## Theoretical Condensed Matter Physics

### Allan Widom

Professor

PhD Cornell University, 1968

(617)373-2928

widom@neu.edu

### Research Summary:

The main area of research involves applications of quantum field theory at the interface between high energy theory and condensed matter theory. The work is almost always done in very close collaboration with experimentalists both at Northeastern University and in Europe. The research topics are extremely varied, and only some of the topics are briefly listed below.

(i) Quantum electrodynamics has been applied to electrical engineering circuits in low temperature (and more recently high temperature superconducting Josephson weak link circuits). Macroscopic quantum states have been predicted and observed in such circuits allowing for studies on the nature of the quantum mechanical measurements and the nature of the thermodynamic second law entropy increase and its connection with what we perceive as the forward direction in time. The Feynman-Einstein-Tolman-Podolsky notions of forward and backward propagation of signals in quantum field theory is taken quite seriously. Although usually restricted to high energy particle physics, such time propagation may be applied to electrical engineering circuits.

(ii) Macroscopic quantum mechanics and the nature of time reversal symmetry has long appeared important for processes involving K mesons. In particular, at the F factory (to built in Rome) there will be there will be copious production of particle-antiparticle pairs of K Mesons. Quantum interference in detection of the K decay products will be measured on the macroscopic length scale of centimeters. This gives us the opportunity to investigate the Einstein-Tolman-Podolsky notion that ‘future measurements’ can have an effect on ‘past measurements’. Similar oscillations studies are being carried out for neutrinos and other Fermions.

(iii) Presently there is no experimental evidence for or against quantum gravity (i.e. quantum general relativity), although the experimental evidence for or against quantum gravity (i.e. quantum general relativity), although the experimental evidence for classical general relativity is quite substantial. The quantum gravity predictions suffer from being too large (divergent) in theory, and from being too small for experimental observation. Just as macroscopic quantum electrodynamics presents an electrical engineering problem, macroscopic quantum gravity presents a mechanical engineering problem. One must find quantum ‘stress-curvature-strain’ relations (the two sides of the Einstein field equations). There is a long way to go in this effort.

### Recent Publications:

S. Sivasubramanian, Y.N. Srivastava, G. Vitiello and A. Widom, “Quantum dissipation induced noncommutative geometry” accepted for publication in *Physics Letters A*.

S. Sivasubramanian, Y.N. Srivastava, and A. Widom, “Landau-Khalatnikov Circuit model for Ferroelectric Hysteresis”, accepted for publication in *IEEE (UFFC)*.

S. Sivasubramanian, Y.N. Srivastava, and A Widom, “Microscopic Basis of Thermal Supperradiance”, *Journal of Physics: Condensed Matter* 15, 1109 2003.

Y. N. Srivastava and A. Widom, “Hadronic Equipartition Of Quark And Glue Momenta”, *Phys. Rev. D *63, 077502 (2001).

Y.Srivastava, A. Widom, S. Pacetti, and G.Pancheri, “Dispersive Techniques for alpha_s and R-had and the Instability of the QCD Vacuum,” eConf CO10430:T19, (2001).