Professor of Physics

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

(949) 824-5596

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.

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 later his undergraduate physics degree, in theoretical physics, from the University of Milano, Italy. As a Fulbright Fellow he got 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. He then joined the Physics Department of the University of California at Irvine as a junior faculty member 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. In 2006-2007 and 2012-2013 he has held a visiting appointment at the Albert Einstein Institute (AEI) in Berlin, Germany. In 2009 he was a vistor at the Institut des Hautes Itudes Scientifiques (IHES) in Bur-sur-Yvette, France.

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.

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.

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 weak field perturbation theory, have difficulties in dealing with highly nonlinear fluctuations Discretized models for quantum gravity introduce a fine space-time mesh, and attempt to solve the fundamental equations exactly on some of the world's fastest massivley paralle supercomputers. 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.

Single graviton exchange between two massive sources.

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.

* (For a more complete list see
Research Gate,
Google Scholar or
Spires).*

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

*
Inconsistencie from a Running Cosmological Constant
(with R. Toriumi), (paper),
published in the International Journal of Modern Physics (paper).*

*
Wheeler-DeWitt Equation in 3+1 Dimensions
(with R. Toriumi and R.M. Williams), (paper),
published in Physical Review D (paper).*

*
Composite Leptons at the LHC
(with R. Toriumi), (paper).*

*
Wheeler-DeWitt Equation in 2+1 Dimensions
(with R.M. Williams), (paper),
published in Physical Review D (paper).*

*
Discrete Wheeler-DeWitt Equation
(with R.M. Williams), (paper),
published in Physical Review D (paper).*

*
Scale-Dependent Newton's G in the Conformal Newtonian Gauge
(with R. Toriumi), (paper),
published in Physical Review D (paper).*

*
Cosmological Density Perturbations with a Scale-Dependent Newton's G
(with R. Toriumi), (paper),
published in Physical Review D (paper).*

*
Ultraviolet Divergences and Scale-Dependent Gravitational Couplings
(January 2010, 24 pp.), Pleanary Talk,
12-th Marcel Grossmann Conference
on Recent Developments in General Relativity, Astrophysics and Relativistic Field Theories,
UNESCO, Paris, July 12-18, 2009
(proceedings contribution).*

*
Gravitational Wilson Loop in Discrete Gravity
(with R.M. Williams), (paper),
published in Physical Review D (paper).*

*
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).*

*
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).*

*
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).*

*
Laurea Thesis on "Dynamical Symmetry Breaking in Gauge Theories" (1976, 144pp.),
my doctoral thesis at the University of Milano.
The subject was dynamical
symmetry breaking in the Standard (GSW) Model of Electro-Weak Interactions,
along the lines of the BCS superconductor theory.
There the relevant Goldstone bosons are made up of electron-hole pairs, and therefore
are not elementary excitations (unlike phonons).
In the Quantum Field Theory models I discussed in my thesis the Higgs boson is also a fermion-antifermion
composite, and therefore not a fundamental elementary scalar as is the case for the original Higgs model.
In some ways this was a technicolor theory, four years before the term
technicolor was first introduced.
(thesis as pdf).*

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