EPL

Touzo, L.; Le Doussal, P.

doi: 10.1209/0295-5075/ad222bpmid: N/A

We consider N run-and-tumble particles in one dimension interacting via a linear 1D Coulomb potential, an active version of the rank diffusion problem. It was solved previously for N = 2 leading to a stationary bound state in the attractive case. Here the evolution of the density fields is obtained in the large-N limit in terms of two coupled Burger's type equations. In the attractive case the exact stationary solution describes a non-trivial N-particle bound state, which exhibits transitions between a phase where the density is smooth with infinite support, a phase where the density has finite support and exhibits “shocks”, i.e., clusters of particles, at the edges, and a fully clustered phase. In the presence of an additional linear potential, the phase diagram, obtained for either sign of the interaction, is even richer, with additional partially expanding phases, with or without shocks. Finally, a general self-consistent method is introduced to treat more general interactions. The predictions are tested through extensive numerical simulations.

Costa, Rafael L. J.; Sobreiro, Rodrigo F.

doi: 10.1209/0295-5075/ad229dpmid: N/A

In this work we consider a fermionic quantum gas within a Lorentz-violating background at finite temperature. We derive the effective action within path integral formalism considering the interaction of external electromagnetic field and Lorentz-violating background fields with quantum fermions. To introduce the temperature effects, we employ the Matsubara formalism. Comments about the corresponding phenomenology are also made.

Jirón, Andrés G.; Obispo, Angel E.; Espinoza Loayza, J. D.; Quispe, Juan Carlos; Castro, L. B.

doi: 10.1209/0295-5075/ad2946pmid: N/A

This study investigates the production of neutral scalar boson pairs in static electromagnetic fields resulting from Lorentz-symmetry violation (LSV), with a focus on the parity-even sector of the CPT-even photon sector in the Standard Model Extension (SME). Utilizing a cross-configuration involving inhomogeneous static electric fields and homogeneous static magnetic fields, the analysis of the probability of bosons pair production identifies three different regimes determined by a critical magnetic field. Below the critical value, creation is exponentially suppressed; at the critical value, the number density of created bosons remains constant, and above the critical field, there is exponential amplification. This behavior prompts an additional investigation using von Neumann entanglement entropy to analyze fluctuations in the bosonic vacuum.

Fan, Yaning; Wang, Cheng; Jiang, Linfeng; Sun, Chao; Calzavarini, Enrico

doi: 10.1209/0295-5075/ad2d15pmid: N/A

Understanding the dynamics of material objects advected by turbulent flows is a long-standing question in fluid dynamics. In this perspective article we focus on the characterization of the statistical properties of non-interacting finite-sized massive spherical particles advected by a vigorous turbulent flow. We study the fluctuations and temporal correlations of particle accelerations and explore their behaviours with respect to the particle size and the particle mass density by means of fully resolved numerical simulations. We observe that the measured trends cannot be interpreted as the simple multiplicative combination of the two dominant effects: the spatial filtering of fluid accelerations and the added-mass–adjusted fluid-to-particle density ratio. We argue that other hydrodynamical forces or effects, e.g., preferential flow sampling, have still a significant role even at the largest particle sizes, which reach here the integral scale of turbulence.

Ekuma, C. E.

doi: 10.1209/0295-5075/ad26b0pmid: N/A

Lattice thermal-transport properties of heavy-fermion YbT2Zn20-based (T = Co, Rh, and Ir) 1-2-20 compounds are calculated with the single-mode relaxation-time approximation and the full solution of the linearized phonon Boltzmann transport equation from first-principles anharmonic phonon calculations. We predict low lattice thermal conductivity κLwith a maximum value of ∼24.16  ·K at 85.14 K, 137.29  ·K at 9.67 K, and 23.55  ·K at 67.50 K and ∼12.02, 40.04, and 10.30  ·K at room temperature for YbCo2Zn20, YbRh2Zn20, and YbIr2Zn20, respectively. Based on the analysis of the cumulative κLas a function of the phonon mean free path and the frequency-dependent joint density of states at various temperatures, we attribute the low κLto a rattling mode with an average characteristic rattling frequency that enhanced phonon scattering processes, which reduced the phonon mean free paths, suppressed the phonon lifetime, and enhanced the probability of three-phonon scattering events. The predicted low κL, especially in YbCo2Zn20 and YbIr2Zn20, makes them promising candidate materials for thermoelectric applications and thermal management.

Parmar, Vaibhav Raj Singh; Bandyopadhyay, Ranjini

doi: 10.1209/0295-5075/ad2d13pmid: N/A

The growth of interfacial instabilities during fluid displacements can be driven by gradients in pressure, viscosity and surface tension, and by applying external fields. Since displacements of non-Newtonian fluids such as polymer solutions, colloidal and granular slurries are ubiquitous in natural and industrial processes, understanding the growth mechanisms and fully developed morphologies of interfacial patterns involving non-Newtonian fluids is extremely important. In this perspective, we focus on displacement experiments, wherein competitions between capillary, viscous, elastic and frictional forces drive the onset and growth of primarily viscous fingering instabilities in confined geometries. We conclude by highlighting several exciting open problems in this research area.

Chen, Fengyi; Du, Qiujiao; Liu, Fengming; Peng, Pai

doi: 10.1209/0295-5075/ad26afpmid: N/A

In this letter, we report a theoretical study for the conversions between extensional and flexural modes for Lamb waves. The incident extensional waves can be completely converted into reflected flexural waves, or vice versa. The used structure is oblique anisotropic tri-component resonators with locally dipolar resonators. Without special optimization designs, the thickness of conversion device is much smaller than the working wavelengths (1/150 and 1/15 for the extensional and flexural waves, respectively). Our proposed design is more feasible for low-frequency application scenarios.

Oikonomou, V. K.; Tsyba, Pyotr; Razina, Olga

doi: 10.1209/0295-5075/ad239cpmid: N/A

In this work we shall prove that the tensor spectral index of the primordial tensor perturbations for GW170817-compatible Einstein-Gauss-Bonnet theories, takes the approximate simplified form at leading order, with being a function of the scalar field which depends on the scalar field potential and the second derivative of the scalar-Gauss-Bonnet coupling . With our analysis we aim to provide a definitive criterion for selecting Einstein-Gauss-Bonnet models that can provide a blue-tilted inflationary phenomenology, by simply looking at the scalar potential and the scalar-Gauss-Bonnet coupling. We shall prove this using two distinct approaches and as we show the tilt of the tensor spectral index is determined by the values of the potential and of scalar-Gauss-Bonnet coupling at first horizon crossing. Specifically the blue-tilted tensor spectral index can occur when at first horizon crossing.

Zhao, Liuxian; Zhuang, Xuxu; Guo, Hao; Bi, Chuanxing; Sun, Zhaoyong

doi: 10.1209/0295-5075/ad2871pmid: N/A

In this paper, a novel structural Luneburg lens with local resonators is proposed. This lens allows the realization of subwavelength focusing in low-frequency range. The lens is achieved by graded refractive index from the lens's centre to the outer surface. Numerical simulations are conducted to obtain data on wave propagation waveform, maximum displacement amplitude, and full width at half-maximum (FWHM) of the lens's focal region. The results show that a broadband frequency range can be achieved for subwavelength focusing. This provides a straightforward and adaptable method for designing the structural Luneburg lens for numerous applications.

Wang, Kang-Jia; Shi, Feng

doi: 10.1209/0295-5075/ad219dpmid: N/A

The (2+1)-dimensional Boiti-Leon-Manna-Pempinelli equation (BLMPE) is explored in this letter. The multi-soliton solutions (MSSs) are probed via the Hirota bilinear form which is extracted by taking advantage of the Cole-Hopf transform. The soliton molecules (SMs) on the different planes such as the (x,y)-, (x,t)- and (y,t)-planes are investigated via assigning the velocity resonance mechanisms. The dynamic characteristics of the results are unveiled graphically to show the corresponding physical behaviors.