Hojman, S. A., Asenjo, F. A., MoyaCessa, H. M., & SotoEguibar, F. (2021). Bohm potential is real and its effects are measurable. Optik, 232, 166341.
Abstract: We analyze Bohm potential effects both in the realms of Quantum Mechanics and Optics, as well as in the study of other physical phenomena described in terms of classical and quantum wave equations. We approach this subject by using theoretical arguments as well as experimental evidence. We find that the effects produced by Bohm potential are both theoretically responsible for the early success of Quantum Mechanics correctly describing atomic and nuclear phenomena and, more recently, by confirming surprising accelerating behavior of free waves and particles experimentally, for instance.

Hojman, S. A., & Asenjo, F. A. (2020). A new approach to solve the onedimensional Schrodinger equation using a wavefunction potential. Phys. Lett. A, 384(36), 7 pp.
Abstract: A new approach to find exact solutions to onedimensional quantum mechanical systems is devised. The scheme is based on the introduction of a potential function for the wavefunction, and the equation it satisfies. We recover known solutions as well as to get new ones for both free and interacting particles with wavefunctions having vanishing and nonvanishing Bohm potentials. For most of the potentials, no solutions to the Schrodinger equation produce a vanishing Bohm potential. A (large but) restricted family of potentials allows the existence of particular solutions for which the Bohm potential vanishes. This family of potentials is determined, and several examples are presented. It is shown that some quantum, such as accelerated Airy wavefunctions, are due to the presence of nonvanishing Bohm potentials. New examples of this kind are found and discussed. (C) 2020 Elsevier B.V. All rights reserved.

Hojmann, S. A., & Asenjo, F. A. (2020). Quantum particles that behave as free classical particles. Phys. Rev. A, 102(5), 052211.
Abstract: The existence of nonvanishing Bohm potentials, in the MadelungBohm version of the Schrödinger equation, allows for the construction of particular solutions for states of quantum particles interacting with nontrivial external potentials that propagate as free classical particles. Such solutions are constructed with phases which satisfy the classical HamiltonJacobi for free particles and whose probability densities propagate with constant velocity, as free classical particles do.

Asenjo, F. A., & Hojman, S. A. (2020). Casimir force induced by electromagnetic wave polarization in Kerr, Godel and BianchiI spacetimes. Eur. Phys. J. C, 80(11), 7 pp.
Abstract: Electromagnetic waves propagation on either rotating or anisotropic spacetime backgrounds (such as Kerr and Gödel metrics, or Bianchi�I metric) produce a reduction of the magnitude of Casimir forces between plates. These
curved spacetimes behave as chiral or birefringent materials producing dispersion of electromagnetic waves, in such a way that right� and left�circularly polarized light waves propagate with different phase velocities. Results are explicitly calculated for discussed cases. The difference on the wavevectors of the two polarized electromagnetic waves produces an abatement of a Casimir force which depends on the interaction between the polarization of electromagnetic
waves and the properties of the spacetime.

Hojman, S. A., & Asenjo, F. A. (2020). Phenomenological dynamics of COVID19 pandemic: Metaanalysis for adjustment parameters. Chaos, 30(10), 12 pp.
Abstract: We present a phenomenological procedure of dealing with the COVID19 (coronavirus disease 2019) data provided by government health agencies of 11 different countries. Usually, the exact or approximate solutions of susceptibleinfectedrecovered (or other) model(s) are obtained fitting the data by adjusting the timeindependent parameters that are included in those models. Instead of that, in this work, we introduce dynamical parameters whose timedependence may be phenomenologically obtained by adequately extrapolating a chosen subset of the daily provided data. This phenomenological approach works extremely well to properly adjust the number of infected (and removed) individuals in time for the countries we consider. Besides, it can handle the subepidemic events that some countries may experience. In this way, we obtain the evolution of the pandemic without using any a priori model based on differential equations.

Caerols, H., & Asenjo, F. A. (2020). Estimating the MoontoEarth Radius Ratio with a Smartphone, a Telescope, and an Eclipse. Phys. Teach., 58(7), 497–501.
Abstract: From ancient times, the different features of planets and moons have created a huge interest. Aristarchus was one of the first to study the relative relations among Earth, Moon, and Sun. This interest has remained until today, and therefore it is always relevant to make this knowledge more appealing to the younger generations. Nowadays, smartphone technology has become an important tool to teach physics, and this gives us a huge opportunity to bring science closer to students in a simpler manner. In this work, we show how simple photographs of a partial lunar eclipse are sufficiently good to estimate the ratio between the Moon and Earth radii. After taking the photographs, the procedure for the calculation is straightforward and it can be reproduced easily in a one–hour class

Comisso, L., & Asenjo, F. A. (2020). Generalized magnetofluid connections in a curved spacetime. Phys. Rev. D, 102(2), 8 pp.
Abstract: The ideal magnetohydrodynamic theorem on the conservation of the magnetic connections between plasma elements is extended to nonideal relativistic plasmas in curved spacetime. The existence of generalized magnetofluid connections that are preserved by the plasma dynamics is formalized by means of a covariant connection equation that includes different nonideal effects. These generalized connections are constituted by 2dimensional hypersurfaces, which are linked to an antisymmetric tensor field that unifies the electromagnetic and fluid fields. They can be interpreted in terms of generalized magnetofluid vorticity field lines by considering a 3 + 1 foliation of spacetime and a time resetting projection that compensates for the loss of simultaneity between spatially separated events. The worldshects of the generalized magnetofluid vorticity field lines play a fundamental role in the plasma dynamics by prohibiting evolutions that do not preserve the magnetofluid connectivity.

Hojman, S. A., & Asenjo, F. A. (2020). Classical and Quantum Dispersion Relations. Phys. Scr., 95(8), 7 pp.
Abstract: It is showed that, in general, classical and quantum dispersion relations are different due to the presence of the Bohm potential. There are exact particular solutions of the quantum (wave) theory which obey the classical dispersion relation, but they differ in the general case. The dispersion relations may also coincide when additional assumptions are made, such as WKB or eikonal approximations, for instance. This general result also holds for nonquantum wave equations derived from classical counterparts, such as in ray and wave optics, for instance. Explicit examples are given for covariant scalar, vectorial and tensorial fields in flat and curved spacetimes.

Asenjo, F. A., & Mahajan, S. M. (2020). Resonant interaction between dispersive gravitational waves and scalar massive particles. Phys. Rev. D, 101(6), 4 pp.
Abstract: The KleinGordon equation is solved in the curved background spacetime created by a dispersive gravitational wave. Unlike solutions of perturbed Einstein equations in vacuum, dispersive gravitational waves do not travel exactly at the speed of light. As a consequence, the gravitational wave can resonantly exchange energy with scalar massive particles. Some details of the resonant interaction are displayed in a calculation demonstrating how relativistic particles (modeled by the KleinGordon equation), feeding on such gravitational waves, may be driven to extreme energies.

Hojman, S. A., & Asenjo, F. A. (2020). Dual wavefunctions in twodimensional quantum mechanics. Phys. Lett. A, 384(13), 5 pp.
Abstract: It is shown that the Schrodinger equation for a large family of pairs of twodimensional quantum potentials possess wavefunctions for which the amplitude and the phase are interchangeable, producing two different solutions which are dual to each other. This is a property of solutions with vanishing Bohm potential. These solutions can be extended to threedimensional systems. We explicitly calculate dual solutions for physical systems, such as the repulsive harmonic oscillator and the twodimensional hydrogen atom. These dual wavefunctions are also solutions of an analogue optical system in the eikonal limit. In this case, the potential is related to the refractive index, allowing the study of this twodimensional dual wavefunction solutions with an optical (analogue) system. (C) 2020 Elsevier B.V. All rights reserved.

Asenjo, F. A., & Hojman, S. A. (2019). Correspondence between dark energy quantum cosmology and Maxwell equations. Eur. Phys. J. C, 79(9), 5 pp.
Abstract: A FriedmannRobertsonWalker cosmology with dark energy can be modelled using a quintessence field. That system is equivalent to a relativistic particle moving on a twodimensional conformal spacetime. When the quintessence behaves as a free massless scalar field in a Universe with cosmological constant, the quantized version of that theory can lead to a supersymmetric Majorana quantum cosmology. The purpose of this work is to show that such quantum cosmological model corresponds to the Maxwell equations for electromagnetic waves propagating in a medium with specific values for its relative permittivity and relative permeability. The form of those media parameters are calculated, implying that a Majorana quantum cosmology can be studied in an analogue electromagnetic system.

Rubio, C. A., Asenjo, F. A., & Hojman, S. A. (2019). Quantum Cosmologies Under Geometrical Unification of Gravity and Dark Energy. Symmetry, 11(7).
Abstract: A FriedmannRobertsonWalker Universe was studied with a dark energy component represented by a quintessence field. The Lagrangian for this system, hereafter called the FriedmannRobertsonWalkerquintessence (FRWq) system, was presented. It was shown that the classical Lagrangian reproduces the usual two (second order) dynamical equations for the radius of the Universe and for the quintessence scalar field, as well as a (first order) constraint equation. Our approach naturally unified gravity and dark energy, as it was obtained that the Lagrangian and the equations of motion are those of a relativistic particle moving on a twodimensional, conformally flat spacetime. The conformal metric factor was related to the dark energy scalar field potential. We proceeded to quantize the system in three different schemes. First, we assumed the Universe was a spinless particle (as it is common in literature), obtaining a quantum theory for a Universe described by the KleinGordon equation. Second, we pushed the quantization scheme further, assuming the Universe as a Dirac particle, and therefore constructing its corresponding Dirac and Majorana theories. With the different theories, we calculated the expected values for the scale factor of the Universe. They depend on the type of quantization scheme used. The differences between the Dirac and Majorana schemes are highlighted here. The implications of the different quantization procedures are discussed. Finally, the possible consequences for a multiverse theory of the Dirac and Majorana quantized Universe are briefly considered.

Mahajan, S. M., & Asenjo, F. A. (2018). General connected and reconnected fields in plasmas. Phys. Plasmas, 25(2), 7 pp.
Abstract: For plasma dynamics, more encompassing than the magnetohydrodynamical (MHD) approximation, the foundational concepts of “magnetic reconnection” may require deep revisions because, in the larger dynamics, magnetic field is no longer connected to the fluid lines; it is replaced by more general fields (one for each plasma specie) that are weighted combination of the electromagnetic and the thermalvortical fields. We study the twofluid plasma dynamics plasma expressed in two different sets of variables: the twofluid (2F) description in terms of individual fluid velocities, and the onefluid (1F) variables comprising the plasma bulk motion and plasma current. In the 2F description, a Connection Theorem is readily established; we show that, for each specie, there exists a Generalized (Magnetofluid/ElectroVortic) field that is frozenin the fluid and consequently remains, forever, connected to the flow. This field is an expression of the unification of the electromagnetic, and fluid forces (kinematic and thermal) for each specie. Since the magnetic field, by itself, is not connected in the first place, its reconnection is never forbidden and does not require any external agency (like resistivity). In fact, a magnetic field reconnection (local destruction) must be interpreted simply as a consequence of the preservation of the dynamical structure of the unified field. In the 1F plasma description, however, it is shown that there is no exact physically meaningful Connection Theorem; a general and exact field does not exist, which remains connected to the bulk plasma flow. It is also shown that the helicity conservation and the existence of a Connected field follow from the same dynamical structure; the dynamics must be expressible as an ideal Ohm's law with a physical velocity. This new perspective, emerging from the analysis of the post MHD physics, must force us to reexamine the meaning as well as our understanding of magnetic reconnection. Published by AIP Publishing.

Asenjo, F. A., & Moya, P. S. (2019). The contribution of magnetic monopoles to the ponderomotive force. J. Phys. AMath. Theor., 52(25), 13 pp.
Abstract: When magnetic monopoles are assumed to exist in plasma dynamics, the propagation of electromagnetic waves is modified as Maxwell equations acquire a symmetrical structure due to the existence of electric and magnetic charge and current densities. This work presents a theoretical exploration on how far we can push the limits of a plasma theory under the presence of magnetic monopoles. In particular, we study the modification of ponderomotive forces in a plasma composed by electric and magnetic charges. We show that the general ponderomotive force on this plasma depends nontrivially on the magnetic monopoles, through the slow temporal and spatial variations of the electromagnetic field amplitudes. The magnetic charges introduce corrections even if the plasma is unmagnetized. Also, it is shown that the magnetic monopoles also experience a ponderomotive force due to the electrons. This force is in the direction of propagation of the electromagnetic waves.

Asenjo, F. A., & Mahajan, S. M. (2019). Diamagnetic field states in cosmological plasmas. Phys. Rev. E, 99(5), 7 pp.
Abstract: Using a generally covariant electrovortic (magnetofluid) formalism for relativistic plasmas, the dynamical evolution of a generalized vorticity (a combination of the magnetic and kinematic parts) is studied in a cosmological context. We derive macroscopic vorticity and magnetic field structures that can emerge in spatial equilibrium configurations of the relativistic plasma. These fields, however, evolve in time. These magnetic and velocity fields, selfconsistently sustained in a plasma with arbitrary thermodynamics, constitute a diamagnetic state in the expanding universe. In particular, we explore a special class of magnetic and velocity field structures supported by a plasma in which the generalized vorticity vanishes. We derive a highly interesting characteristic of such “superconductorlike” fields in a cosmological plasmas in the radiation era in the early universe. In that case, the fields grow proportional to the scale factor, establishing a deep connection between the expanding universe and the primordial magnetic fields.

Asenjo, F. A., & Comisso, L. (2019). Gravitational electromotive force in magnetic reconnection around Schwarzschild black holes. Phys. Rev. D, 99(6), 7 pp.
Abstract: We analytically explore the effects of the gravitational electromotive force on magnetic reconnection around Schwarzschild black holes through a generalized generalrelativistic magnetohydrodynamic model that retains twofluid effects. It is shown that the gravitational electromotive force can couple to collisionless twofluid effects and drive magnetic reconnection. This is allowed by the departure from quasineutrality in curved spacetime, which is explicitly manifested as the emergence of an effective resistivity in Ohm's law. The departure from quasineutrality is owed to different gravitational pulls experienced by separate parts of the current layer. This produces an enhancement of the reconnecion rate due to purely gravitational effects.

Hojman, S. A., & Asenjo, F. A. (2018). Nongeodesic circular motion of massive spinning test bodies around a Schwarzschild field in the Lagrangian theory. Eur. Phys. J. C, 78(10), 7 pp.
Abstract: Recent interest on studying possible violations of the Equivalence Principle has led to the development of space satellite missions testing it for bodies moving on circular orbits around Earth. This experiment establishes that the validity of the equivalence principle is independent of the composition of bodies. However, the internal degrees of freedom of the bodies (such as spin) were not taken into account. In this work, it is shown exactly that the circular orbit motion of test bodies does present a departure from geodesic motion when spin effects are not negligible. Using a Lagrangian theory for spinning massive bodies, an exact solution for their circular motion is found showing that the nongeodesic behavior manifests through different tangential velocities of the test bodies, depending on the orientation of its spin with respect to the total angular momentum of the satellite. Besides, for circular orbits, spinning test bodies present no tangential acceleration. We estimate the difference of the two possible tangential velocities for the case of circular motion of spinning test bodies orbiting Earth.

Comisso, L., & Asenjo, F. A. (2018). Collisionless magnetic reconnection in curved spacetime and the effect of black hole rotation. Phys. Rev. D, 97(4), 9 pp.
Abstract: Magnetic reconnection in curved spacetime is studied by adopting a generalrelativistic magnetohydrodynamic model that retains collisionless effects for both electronion and pair plasmas. A simple generalization of the standard SweetParker model allows us to obtain the firstorder effects of the gravitational field of a rotating black hole. It is shown that the black hole rotation acts to increase the length of azimuthal reconnection layers, thus leading to a decrease of the reconnection rate. However, when coupled to collisionless thermalinertial effects, the net reconnection rate is enhanced with respect to what would happen in a purely collisional plasma due to a broadening of the reconnection layer. These findings identify an underlying interaction between gravity and collisionless magnetic reconnection in the vicinity of compact objects.

Asenjo, F. A., & Hojman, S. A. (2017). Do electromagnetic waves always propagate along null geodesics? Class. Quantum Gravity, 34(20), 12 pp.
Abstract: We find exact solutions to Maxwell equations written in terms of fourvector potentials in nonrotating, as well as in Gdel and Kerr spacetimes. We show that Maxwell equations can be reduced to two uncoupled secondorder differential equations for combinations of the components of the fourvector potential. Exact electromagnetic waves solutions are written on given gravitational field backgrounds where they evolve. We find that in nonrotating spherical symmetric spacetimes, electromagnetic waves travel along null geodesics. However, electromagnetic waves on Gdel and Kerr spacetimes do not exhibit that behavior.

Asenjo, F. A., Erices, C., Gomberoff, A., Hojman, S. A., & Montecinos, A. (2017). Differential geometry approach to asymmetric transmission of light. Opt. Express, 25(22), 26405–26416.
Abstract: In the last ten years, the technology of differential geometry, ubiquitous in gravitational physics, has found its place in the field of optics. It has been successfully used in the design of optical metamaterials through a technique now known as “transformation optics.” This method, however, only applies for the particular class of metamaterials known as impedance matched, that is, materials whose electric permittivity is equal to their magnetic permeability. In that case, the material may be described by a spacetime metric. In the present work we will introduce a generalization of the geometric methods of transformation optics to situations in which the material is not impedance matched. In such situations, the material or more precisely, its constitutive tensorwill not be described by a metric only. We bring in a second tensor, with the local symmetries of the Weyl tensor, the “Wtensor.” In the geometric optics approximation we show how the properties of the Wtensor are related to the asymmetric transmission of the material. We apply this feature to the design of a particularly interesting set of asymmetric materials. These materials are birefringent when light rays approach the material in a given direction, but behave just like vacuum when the rays have the opposite direction with the appropriate polarization (or, in some cases, independently of the polarization). (C) 2017 Optical Society of America
