Using a numerically exact master equation, we demonstrate that two qubits, coupled solely through a shared damped, driven cavity, can become correlated. The drive influences both the amount and the type of correlation. For parametric, coherent, and resonantly modulated drives, the qubits develop quantum discord that increases with cavity temperature, while the logarithmic negativity remains numerically zero. This indicates the presence of discord without entanglement. In contrast, a time-modulated parametric drive is the only one that generates genuine two-qubit entanglement, achieving E_𝒩≃ 0.15 and concurrence ≃ 0.16 at (, γ) = (0.3, 0.2), which rises to E_𝒩≃ 0.32 in the weak-coupling, moderate-damping region. Heating eventually destroys this entanglement around n_th≃ 0.2, while discord continues to grow, resulting in a temperature-driven transition from entanglement to discord within a single drive. Moreover, the parametric drive offers the best protection for single-qubit coherence, unlike the coherent and modulated drives. An adiabatic-elimination model indicates that the cavity generates an effective coupling and a collective dephasing channel, both of which increase with temperature, explaining the observed discord without entanglement.

We analyze the interaction of lattice vibrations (phonon wave-packets) with an asymmetric kink soliton initially at rest. We employ the $\phi^6$ model in one space and one time dimensions for various lattice spacings and consider two different discretization prescriptions for the field potential that do not generate Peierls-Nabarro potentials, i.e. the kink can be placed anywhere along the lattice beyond discrete translational invariance. Since the $\phi^6$ model kink is neither symmetric nor anti-symmetric under spatial reflections we simulate the cases where the wave-packet approaches the kink from negative or positive spatial infinity. We extract the energy transmission and reflection coefficients as functions of the central frequency of the phonon wave-packet for the different lattice spacings. For large lattice spacings the wave-packet is always fully reflected while for smaller spacing the amount of reflection and transmission depends on the central frequency. We also identify scenarios in which the target kink acquires a non-zero velocity from its interaction with the wave-packet.

An appropriate Lagrangian is considered for a system comprising a moving nanoparticle in a semi-infinite space, and the electromagnetic and matter fields are quantized. Through an analysis of the absorbed power radiation, it is demonstrated that the quantum friction experienced by high-velocity nanoparticles can be identified as a dissipative term in the radiation power of the nanoparticle. The absorbed power radiation for a moving nanoparticle is derived and compared with that of a static one. By considering two different temperature scenarios, it is explicitly shown that the absorbed power radiation for a moving nanoparticle always contains a negative term in its power spectrum, which can be attributed to the power lost due to non-contact quantum friction.

The two major effects observed in collisions of the continuum phi(4) kinks are (i) the existence of critical collision velocity above which the kinks always emerge from the collision and (ii) the existence of the escape windows for multi-bounce collisions with the velocity below the critical one, associated with the energy exchange between the kink's internal and translational modes. The potential merger (for sufficiently low collision speeds) of the kink and antikink produces a bion with oscillation frequency (D B , which constantly radiates energy, since its higher harmonics are always within the phonon spectrum. Similar effects have been observed in the discrete phi(4) kink-antikink collisions for relatively weak discreteness. Here we analyze kinks colliding with their mirror image antikinks in the regime of strong discreteness considering an exceptional discretization of the phi(4) field equation where the static Peierls-Nabarro potential is precisely zero and the not-too-fast kinks can propagate practically radiating no energy. Several new effects are observed in this case, originating from the fact that the phonon band width is small for strongly discrete lattices and for even higher discreteness an inversion of the phonon spectrum takes place with the short waves becoming low-frequency waves. When the phonon band is narrow, not a bion but a discrete breather with frequency omega(DB) and all higher harmonics outside the phonon band is formed. When the phonon spectrum is inverted, the kink and antikink become mutually repulsive solitary waves with oscillatory tails, and their collision is possible only for velocities above a threshold value sufficient to overcome their repulsion. (C) 2020 Elsevier Ltd. All rights reserved.

In this paper, we consider the interaction of small amplitude waves (phonons) with standing discrete breather (DB) in the one-dimensional chain of harmonically coupled particles interacting with the anharmonic one-site potential, which can be of hard-type or soft-type anharmonicity. The coefficients of phonon reflection and transmission are calculated numerically. It is found that for the case of hard-type anharmonicity (soft-type anharmonicity) DBs are more transparent for short-wavelength (long-wavelength) phonon waves, while they efficiently reflect long-wavelength (short-wavelength) phonons. In thermal equilibrium, when all phonons have equal energy density, it is found that for the same width of the transparency window, DB transmits less energy in the case of the hard-type anharmonicity. This is so because, in this case, DB reflects long-wavelength phonons, which have larger group velocity and hence greater contribution to the net energy flux through the DB. In this sense, DBs more efficiently suppress thermal conductivity in the chain with hard-type anharmonicity. Our results contribute to a better understanding of the role of discrete breathers in the heat flow in nonlinear chains.

We study the kink-antikink scattering within the double sine-Gordon model. In the numerical simulations we found a critical value vcr of the initial velocity vin, which separates two different scenarios: at vin < vcr the kinks capture each other and form a bound state, while at vin > vcr the kinks pass through each other and escape to infinities. We obtain non-monotonous dependence of vcr on the model parameter R. Besides that, at some initial velocities below vcr we observe formation and interaction of the so-called oscillons (new phenomenon), as well as escape windows (well-known phenomenon).

A collective coordinate system in (2+1) dimensional space-time is proposed to study the soliton-like solutions of the model. Scattering of the solutions from potential obstructions is investigated using these collective coordinates. Most of the features of the soliton-potential interaction are derived analytically using the proposed collective coordinate system while numerical simulation of the model can be done with some difficulties. A model for adding the potential obstructions to the equation of motion is presented too.

In our recent study the maximal values of kinetic and potential energy densities that can be achieved in the collisions of N slow kinks in the sine-Gordon model were calculated analytically (for N = 1, 2, and 3) and numerically (for 4 ≤ N ≤ 7). However, for many physical applications it is important to know not only the total potential energy density but also its two components (the on-site potential energy density and the elastic strain energy density) as well as the extreme values of the elastic strain, tensile (positive) and compressive (negative). In the present study we give (i) the two components of the potential energy density and (ii) the extreme values of elastic strain. Our results suggest that in multi-soliton collisions the main contribution to the potential energy density comes from the elastic strain, but not from the on-site potential. It is also found that tensile strain is usually larger than compressive strain in the core of multi-soliton collision.

We study the scattering of kink and antikink of the double sine-Gordon model. There is a critical value of the initial velocity v_cr of the colliding kinks, which separates different regimes of the collision. At v_in>v_cr we observe kinks reflection, while at v_in<v_cr their interaction is complicated with capture and escape windows. We obtain the dependence of v_cr on the parameter of the model. This dependence possesses a series of local maxima, which has not been reported by other authors. At some initial velocities below the critical value we observe a new phenomenon – the escape of two oscillons in the final state. Besides that, at v_in<v_cr we found the initial kinks’ velocities at which the oscillons do not escape, and the final configuration looks like a bound state of two oscillons.

Creation of solitons as kink–antikink pairs from particles is investigated, in the ϕ4 model. Particle-like states are simulated by two widely separated identical wave trains which are propagated toward collision point from both sides in a trivial background. The maximal energy density that can be achieved in the collisions of the particle-like wave trains is investigated numerically for different wave train parameters. Maximum energy and number of kink–antikink pairs created after the collision is calculated and the relation between them are studied. It is shown numerically that, if the number of created kink–antikink pairs are N, the maximal energy density should be at least equal to N2∕2.

In this study, Mn-ferrite has been prepared with nominal formula of MnFe2O4, using the dry conventional ceramic method. The raw materials were Mobarakeh steel company modified domestic iron oxide and Merk manganese oxide. XRD patterns of the prepared samples show that they are single phase. Magnetic measurements have been performed on the toroidal samples sintered in different temperatures, using a hystograph unit MPG100D model. The results of measurements show that optimum formation pressures to obtain maximum relative magnetic permeability and hystersis. We report here the observation of the Mn 55 nuclear magnetic resonance associated with the Mn2 + ion in the ferromagnetic spinel MnFe 2 O 4 also.

Interaction of solitons of noncommutative sine-Gordon model with potentials is studied by including a potential through one of the soliton parameters. The bahaviour of non commutative solitons during the interaction are compared with commutative solitons and the differences are explained.