The HERBERT HAMBER Home Page

UC IRVINE DEPARTMENT OF PHYSICS





Herbert W. Hamber

Professor of Physics

Theoretical Particle Physics, Statistical Mechanics, Quantized Gravitation, Mathematical Physics

(949) 824-5596

hhamber@uci.edu

For futher personal information, see professor's Hamber address.

More details on the book "QUANTUM GRAVITATION" published by Springer in 2008 can be found here.

For recent memberships see here.

(For CERN address, please lookup entry in the CERN phone book).

Link to Aeneas Supercomputer Project.

Link to Mathematica Course.

Graduate Ph.D. students recently supervised: Shao Liu (thesis), Geoff Kagel (thesis) Reiko Toriumi (thesis) .

Professor Hamber earned his high school Abitur from the Deutsche Schule Mailand, and his undergraduate physics degree, in theoretical physics, from the University of Milano, Italy. As a Fulbright Fellow he obtained his Ph.D. from the University of California at Santa Barbara in 1980. After a postdoctoral appointment in the theory division of DoE's Brookhaven National Laboratory , he became a member of the Institute for Advanced Study in Princeton NJ, before joining the Physics Department of the University of California at Irvine in 1985. During the academic year 1993-1994 he has held a visiting appointment at the European Laboratory for Particle Physics (CERN) in Geneva, Switzerland. During the academic year 2006-2007 he has held a visiting appointment at the Albert Einstein Institute (AEI) in Berlin, Germany.

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Present fields of interest range from elementary particle theory to statistical mechanics, gravitation and advanced scientific computation. Interactions between quarks and gluons are described by Quantum Chromodynamics, which is believed to be the fundamental theory of the strong interactions, and is ultimately responsible for nuclear binding. Contrary to electromagnetic interactions, the force between quarks does not decrease with distance, and gives rise to the confinement phenomenon. The method known as lattice gauge theory has allowed one to compute from first principles some of the properties of quarks and gluons. Instead of operating in a space-time continuum, the quantum field equations of QCD are solved on a four-dimensional space-time lattice. In a number of instances the equations are so complex that the world's fastest supercomputers are needed to solve them. Professor Hamber and his students are involved in a number of collaborative projects with researchers in the US and in Europe which attempt to extract detailed predictions for strong interaction parameters. One such initiative, the US QCD Teraflop Project, involves 22 institutions and proposes to build the world's fastest massively parallel supercomputer.

In the Feynman path integral approach to quantum mechanics, the propagation of particles is described by a random walk in space. In considering the quantum mechanics of string-like objects, one is led to study the properties of random surfaces describing the motion of the string through space and time. Current interest in strings arises from the fact that supersymmetric string theories have been proposed as a unified model for all elementary particle interactions. The statistical mechanics analog of this problem is a fluctuating random surface embedded in some higher dimensional Euclidean space. Recent work has addressed the issue of what the geometry of random surfaces is, and what can be learned from it about the quantum mechanical properties of strings.

hwh 2-d Simplicial Complex

A third line of inquiry concerns the problem of finding a consistent scheme for quantizing the gravitational field. In a quantum-mechanical theory of gravitation the geometry of space and time is subject to strong fluctuations at extremely short distances. Instead of parameters, physical distances and times become quantum operators. Traditional methods, based on perturbation theory, have difficulties in dealing with highly nonlinear fluctuations (click here to see some lowest order Feynman diagrams relevant to the potential). Discretized models for quantum gravity introduce a fine space-time mesh, and attempt to solve the fundamental equations exactly on some of the fastest supercomputers, such as the massively parallel 512-node CM5 supercomputer at the National Center for Supercomputer Applications (NCSA) in Urbana, Ill., or the 512-node IBM SP2 supercomputer at the Cornell University Theory Center in Ithaca, NY. The hope is that eventually a solution to the quantum equations will provide new insights and answers to some basic particle physics and cosmological questions. These large scale calculations are performed under the NSF-sponsored Supercomputer MetaCenter program.

hwh Graviton Exchange

In addition to his research, Professor Hamber has taught over the last few years graduate courses in elementary particle theory, quantum mechanics, quantum field theory, general relativity, statistical mechanics and computational physics.

Representative Publications:

(See also the list under index).

Quantum Gravitation - The Feynman Path Integral Approach (Springer Publishing, Berlin & New York, 2009, 342 pp.), [link to book page].

Gravitational Wilson Loop in Discrete Gravity (with R.M. Williams), (paper), submitted to the Physical Review D .

Quantum Gravity on the Lattice (December 2008, 63 pp.), in "Quantum Gravity: Challenges and Perspectives" , Bad Honnef, April 2008, edited by Hermann Nicolai, General Relativity and Gravitation journal special issue (paper); published version here.

Gravitational Wilson Loop and Large Scale Curvature (with R.M. Williams, AEI preprint May 2007), (paper), published in the Physical Review D (paper).

Lattice Quantum Gravity (April 2008), lecture at "Quantum Gravity: Challenges and Perspectives" , Bad Honnef, April 2008(slides converted to pdf).

Renormalization Group Running of G: The Static Isotropic Case (with R.M. Williams, July 2006), (paper), published in the Physical Review D (paper).

Discrete and Continuum Quantum Gravity (AEI preprint, April 2007, 224 pp.), (paper).

Constraints on Gravitational Scaling Dimensions from Non-Local Field Equations (with R.M. Williams, July 2006), (paper), published in Physics Letters B (paper).

Quantum Gravity in Large Dimensions (with R.M. Williams, November 2005), (paper), published in the Physical Review D (paper).

Nonlocal Effective Gravitational Field Equations and the Running of Newton's G (with R.M. Williams, June 2005), (paper), published in the Physical Review D (2005) (paper).

Non-Perturbative Gravity and the Spin of the Lattice Graviton (with R.M. Williams), DAMTP/UCI preprint June 2004,(paper), published in the Physical Review D70, 124007-1-24 (2004),(published version in pdf).

Non-Local Effective Field Equations for Quantum Cosmology (with R.M. Williams, November 2005), (paper), published in Modern Physics Letters A (paper).

Exact Bianchi Identity in Regge Gravity, (with G. Kagel), Irvine preprint May 2004, (paper), published in Classical and Quantum Gravity 21, 5915-5947 (2004), (published version in pdf).

Scaling Dimensions of Quantized Gravity, published in the Proceedings of the 9th Marcel Grossmann Meeting on "Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories" (MG 9), Rome, Italy, 2-9 Jul 2000 (published version in pdf).

On the Gravitational Scaling Dimensions, published in the Physical Review D61 (2000) 124008 (published version in pdf).

Measure in Simplicial Gravity (with R.M. Williams), Preprint DAMTP-97-75, published in the Physical Review D59 (1999) 064014 (published version in pdf).

AENEAS - A Custom-built Parallel Supercomputer for Quantum Gravity, Preprint UCI-98-31 (gr-qc/9809090), (paper).

Gauge Invariance in Simplicial Gravity (with R.M. Williams), Preprint CERN-TH./96, published in Nuclear Physics B487 (1997) 345-408 (published version in pdf).

On the Quantum Correction to the Newtonian Potential (with S. Liu), published in Physics Letters B357, 51-56 (1995) (paper).

Feynman Rules for Simplicial Gravity (with S. Liu), published in Nuclear Physics B472 (1996) 447-477 (paper).

Newtonian Potential in Quantum Regge Gravity (with R.M. Williams), Preprint CERN-TH.7314/94, published in Nuclear Physics B435 (1995) 361-398 (publisghed version in pdf).

Discrete Gravity in One Dimension (with R.M. Williams), Preprint CERN-TH.7378/94, published in Nuclear Physics B451 (1995) 305-324. (paper).

Dynamically Triangulated Ising Spins in Flat Space (with M. Vekic and S. Liu), published in Physics Letters B329, 444-449 (1994) (paper).

Diffeomorphism Invariant Correlations in Quantized Gravity, published in the Physical Review D50 (1994) 3932-3941 (paper).

Random Ising Spins in Two Dimensions - A Flat Space Realization of the KPZ Exponents (with M. Vekic and S. Liu), Preprint CERN-TH.7355, published in the Physical Review D51 (1995) 4287-4294 (paper).

Simplicial Gravity Coupled to Scalar Matter (with R.M. Williams), published in Nuclear Physics B415 (1994) 463-505 (paper).

Simplicial Quantum Gravity in Three Dimensions: Analytical and Numerical Results (with R.M. Williams), published in the Physical Review D47, 510-532 (1993), (published version in pdf).

Scalar Fields Coupled to Four-Dimensional Lattice Gravity,, published in the Proceedings of International Europhysics Conference on High Energy Physics, Marseille, France, July 22-28, 1993 (Editions Frontieres, Gif-sur-Yvette, 1994) 211-213 (paper) .

Phases of Simplicial Quantum Gravity in Four Dimensions: Estimates for the Critical Exponents, published in Nuclear Physics B400, 347-389 (1993) (paper).

Phases of Simplicial Quantum Gravity, in "Random Surfaces and Two-Dimensional Gravity", published in Nuclear Physics B 25A, 150-175 (1992) (paper or published version in pdf).

Lattice Quantum Chromodynamics with Dynamical Fermions, published in "Probabilistic Methods in Quantum Field Theory and Quantum Gravity", Cargese Summer School 1989, (Plenum Press, New York 1990), 167-182, published version in pdf).

Physics Goals of the QCD Teraflop Project (with N. Christ et. al.), published in the International Journal of Modern Physics C 2, 829-947 (1991) (paper).

Fluctuations and Correlations in Simplicial Quantum Gravity, published in Nuclear Physics B26 (Proceedings Supplement) (1992) 581-583 (paper or scanned copy).

Phases of Four-Dimensional Simplicial Gravity, published in the Physical Review D45 (1992) 507-512, (published version in pdf).

Properties of Hadrons in Lattice Quantum Chromodynamics with Dynamical Wilson Fermions, published in the Physical Review D39, 896-908, (1989) (published version in pdf).

Critical Properties of Two-Dimensional Simplicial Quantum Gravity (with M. Gross), published in Nuclear Physics B364, 703-733, (1991) (paper,or scanned copy).

Random Ising Spins in Two Dimensions: A Flat Space Realization of the Knizhnik-Polyakov-Zamolodchikov Exponents (with M. Vekic and S. Liu), published in the Physical Review D51, 4287 (1995), (published version in pdf).

Critical Behavior in Simplicial Quantum Gravity in Four Dimensions , Nucl. Phys. B Proc. Supp. 20 (1991) 728 (paper) .

QCD on the Lattice and Hadron Spectroscopy , in "Nonperturbative Methods in Field Theory", published in Nuclear Physics B1A (Proc. Suppl.) (1987) 133-174. (paper) .

Non-Trivial Fixed Point for Quantum Gravity in Four Dimensions, Preprint November 1990 (paper) .

Simplicial Quantum Gravity, lecture notes published in "Gauge Theories, Critical Phenomena and Random Systems", Proceedings of the 1984 Les Houches Summer School, Session XLIII, (edited by K. Osterwalder and R. Stora, North Holland, 1986), (paper and figures).

Simplicial Quantum Gravity from Two to Four Dimensions, Lectures given at the 1989 Cargese NATO workshop on "Probabilistic Methods in Quantum Field Theory and Quantum Gravity", published in the proceedings (Plenum Press, New York 1990), 243-257 (paper or published version in pdf).

Two-Dimensional Simplicial Quantum Gravity, (with R.M. Williams), published in Nuclear Physics B267 (1986) 482-496 (paper) .

Simplicial Quantum Gravity with Higher-Derivative Terms: Formalism and Numerical Results in Four Dimensions, (with R.M. Williams), published in Nuclear Physics B269 (1986) 712-743 ((paper).

Higher Derivative Quantum Gravity on a Simplicial Lattice, (with R.M. Williams), published in Nuclear Physics B248 (1984) 392-414 and B260 (1985) 747 ((paper).

Chiral Condensates and Wilson Fermions, (with F. David), published in Nuclear Physics B248 (1984) 381, (published version in pdf).

Glueball Mass Estimates in Lattice QCD (with U. Heller), published in the Physical Review D29 (1984) 928, published version in pdf).

Lattice Gauge Theories at Large n_f, published in Physics Letters 126B (1983) 471, published version in pdf).

The Axial Vector Current Anomaly and the Meson Decay Constants for the Improved Lattice Fermion Action, (with C.M. Wu), published in Physics Letters 136B (1984) 255, published version in pdf).

Some Predictions for an Improved Fermion Action on the Lattice, (with C.M. Wu), published in Physics Letters 133B (1983) 351, published version in pdf).

Mesons Containing a Heavy and a Light Quark in Lattice QCD, published in the Physical Review D27 (1983) 2239.

Numerical Estimates for the Spectrum of Quantum Chromodynamics, (with G.Parisi), published in the Physical Review D27 (1983) 208.

Considerations on the Numerical Analysis of QCD, (with E. Marinari, G. Parisi and C. Rebbi), published in Nuclear Physics B225 [FS9] (1983) 475, published version in pdf).

Chiral Symmetry Breaking and Light Quark Masses in Lattice QCD, published in the Physical Review D31 (1985) 586, (published version in pdf).

Complex Probabilities and the Langevin Equation, (with H.C. Ren), published in Physics Letters 158B (1985) 330, published version in pdf).

Numerical Estimates of Hadron Masses in a Pure SU(3) Gauge Theory, (with G. Parisi), published in Physical Review Letters 47 (1981) 1795, (published version in pdf).

Renormalization-group Calculations for U(1) Symmetric Spin Systems and Gauge Theories", published in the Physical Review D24 (1981) 942, (published version in pdf).

The O(n) Heisenberg Model Close to n=d=2, (with J. Cardy), published in Physical Review Letters 45 (1980) 499, (published version in pdf).

Herbert W. Hamber

hhamber@uci.edu)

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