Intl. J. Mod. Physics D 17, 1-28, (2008). [Get article]
  • Gravitational Vacuum Energy in our Recently Accelerating Universe, J. Physics Conf. Ser. 161, 012026(2009). [Get article]
  • Invariant Relationships Deriving From Classical Scaling Transformations, with Dallas Kennedy (2010). [Get article]
  • Scale Invariant Stellar Structure, with Dallas Kennedy (2010). [Get article]
  • Kepler's 1604 Supernova and Star of Bethlehem [Get article]
  • Measuring Dark Energy Parameters to Select Theoretical Models [Get article]