THEORETICAL PHYSICS. Daniel Bessis. M.S. Physics – Orsay University,
France, 1961. Ph.D. Physics – Sorbonne, Paris, France, 1965. Selected Papers.
THEORETICAL PHYSICS
Daniel Bessis M.S. Physics – Orsay University, France, 1961 Ph.D. Physics – Sorbonne, Paris, France, 1965 Selected Papers “Rapidly Converging Bounds for the Ground-State Energy of Hydrogenic Atoms in Superstrong Magnetic Fields”, C. R. Handy, D. Bessis, G. Sigismondi and T. D. Morley, Physical Review Letters 60, 253 (1988). “New method in the Combinatorics of the topological expansion”, D. Bessis, Communications in Mathematical Physics 69,147 (1979). “A Unitary Padé Approximant in Strong Coupling Field Theory and Application to the Calculation of the ρ and f0-Meson Regge trajectories”, D. Bessis and M. Pusterla, Il Nuovo Cimento 54, 243 (1968).
THEORETICAL PHYSICS Dr. Bessis is an international leader in the field of Padé Approximations and Orthogonal Polynomials. His main interest is the development and application of those methods to wide ranging areas of Physics and Engineering always keeping in mind both theoretical and computational aspects. Dr. Bessis started his scientific life as an aeronautical engineer, and spent three years in the French Army as a radar instructor. This gave him a strong experience in engineering problems. He then became a staff member at the Theoretical Division at the Center for Nuclear Studies of Saclay, France. While a visiting researcher at CERN (European Center for Nuclear Research) in Geneva, Switzerland, he started to develop a completely new summation method to deal with divergent series appearing in quantum field theory. This was the first use of the theory of Padé Approximations in this subject, and led to a revival of field theory over the bootstrap approach. For these accomplishments, he received the Prize of the French Physical Society for Theoretical Physics. Dr. Bessis also made a breakthrough in combinatorial topology by solving an important problem arising in quantum field theory involving the counting of graphs on surfaces of genus larger than zero. This problem remained unsolved for over than twenty-five years. The crucial step in the solution was the introduction of orthogonal polynomials with respect to exponential weights. Among the most relevant applications of this method are the computation of finite order corrections to the distribution of eigenvalues of random hermitean matrices, and the counting of topologically inequivalent ways to triangulate surfaces. This technique has been recently applied to two dimensional quantum gravity by Gross and Migdal (1990) among many others; see e.g. Physics Today April 1990. Fractal Geometry is an other of the many interest of Dr. Bessis: he discovered that the iterates of any polynomial form families of orthogonal polynomials. This allows one to transform a nonlinear problem (the composition of polynomials) into a linear one: the threeterm recursive relation fulfilled by orthogonal polynomials. As a result, the theory of Julia sets found many applications in statistical and quantum mechanics. Perhaps the most remarkable is the construction of an exactly solvable chaotic quantum model. This has been achieved by constructing a Schrodinger like operator whose spectrum is any given Julia set.detection of Gravitational waves and Diagnosis and Prognosis of mechanical systems. Presently Dr. Bessis has NSF and NASA subaward grants to use this method in the detection of Gravitational Waves produced by Black Holes or other asymmetrical celestial bodies. He has also a contract with the Navy to detect vibration bursts that can lead to Helicopter breakdown. He expects further contracts with oil companies to detect vibration bursts in drilling bits that could lead to destruction of the apparatus. Padé Approximations in Data Analysis lead to an entirely new approach in which the wanted burst signal is identified by the perturbation it produces in the surrounding background stationary signals: this approach appears to be far more sensitive that standard methods such as Fast Fourier Transform or Wavelets. Dr. Bessis has published 120 papers in peer reviewed professional journal and his work has been cited more than 1432 times.
