An ab initio Calculation of the Universal Equation of State for the O(N) Model (2008)
O'Connor, Denjoe, Santiago, J. A., Stephens, C. R.
Using an Environmentally Friendly Renormalization Group we derive an ab initio universal scaling form for the equation of state for the O(N) model, y=f(x), that exhibits all required analyticity...
Perturbation Theory and the Renormalization Group in Genetic Dynamics (2008)
C. R. Stephens, A. Zamora, A. Wright
Abstract. Although much progress has been made in recent years in the theory of GAs and GP, there is still a conspicuous lack of tools with which to derive systematic, approximate solutions to their...
MERCADOS FINANCIEROS ADAPTIVOS (2007)
C. R. Stephens, H. Waelbroeck, D. Sudarsky, Federico Zertuche
Predecir la evolucion de mercados financieros es el sueno de mucha gente. Hoy en da existe un enorme rango de herramientas disponibles para ayudar llevar a cabo esta tarea, y que abarca desde lo mas...
Schemata as Building Blocks: Does Size Mattter? (2007)
C. R. Stephens, H. Waelbroeck, R. Aguirre
We analyze the schema theorem and the building block hypothesis using a recently derived, exact schemata evolution equation. We derive a new schema theorem based on the concept of effective fitness...
R. Poli, W. B. Langdon, M. Clerc, C. R. Stephens
Abstract. We propose a method to build discrete Markov chain models of continuous stochastic optimisers that can approximate them on arbitrary continuous problems to any precision. We discretise the...
An Analytic Equation of State for Ising-like Models (2006)
O'Connor, D. J., Santiago, J. A., Stephens, C. R.
Using an Environmentally Friendly Renormalization we derive, from an underlying field theory representation, a formal expression for the equation of state, $y=f(x)$, that exhibits all desired...
R. Poli, M. Clerc, W. B. Langdon, C. R. Stephens, Unam México
We propose a method to build discrete Markov chain models of continuous stochastic optimisers that can approximate them on arbitrary continuous problems to any precision. We discretise the objective...
The School of Medicine at the University of Southampton has undergone a process of consultation and staff development aimed at developing the leadership role of course coordinators. The paper reports...
Coarse Graining in an Evolutionary Algorithm with Recombination, Duplication and Inversion (2005)
A generalised form of recombination, wherein an offspring can be formed from any of the genetic material of the parents, is analysed in the context of a twolocus recombinative GA. A complete, exact...
Coarse graining in an evolutionary algorithm with recombination, duplication and inversion (2005)
A generalised form of recombination, wherein an offspring can be formed from any of the genetic material of the parents, is analysed in the context of a two-locus recombinative GA. A complete, exact...
Dimensional Reduction, Hard Thermal Loops and the Renormalization Group (2004)
Stephens, C. R., Weber, Axel, Hess, Peter O., Astorga, Francisco
We study the realization of dimensional reduction and the validity of the hard thermal loop expansion for lambda phi^4 theory at finite temperature, using an environmentally friendly...
Chryssomalakos , C., Stephens , C.R., Zamora , Adolfo
We show how the idea of coarse graining can be applied fruitfully to the area of genetic dynamics, both in the context of ¿effective¿ theories - leading to more appropriate effective degrees of...
Dimensional Crossover in the Non-Linear Sigma Model (2002)
O'Connor, Denjoe, Stephens, C. R., Santiago, J. A.
We consider dimensional crossover for an O(N) model on a d-dimensional layered geometry of thickness L, in the sigma-model limit, using ``environmentally friendly'' renormalization. We show how to...
Some Exact Results from a Coarse Grained Formulation of Genetic Dynamics (2001)
We extend a recently developed exact schema based, or coarse grained, formulation of genetic dynamics \cite{stewael,stewael1,stewael2} and its associated exact Schema theorem to an arbitrary...
Owen, D.K., Lewith, G., Stephens, C.R.
Patients are increasingly using complementary and alternative medicine, and doctors are responding to this in several ways, from being enthusiastic and interested to mystified and critical....
Owen, D.K., Lewith, G., Stephens, C.R.
Patients are increasingly using complementary and alternative medicine, 1 2 and doctors are responding to this in several ways, from being enthusiastic and interested to mystified and critical.3-5...
Bound States from Regge Trajectories in a Scalar Model (2000)
Weber, A., Vieyra, J. C. Lopez, Stephens, C. R., Dilcher, S., Hess, P. O.
The calculation of bound state properties using renormalization group techniques to compute the corresponding Regge trajectories is presented. In particular, we investigate the bound states in...
Schemata Evolution and Building Blocks (2000)
Stephens, C. R., Waelbroeck, H.
In the light of a recently derived evolution equation for genetic algorithms we consider the schema theorem and the building block hypothesis. We derive a schema theorem based on the concept of...
Schemata as Building Blocks: Does Size Matter? (2000)
Stephens, C. R., Waelbroeck, H., Aguirre, R.
We analyze the schema theorem and the building block hypothesis using a recently derived, exact schemata evolution equation. We derive a new schema theorem based on the concept of effective fitness...
Effective Fitness Landscapes for Evolutionary Systems (2000)
In evolution theory the concept of a fitness landscape has played an important role, evolution itself being portrayed as a hill-climbing process on a rugged landscape. In this article it is shown...
Effect of Mutation and Recombination on the Genotype-Phenotype Map (2000)
The effect of genetic operators other than selection, such as mutation and recombination, on the genotype-phenotype map is considered. In particular, when the genotypic fitness landscape exhibits a...
Schemata as Building Blocks: Does Size Matter? (2000)
C. R. Stephens, H. Waelbroeck, R. Aguirre
We analyze the schema theorem and the building block hypothesis using a recently derived, exact schemata evolution equation. We derive a new schema theorem based on the concept of e#ective fitness...
Glueball Spectrum from an Effective Hamiltonian (1998)
Hess, P. O., Weber, A., Stephens, C. R., H., S. A. Lerma, V., J. C. Lopez
Using simple and general arguments we propose an effective Hamiltonian for the description of low-energy pure QCD. The Hamiltonian is a function of spatially constant collective modes. Its...
Quantum Field Theory in the Limit x (1998)
Stephens, C. R., Weber, A., Vieyra, J. C. Lopez, Hess, P. O.
The asymptotic high momentum behaviour of quantum field theories with cubic interactions is investigated using renormalization group techniques in the asymmetric limit x
Universal Scaling Properties of Superconductors in Magnetic Fields (1997)
O'Connor, Denjoe, Stephens, C. R.
Based on renormalization group arguments we establish that for a superconductor in the presence of a weak external magnetic field, $B$, the dependence on $B$ and the deviation from the critical...
Regge Behaviour from an Environmentally Friendly Renormalization Group (1997)
Stephens, C. R., Vieyra, J. C. Lopez, Weber, A., Hess, P. O.
The asymptotic behaviour of cubic field theories is investigated in the Regge limit using the techniques of environmentally friendly renormalization, environmentally friendly in the present context...
Analysis of the Effective Degrees of Freedom in Genetic Algorithms (1996)
Stephens, C. R., Waelbroeck, H.
An evolution equation for a population of strings evolving under the genetic operators: selection, mutation and crossover is derived. The corresponding equation describing the evolution of schematas...
Boson Mapping in Field Theory (1996)
Hess, P. O., Vieyra, J. C. López, Stephens, C. R.
A boson mapping of pair field operators is presented. The mapping preserves all hermiticity properties and the Poisson bracket relations between fields and momenta. The most practical application of...
Why Two Renormalization Groups are Better than One (1996)
The advantages of using more than one renormalization group (RG) in problems with more than one important length scale are discussed. It is shown that: i) using different RG's can lead to...
Dimensional Crossover in the Large N Limit (1996)
O'Connor, Denjoe, Stephens, C. R., Bray, A. J.
We consider dimensional crossover for an $O(N)$ Landau-Ginzburg-Wilson model on a $d$-dimensional film geometry of thickness $L$ in the large $N$-limit. We calculate the full universal crossover...
Freire, F., O'Connor, Denjoe, Stephens, C. R., Van Eijck, M. A.
$\lambda\varphi^4$ theory at finite temperature suffers from infrared divergences near the temperature at which the symmetry is restored. These divergences are handled using renormalization group...
The Specific Heat of a Ferromagnetic Film. (1995)
Freire, F., O'Connor, Denjoe, Stephens, C. R.
We analyze the specific heat for the $O(N)$ vector model on a $d$-dimensional film geometry of thickness $L$ using ``environmentally friendly'' renormalization. We consider periodic, Dirichlet and...
Critical Temperature and Amplitude Ratios from a Finite-Temperature Renormalization Group (1994)
Van Eijck, M. A., O'Connor, Denjoe, Stephens, C. R.
We study $\l\f^4$ theory using an environmentally friendly finite-temperature renormalization group. We derive flow equations, using a fiducial temperature as flow parameter, develop them...
Environmentally Friendly Renormalization in Finite-Temperature Field Theory (1994)
Van Eijck, M. A., O'Connor, Denjoe, Stephens, C. R.
Contribution to the proceedings of the NATO workshop on the Electroweak Phase Transition and the Early Universe, Sintra, March 1994. To be published by Plenum Press.
Black hole evaporation without information loss (1994)
Hooft, G. 't, Stephens, C.R., Whiting, B.F.
An approach to black hole quantization is proposed wherein it is assumed that quantum coherence is preserved. A consequence of this is that the Penrose diagram describing gravitational collapse will...
Environmentally Friendly Renormalization (1993)
O'Connor, Denjoe, Stephens, C. R.
We analyze the renormalization of systems whose effective degrees of freedom are described in terms of fluctuations which are ``environment'' dependent. Relevant environmental parameters considered...
Heating Field Theory the ``Environmentally Friendly'' Way! (1993)
Van Ejick, M. A., O'Connor, Denjoe, Stephens, C. R.
We discuss how to implement an ``environmentally friendly'' renormalization in the context of finite temperature field theory. Environmentally friendly renormalization provides a method for...
O'Connor, Denjoe, Stephens, C. R.
Series for the Wilson functions of an ``environmentally friendly'' renormalization group are computed to two loops, for an $O(N)$ vector model, in terms of the ``floating coupling'', and resummed by...
Black Hole Evaporation without Information Loss (1993)
Stephens, C. R., Hooft, G. 't, Whiting, B. F.
An approach to black hole quantization is proposed wherein it is assumed that quantum coherence is preserved. A consequence of this is that the Penrose diagram describing gravitational collapse will...
Temperature Dependence of the QCD Coupling (1993)
Van Eijck, M. A., Stephens, C. R., Van Weert, Ch. G.
We present a one-loop calculation of a gauge invariant QCD beta function. Using both momentum and temperature renormalization group equations we investigate the running coupling in the magnetic...
Geometry the Renormalization Group and Gravity (1993)
O'Connor, Denjoe, Stephens, C. R.
We discuss the relationship between geometry, the renormalization group (RG) and gravity. We begin by reviewing our recent work on crossover problems in field theory. By crossover we mean the...