arXiv subjects

Juan F. Marín

Publications and source records attributed to Juan F. Marín.

14 recordsLinked to original sources

arXiv2025

Quasi-fluxon bubble dynamics in a rapid oscillatory microwave field

In this article, we numerically study the dynamics of a two-dimensional quasi-fluxon bubble in an oscillatory regime stabilized by a localized annular force under a rapidly oscillating microwave field. The bubble exhibits two distinctly dynamical regimes. At first, the oscillation of the bubble wall scales up linearly with the microwave field frequency until it reaches a cutoff, after which it detaches from the external field, returning to its natural oscillation frequency. The amplitude of the quasi-fluxon oscillations is inversely proportional to the square of the microwave field frequency. Following a simplified model based on the Kapitza approach, we proved that this dynamical behavior is characteristic of systems with a harmonic potential subjected to a rapidly oscillating field. Possible applications of microwave detection are discussed.

nlin.PS↗

arXiv2024

Highly-enhanced propagation of long-range kinks in heterogeneous media

We investigate a field-theoretical model that describes the interaction between kinks and antikinks and between kinks and other heterogeneous fields and impurities. We show that the long-range kink can tunnel through a barrier created by heterogeneous fields and impurities even when the energy of the center of mass of the kink is less than the height of the energy barrier. We also study the conditions under which the kink can pass freely through a disordered medium. We introduce the concept of "effective translational symmetry". We compare our results with those from recent papers published in this journal, where the Bogomol'nyi-Prasad-Sommerfield property is discussed.

nlin.PS↗

arXiv2024

A synchrotron-like pumped ring resonator for water waves

The wave-like behaviour of matter in quantum physics has spurred insightful analogies between the dynamics of particles and waves in classical systems. In this study, drawing inspiration from synchrotrons that resonate to accelerate ions along a closed path, we introduce the concept of a synchrowave: a waveguide designed to generate and sustain travelling water waves within a closed annular channel. In analogy to unavoidable energy losses in conventional particle accelerators due to electromagnetic radiation and inelastic collisions, the system displays undesired water-wave dampening, which we address through the synchronised action of underwater wavemakers. Our analogies extend the resonance mechanisms of synchrotrons to generate gravity waves in closed waveguides efficiently. A proof-of-concept experiment at a laboratory scale demonstrates the unique capability of this technique to build up anomalously large travelling waves displaying a flat response in the long-wave limit. Besides quantifying the performance of wave generation, our findings offer a framework for both industrial and computational applications, opening up unexplored possibilities in hydraulics, coastal science and engineering. In a broader context, our experimental apparatus and methods highlight the versatility of a simple yet powerful concept: a closed-path continuous-energy-pumping scheme to effectively harvest prominent resonant responses within wave-supporting systems displaying weak dissipation.

physics.flu-dyn↗

arXiv2022

Fluid motion for reducing the bounce of partially filled containers

Certain spatial distributions of water inside partially filled containers can significantly reduce the bounce of the container. In experiments with containers filled to a volume fraction $ϕ$, we show that rotation offers control and high efficiency in setting such distributions and, consequently, in altering bounce markedly. High-speed imaging evidences the physics of the phenomenon and reveals a rich sequence of fluid-dynamics processes, which we translate into a model that captures our overall experimental findings.

physics.flu-dyn↗

arXiv2022

Mutation and SARS-CoV-2 strain competition under vaccination in a modified SIR model

The crisis caused by the COVID-19 outbreak around the globe raised an increasing concern about the ongoing emergence of variants of SARS-CoV-2 that may evade the immune response provided by vaccines. New variants appear due to mutation, and as the cases accumulate, the probability of the emergence of a variant of concern increases. In this article, we propose a modified SIR model with waning immunity that captures the competition of two strain classes of an infectious disease under the effect of vaccination with a highly contagious and deadly strain class emerging from a prior strain due to mutation. When these strains compete for a limited supply of susceptible individuals, changes in the efficiency of vaccines may affect the behaviour of the disease in a non-trivial way, resulting in complex outcomes. We characterise the parameter space including intrinsic parameters of the disease, and using the vaccine efficiencies as control variables. We find different types of transcritical bifurcations between endemic fixed points and a disease-free equilibrium and identify a region of strain competition where the two strain classes coexist during a transient period. We show that a strain can be extinguished either due to strain competition or vaccination, and we obtain the critical values of the efficiency of vaccines to eradicate the disease. Numerical studies using parameters estimated from publicly reported data agree with our theoretical results. Our mathematical model could be a tool to assess quantitatively the vaccination policies of competing and emerging strains using the dynamics in epidemics of infectious diseases.

q-bio.PE↗

arXiv2022

Pedal underwater motion triggers highly-peaked resonance on water waves

Pedal wavemakers that generate surface gravity waves through bed orbital motion have been shown to produce particle-excursion patterns that mimic deep-water wave behaviour but in finite-depth channels. In this article, we report that gravity waves in a general viscous fluid can resonate through the action of pedal wavemakers. We analyse the linear response of waves in an infinite channel in terms of the displacement amplitude, frequency, and wavelength of the bottom action. We show that the system behaves as a long-pass filter in space and a high-pass filter in time with a sharp resonance affected by viscosity. Furthermore, we propose a protocol to design deep gravity waves with an on-demand wavelength in a finite-depth water channel. Our theoretical framework agrees with numerical simulations using Smoothed Particle Hydrodynamics. Our results thus quantify the performance of pedal wavemakers and provide essential formulas for industrial and computational applications of the pedal wavemaking technique, useful both in hydraulics and coastal engineering problems.

physics.flu-dyn↗

arXiv2021

Drift instabilities in localised Faraday patterns

Nature is intrinsically heterogeneous, and remarkable phenomena can only be observed in the presence of intrinsically nonlinear heterogeneities. Spontaneous pattern formation in nature has fascinated humankind for centuries, and the understanding of the underlying symmetry-breaking instabilities has been of longstanding scientific interest. In this article, we provide theoretical and experimental evidence that heterogeneities can generate convection (drift instabilities) in the amplitude of localised patterns. We derive a minimal theoretical model describing the growth of localised Faraday patterns under heterogeneous parametric drive, unveiling the presence of symmetry-breaking nonlinear gradients. The model reveals new dynamics in the phase of the underlying patterns, exhibiting convective instabilities when the system crosses a secondary bifurcation point. We discuss the impact of our results in the understanding of convective instabilities induced by heterogeneities in generic nonlinear extended systems far from equilibrium.

nlin.PS↗

arXiv2019

Shape of a recoiling liquid filament

We study the capillary retraction of a Newtonian semi-infinite liquid filament through analytical methods. We derive a long-time asymptotic-state expansion for the filament profile using a one-dimensional free-surface slender cylindrical flow model based on the three-dimensional axisymmetric Navier-Stokes equations. The analysis identifies three distinct length and time scale regions in the retraction domain: a steady filament section, a growing spherical blob, and an intermediate matching zone. We show that liquid filaments naturally develop travelling capillary waves along their surface and a neck behind the blob. We analytically prove that the wavelength of the capillary waves is approximately 3.63 times the filament's radius at the inviscid limit. Additionally, the waves' asymptotic wavelength, decay length, and the minimum neck size are analysed in terms of the Ohnesorge number. Finally, our findings are compared with previous results from the literature and numerical simulations in Basilisk obtaining a good agreement. This analysis provides a full picture of the recoiling process going beyond the classic result of the velocity of retraction found by Taylor and Culick.

physics.flu-dyn↗

arXiv2019

Stability of bubble-like fluxons in disk-shaped Josephson junctions in the presence of a coaxial dipole current

We investigate analytically and numerically the stability of bubble-like fluxons in disk-shaped heterogeneous Josephson junctions. Using ring solitons as a model of bubble fluxons in the two-dimensional sine-Gordon equation, we show that the insertion of coaxial dipole currents prevents their collapse. We characterize the onset of instability by introducing a single parameter that couples the radius of the bubble fluxon with the properties of the injected current. For different combination of parameters, we report the formation of stable oscillating bubbles, the emergence of internal modes, and bubble breakup due to internal mode instability. We show that the critical germ depends on the ratio between its radius and the steepness of the wall separating the different phases in the system. If the steepness of the wall is increased (decreased), the critical radius decreases (increases). Our theoretical findings are in good agreement with numerical simulations. We discuss applications in quantum information technologies.

nlin.PS↗

arXiv2019

Localized Faraday patterns under heterogeneous parametric excitation

Faraday waves are a classic example of a system in which an extended pattern emerges under spatially uniform forcing. Motivated by systems in which uniform excitation is not plausible, we study both experimentally and theoretically the effect of heterogeneous forcing on Faraday waves. Our experiments show that vibrations restricted to finite regions lead to the formation of localized subharmonic wave patterns and change the onset of the instability. The prototype model used for the theoretical calculations is the parametrically driven and damped nonlinear Schrödinger equation, which is known to describe well Faraday-instability regimes. For an energy injection with a Gaussian spatial profile, we show that the evolution of the envelope of the wave pattern can be reduced to a Weber-equation eigenvalue problem. Our theoretical results provide very good predictions of our experimental observations provided that the decay length scale of the Gaussian profile is much larger than the pattern wavelength.

nlin.PS↗

arXiv2019

New combinational therapies for cancer using modern statistical mechanics

We investigate a new dynamical system that describes tumor-host interaction. The equation that describes the untreated tumor growth is based on non-extensive statistical mechanics. Recently, this model has been shown to fit successfully exponential, Gompertz, logistic, and power-law tumor growths. We have been able to include as many hallmarks of cancer as possible. We study also the dynamic response of cancer under therapy. Using our model, we can make predictions about the different outcomes when we change the parameters, and/or the initial conditions. We can determine the importance of different factors to influence tumor growth. We discover synergistic therapeutic effects of different treatments and drugs. Cancer is generally untreatable using conventional monotherapy. We consider conventional therapies, oncogene-targeted therapies, tumor-suppressors gene-targeted therapies, immunotherapies, anti-angiogenesis therapies, virotherapy, among others. We need therapies with the potential to target both tumor cells and the tumors' microenvironment. Drugs that target oncogenes and tumor-suppressor genes can be effective in the treatment of some cancers. However, most tumors do reoccur. We have found that the success of the new therapeutic agents can be seen when used in combination with other cancer-cell-killing therapies. Our results have allowed us to design a combinational therapy that can lead to the complete eradication of cancer.

physics.bio-ph↗

arXiv2018

Fate of the true-vacuum bubbles

We investigate the bounce solutions in vacuum decay problems. We show that it is possible to have a stable false vacuum in a potential that is unbounded from below.

hep-th↗

arXiv2017

Generation of soliton bubbles in a sine-Gordon system with localised inhomogeneities

Nonlinear wave propagation plays a crucial role in the functioning of many physical and biophysical systems. In the propagation regime, disturbances due to the presence of local external perturbations, such as localised defects or boundary interphase walls have gained great attention. In this article, the complex phenomena that occur when sine-Gordon line solitons collide with localised inhomogeneities are investigated. By a one-dimensional theory, it is shown that internal modes of two-dimensional sine-Gordon solitons can be activated depending on the topological properties of the inhomogeneities. Shape mode instabilities cause the formation of bubble-like and drop-like structures for both stationary and travelling line solitons. It is shown that such structures are formed and stabilised by arrays of localised inhomogeneities distributed in space. Implications of the observed phenomena in physical and biological systems are discussed.

nlin.PS↗

arXiv2017

Bubble-like structures generated by activation of internal shape modes in two-dimensional sine-Gordon line solitons

Nonlinear waves that collide with localized defects exhibit complex behavior. Apart from reflection, transmission, and annihilation of an incident wave, a local inhomogeneity can activate internal modes of solitons, producing many impressive phenomena. In this work, we investigate a two-dimensional sine-Gordon model perturbed by a family of localized forces. We observed the formation of bubble-like and drop-like structures due to local internal shape modes instabilities. We describe the formation of such structures on the basis of a one-dimensional theory of activation of internal modes of sG solitons. An interpretation of the observed phenomena, in the context of phase transitions theory, is given. Implications in Josephson junctions with a current dipole device are discussed.

nlin.PS↗