## Herbert W. Hamber

Professor, Physics & Astronomy

School of Physical Sciences

School of Physical Sciences

PH.D., University of California, Santa Barbara, 1980

OTH, University of Milan

OTH, University of Milan

University of California, Irvine

3172 Frederick Reines Hall

Mail Code: 4575

Irvine, CA 92697

3172 Frederick Reines Hall

Mail Code: 4575

Irvine, CA 92697

**Research Interests**

Quantum Field Theory, Theoretical Particle Physics, Statistical Mechanics, General Relativity, Computation

**Academic Distinctions**

**Appointments**

**Research Abstract**

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.

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 at NCSA 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. These large scale calculations are performed under the NSF-sponsored Supercomputer MetaCenter program.

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

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 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 at NCSA 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. These large scale calculations are performed under the NSF-sponsored Supercomputer MetaCenter program.

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

**Publications**

On the Gravitational Scaling Dimensions, preprint UCI-99-20, published in the Physical Review D61 (2000) 124008.

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

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

Feynman Rules for Simplicial Gravity (with S. Liu), Preprint UCI-96-6, published in Nuclear Physics B472 (1996) 447-477.

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

**Professional Societies**

Member, Institute for Advanced Study
Princeton, NJ

Member, New York Academy of Sciences

**Last updated**

03/12/2002