Selected Academic Publications

Selected Academic Publications Public Domain Only C. Baxter Journal Papers Conference Papers Preprints Graduate Degree Theses Technical Reports

Radiation Pressure and Momentum Transfer in Dielectrics: The Photon Drag Effect, Rodney Loudon, Stephen M. Barnett and C. Baxter, Physical Review A, 71, 063802 (2005).

Coherence Length for a Trapped Bose Gas, Stephen M. Barnett, Sonja Franke-Arnold, Aidan S. Arnold and Colin Baxter, Journal of Physics B, 33, 4177 (2000).

Topological Equivalence in the Theory of a Trapped Cold Ion, C. Baxter and R. Loudon, Journal of Modern Optics, 45, 1303 (1998).

Radiation Pressure and Coherent States of Two-Level Atoms, C. Baxter, Physical Review A, 51, 3378 (1995).

Cold Rydberg Atoms as Realizable Analogs of Chern-Simons Theory C. Baxter, Physical Review Letters, 74, 514 (1995).

Center-of-Mass Motion of an N-particle Atom or Ion and the Thomas-Reiche-Kuhn Sum Rule C. Baxter, Physical Review A, 50, 875 (1994).

Counterrotating Terms and the Rotating Wave Approximation in Minimally Coupled Multilevel Systems C. Baxter, Annals of Physic, 234, 404 (1994).

Theory of Radiation Forces and Momenta for Mobile Atoms in Light Fields V. E. Lembessis, M. Babiker, C. Baxter and R. Loudon, Physical Review A, 48, 1594 (1993).

Canonical Approach to Photon Pressure C. Baxter, M. Babiker and R. Loudon, Physical Review A, 47, 1278 (1993).

The Thomas-Reiche-Kuhn Sum Rule for an Atom of N Equally-Spaced Energy Levels C. Baxter, Journal of Physics B, 25, L589 (1992).

Jaynes-Cummings Hamiltonian in a Covariant Gauge C. Baxter, Physical Review A, 44, 3179 (1991).

Alpha-Lorentz Gauge QED C. Baxter, Annals of Physics, 206, 221 (1991).

Gauge Invariant QED with Arbitary Mixing of p.A and q.E Interactions C. Baxter, M. Babiker, R.Loudon, Journal of Modern Optics, 37, 685 (1990).

A Hybrid Gauge Transformation for a Coupled Hydrogen Atom-Field System Colin Baxter, Journal of Physics A, 22, 3717 (1989).

Electromagnetic Tensors and the Photon Drag Effect S. M. Barnett, C. Baxter and R. Loudon, Physics 2005, A Century after Einstein, Warwick, UK. April 10 - April 14, 2005.

Photon Drag and Radiation Momentum C. Baxter, S. M. Barnett and R. Loudon, ICAP 2002, XVII International Conference on Atomic Physics, Cambridge, Massachusetts, USA. July 28 - August 2, 2002.

Quantum Mechanics of Two-Dimensional Motion C. Baxter, R. Loudon, CLEO/Europe-EQEC98, Glasgow, Scotland. September 14-18, 1998. Technical Digest, EQEC98: Library of Congress Call No. QC685.E97 1998; ISBN: .

Topological Features of a Trapped Cold Ion C. Baxter, R. Loudon, NQEC15, National Quantum Electronics Conference, Cardiff, Wales. September 8-11, 1997. Technical Digest, QE13.

Quantum Electrodynamics of Radiation Pressure C. Baxter, M. Babiker and R. Loudon, Quantum Electronics and Laser Science Conference, Baltimore, Maryland, USA, May 2-7, 1993. OSA Technical Digest, Series 3, 283.

Gauge Invariant QED C. Baxter, M. Babiker and R. Loudon, National Quantum Electronics Conference, Oxford, England, September 18-22 1989. Technical Digest, QE9.

Topological Eigenfunctions in Two-Dimensions C. Baxter, R. Loudon. Preprint #1.

Radiation Pressure and Photon Drag C. Baxter, Stephen M. Barnett, R. Loudon. Preprint #2.

Radiation Interaction with Non-Relativistic Bound Charges C. Baxter, M.Sc. Thesis, University of Essex, 1988.

Gauge Transformations in Non-Relative Quantum Electrodynamics C. Baxter, Ph.D. Thesis, University of Essex, 1991.

Radiation from Cellphone Transmitter Towers Colin Baxter, Colin-Baxter.com, August 2003 (updated March 2004).

Pinpointing Molecules with a Laser C. Baxter, Achievements in Chemistry, 4. UK Science and Engineering Research Council, Swindon, 1987.

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Research Overview

Colin Baxter's research career has centered on theoretical aspects of quantum optics and quantum electrodynamics, with a particular focus on the interaction between light and matter. His work spans from foundational questions of gauge invariance to practical implications such as radiation pressure and photon drag effects. The publications listed above chart a coherent trajectory from early investigations of gauge transformations in non-relativistic QED to later explorations of topological features in trapped cold ions and Bose gases.

The unifying theme is a rigorous application of mathematical physics to problems at the interface of atomic physics and electromagnetic theory. Baxter's contributions have clarified how gauge choices affect physical predictions, illuminated the canonical formulation of photon pressure, and revealed deep connections between quantum mechanics and topology in low-dimensional systems.

Gauge Invariance and Quantum Electrodynamics

A significant portion of Baxter's early work addressed the role of gauge invariance in non-relativistic quantum electrodynamics. In collaboration with M. Babiker and R. Loudon, he developed a hybrid gauge transformation for coupled atom-field systems (Journal of Physics A, 1989) and explored the consequences of mixing the p·A and q·E interaction terms (Journal of Modern Optics, 1990). These studies demonstrated that physical observables remain invariant under gauge transformations, provided that the full Hamiltonian is considered, including counter-rotating terms often neglected in the rotating wave approximation.

His Ph.D. thesis (University of Essex, 1991) and subsequent papers, such as "Alpha-Lorentz Gauge QED" (Annals of Physics, 1991) and "Canonical Approach to Photon Pressure" (Physical Review A, 1993), further extended these ideas. Baxter showed that a consistent canonical quantization of the electromagnetic field in the presence of matter requires careful treatment of gauge degrees of freedom. This work laid the foundation for understanding radiation forces on atoms, which became a major theme of his later research.

Radiation Pressure and Momentum Transfer

Baxter made notable contributions to the theory of radiation forces and momentum transfer in dielectrics, often in collaboration with Rodney Loudon and Stephen Barnett. The 2005 paper "Radiation Pressure and Momentum Transfer in Dielectrics: The Photon Drag Effect" (Physical Review A) clarified the controversial Abraham-Minkowski dilemma by analyzing the momentum of light inside a dielectric medium and its transfer to the medium itself. The photon drag effect, where the momentum of photons imparts a drag force on electric charges, was shown to be consistent with the canonical approach.

Earlier, the 1993 paper "Theory of Radiation Forces and Momenta for Mobile Atoms in Light Fields" (Physical Review A, with Lembessis, Babiker, and Loudon) provided a comprehensive framework for calculating radiation forces on moving atoms, with implications for laser cooling and atom optics. Baxter's 1995 Physical Review A paper "Radiation Pressure and Coherent States of Two-Level Atoms" examined the radiation pressure from a quantum perspective, highlighting the role of coherence in enhancing or suppressing forces.

Understanding these momentum transfers is critical for applications in optical trapping, atom interferometry, and the development of quantum technologies. The precision of these theories has been validated by numerous experiments, cementing the canonical approach as a standard tool.

Topological Effects and Cold Atoms

In the late 1990s and early 2000s, Baxter turned to topological aspects of quantum systems. The paper "Topological Equivalence in the Theory of a Trapped Cold Ion" (Journal of Modern Optics, 1998, with Loudon) investigated how the topology of the trapping potential influences the quantum states of a single cold ion, revealing equivalences with other two-dimensional systems. This line of inquiry continued in "Cold Rydberg Atoms as Realizable Analogs of Chern-Simons Theory" (Physical Review Letters, 1995), where Baxter proposed that cold Rydberg atoms could simulate anyons and emergent gauge theories, a precursor to modern quantum simulation.

Further work on Bose-Einstein condensates, "Coherence Length for a Trapped Bose Gas" (Journal of Physics B, 2000, with Barnett, Franke-Arnold, and Arnold), characterized the coherence properties of ultracold gases, essential for understanding phase transitions and interference phenomena. Preprints on "Topological Eigenfunctions in Two-Dimensions" and related topics indicate a broader interest in the interplay of geometry and quantum mechanics.

Impact and Collaboration

Baxter's publications have appeared in leading peer-reviewed journals, reflecting their impact on the field. Collaborations with distinguished physicists such as Rodney Loudon, Stephen Barnett, and Mohamed Babiker highlight the breadth of his network. The recognition of his work extends to contributions beyond journal papers: conference presentations at venues like CLEO/Europe and ICAP, and technical reports, underscore an active engagement with the scientific community.

While Baxter has not posted preprints to standard repositories, the listed preprints indicate ongoing research that likely influenced later publications. The technical report on "Radiation from Cellphone Transmitter Towers" (2003) demonstrates an application of electromagnetic theory to public health concerns, showing the practical relevance of his expertise.

Further Resources

For a complete listing of Colin Baxter's academic background and other writings, please visit the Academic Overview page. Additional bibliographical data and physics-related articles can be found in the Bibliographical Data section. Specific articles of interest are also collected under Physics Articles, and a selection of influential books is listed in Physics Books. Other miscellaneous resources are available at Physics Others. For biographical information, see About Colin Baxter.