research

Quantum Theory

I am drawn to the geometric and topological side of quantum theory, especially to those situations in which electromagnetic interactions seem to conspire with geometry and topology. Gauge structure, nonlocality, electromagnetic duality and magnetic charge all belong to this picture. To me, the geometrisation of interaction is one of the most elegant ideas in quantum theory.

The Aharonov–Bohm effect in a closed flux line
An exact formulation of the Aharonov–Bohm effect for a closed magnetic flux line, providing a natural idealisation of a toroidal magnet. The AB phase is determined by a linking number rather than a winding number, making its topological character explicit and allowing the local and nonlocal interpretations of the effect to be examined from a different perspective.
Ricardo Heras, The European Physical Journal Plus, 137, 641 (2022)
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The quantum phase of a dyon
A duality-invariant quantum phase acquired by a dyon encircling confined electric and magnetic fluxes. The construction unifies the Aharonov–Bohm phase with its electromagnetic dual and shows how topology, nonlocality and electric–magnetic duality can be incorporated within a single quantum-mechanical framework.
Ricardo Heras, The European Physical Journal Plus, 138, 329 (2023)
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Dyons with phase δθ = nθ
An extension of the topological dyon phase obtained by combining electromagnetic duality with the Witten effect. The resulting phase is proportional to the vacuum angle θ and becomes quantised as δθ = nθ, establishing a connection between dyonic quantum phases, CP violation and an Abelian form of the θ-vacua.
Ricardo Heras, The European Physical Journal Plus, 138, 991 (2023)
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Dirac Quantization Condition Holds with Nonzero Photon Mass
An investigation of whether the Dirac quantisation condition survives when the photon is allowed to have a nonzero mass. Although the usual electromagnetic-angular-momentum argument is then modified by screening, the gauge-theoretic argument survives: magnetic charge cannot be screened, and the invisibility of the Dirac string or the equivalent Wu–Yang gauge transition continues to require charge quantisation.
Alfred S. Goldhaber and Ricardo Heras, arXiv:1710.03321 (2017)
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Classical Electrodynamics

I am interested in what classical electrodynamics can reveal when electromagnetic systems are considered in non-simply connected spaces. In particular, I have explored how topology, nonlocality, electromagnetic angular momentum and electric–magnetic duality become intertwined even within a classical field theory.

Can classical electrodynamics predict nonlocal effects?
A study of electromagnetic angular momentum in the configuration formed by a charge encircling a confined magnetic flux. Although classical electrodynamics is fundamentally local, the resulting angular momentum is topological, depends on a winding number and connects spatially separated electromagnetic regions. Its magnitude provides a classical counterpart of the Aharonov–Bohm phase.
José A. Heras and Ricardo Heras, The European Physical Journal Plus, 136, 847 (2021)
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Topology, nonlocality and duality in classical electrodynamics
An extension of topological electromagnetic angular momentum to systems containing both electric and magnetic charges and fluxes. A dyon interacting with a dual solenoid gives rise to an angular momentum that is simultaneously topological, nonlocal and invariant under electromagnetic duality transformations, unifying electric and magnetic versions of the construction.
José A. Heras and Ricardo Heras, The European Physical Journal Plus, 137, 157 (2022)
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High-Energy Astrophysics

I no longer work on neutron-star astrophysics, but it was the subject through which I first found my way into physics. My early work explored the violent birth of neutron stars, particularly the possible connections between magnetic-field evolution, rapid rotation, magnetorotational instabilities and the unusually large space velocities observed in pulsars.

Magnetorotational instabilities and pulsar kick velocities
A model connecting the large observed space velocities of neutron stars with magnetorotational instabilities occurring shortly after their birth. The proposed mechanism converts energy stored in differential rotation into radiation and translational kinetic energy on an Alfvén timescale, linking pulsar kicks with millisecond rotation and very strong magnetic fields.
Ricardo Heras, New Astronomy, 43, 6–9 (2016)
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Birth accelerations of neutron stars
An early model of neutron-star birth in which rotational-energy loss, magnetic-field decay and the acquisition of space velocity are treated as interconnected processes. The resulting energy balance suggests that newly born neutron stars may undergo extremely large accelerations during a short and highly energetic stage of their evolution.
Ricardo Heras, Proceedings of the International Astronomical Union, S291, 399–401 (2013)
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