In this work we study kink-antikink and antikink-kink collisions in hyperbolic models of fourth and sixth order. We compared the patterns of scattering with known results from polynomial models of the same order. The hyperbolic models considered here tend to the polynomial $ϕ^4$ and $ϕ^6$ models in the limit of small values of the scalar field. We show that kinks and antikinks that interact hyperbolically with fourth order differ sensibly from those governed by the polynomial $ϕ^4$ model. The increasing of the order of interaction to the sixth order shows that the hyperbolic and polynomial models give intricate structures of scattering that differ only slightly. The dependence on the order of interaction are related to some characteristics of the models such as the potential of perturbations and the number of vibrational modes.
In this work we examine kink-antikink collisions in two distinct hyperbolic models. The models depend on a deformation parameter, which controls two main characteristics of the potential with two degenerate minima: the height of the barrier and the values of the minima. In particular, the rest mass of the kinks decreases monotonically as the deformation parameter increases, and we identify the appearance of a gradual suppression of two bounce windows in the kink scattering and the production of long lived oscillons. The two effects are reported in connection to the presence of more than one vi…
At leading order, there are three inelastic scattering processes beginning with a quantum kink and a fundamental meson. Meson multiplication, in which the final state is a kink and two mesons, was treated recently. In this note we treat the other two, (anti)-Stokes scattering, in which the kink's shape mode is (de-)excited and the final state contains one meson. In the case of a general scalar kink, we find analytic formulas for the forward and backward scattering amplitudes and probabilities as functions of the momentum of the incident meson. The general results are then specialized to the ki…
In this work we consider kink-antikink and antikink-kink collisions in a modified $ϕ^4$ model with a false vacuum characterized by a dimensionless parameter $ε$. The usual $ϕ^4$ model is recovered for $ε=0$. We investigate the $ε<<1$ regime where the kink in the presence of false vacuum can be understood as a small deformation of the standard kink for the $ϕ^4$ model. We show that the attractive interaction between the kink-antikink pair leads to a rich scattering pattern, in some cases delaying considerably the false vacuum decay.
We study some properties of kink solutions of the model with non-polynomial potential obtained by deforming the well-known $φ^6$ field model. We consider the excitation spectrum of the kink. We also discuss the properties of the `kink+antikink' system as a whole that are not inherent to a solitary kink or antikink.
The role played by a Lorentz-violating term on the outcomes of kink scattering in the $ϕ^6$ model is investigated by using the Fourier spectral method. Impacts of the Lorentz-violating term on the critical velocities, the location of two-bounce windows, and the maximal values of various types of energy densities are analyzed. Some novel features of kink-antikink collisions are discussed. The interactions between three and four kinks are also considered.
We calculate the leading quantum corrections to the meson form factors of nonrelativistic kinks, at momentum transfer much higher than the meson mass. We consider general scalar theories which need not be integrable. Our approach is much simpler than previous approaches, avoiding any need for counterterms, ordering ambiguities and nonlinear canonical transformations at any order in perturbation theory.
Two hyperbolic-deformed field theoretic models are discussed. In both of them, due to the effect of specific deformation function on the well known $φ^4$ and $φ^6$ models, their internal structure may change significantly. Unlike the $φ^4$ kinks solutions, which has only one internal mode in addition to its translational mode, the kinks of the hyperbolic-deformed $φ^4$ model can have several internal modes. Moreover, the deformation on the $φ^6$ model has other interesting features, because the kinks of the $φ^6$ model have only a zero mode and the deformation may cause the appearance of inter…
In this paper, we investigate the scattering of two $ϕ^6$ kinks and derive the real dynamics by solving the appropriate field equation numerically employing a Runga-Kutta method. We also use a collective coordinate approximation to find approximate dynamics, with the objective being to compare the approximate motion to the real dynamics in order to test the validity of this kind of approximation, which is used extensively in the study of solitons.
Elastic Kink-Meson Scattering in the $Φ^4$ Double-Well Model
Alikhanian National Laboratory (Yerevan Physics Institute)（阿利哈尼扬国家实验室（叶里温物理研究所））；School of Physics, Xi’an Jiaotong University（西安交通大学物理学院）；Institute of Modern Physics（现代物理研究所）；University of the Chinese Academy of Sciences（中国科学院大学）
We study the scattering properties of Sine Gordon kinks on obstructions in the form of finite size potential `wells'. We model this by making the coefficient of the $\cos(ϕ)-1$ term in the Lagrangian position dependent. We show that when the kinks find themselves in the well they radiate and then interact with this radiation. As a result of this energy loss the kinks become trapped for small velocities while at higher velocities they are transmitted with a loss of energy. However, the interaction with the radiation can produce `unexpected' reflections by the well. We present two simple models …
Kink-antikink scattering in the $ϕ^4$ model is investigated in the limit when the static inter-soliton force vanishes. We observe the formation of spectral walls and, further, identify a new phenomenon, the vacuum wall, whose existence gives rise to a bouncing structure for the annihilating solitons. Furthermore, we discover higher order spectral walls, i.e., spectral walls which form when higher harmonics enter the continuous spectrum. These higher order spectral walls not only deform the soliton trajectories, they also can be observed easily as very intense radiation bursts.
In this work we investigate several models described by a single real scalar field with non-polynomial interactions, constructed to support topological solutions. We do this using the deformation procedure to introduce a function which allows to construct two distinct families of hyperbolic potentials, controlled by three distinct parameters, in the standard formalism. In this way, the procedure allows us to get analytical solutions, and then investigate the energy density, linear stability and zero mode. We move on and introduce a non-standard formalism to obtain compact solutions, analytical…
We investigate the role that quasinormal modes can play in kink-antikink collisions, via an example based on a perturbation of the $ϕ^4$ model. We find that narrow quasinormal modes can store energy during collision processes and return it back to the translational degrees of freedom. Quasinormal modes also decay, which leads to energy leakage, causing a closing of resonance windows and an increase of the critical velocity. We observe similar phenomena in an effective model, a small modification of the collective-coordinate approach to the $ϕ^4$ model.
In this paper the scattering between the non-topological kinks arising in a family of two-component scalar field theory models is analyzed. A winding charge is carried by these defects. As a consequence, two different classes of kink scattering processes emerge: (1) collisions between kinks that carry the same winding number and (2) scattering events between kinks with opposite winding number. The variety of scattering channels is very rich and it strongly depends on the collision velocity and the model parameter. For the first type of events, four distinct scattering channels are found: \text…
In this work we consider a model where the potential has two topological sectors connecting three adjacent minima, as occurs with the $ϕ^6$ model. In each topological sector, the potential is symmetric around the local maximum. For $ϕ>0$ there is a linear map between the model and the $λϕ^4$ model. For $ϕ<0$ the potential is reflected. Linear stability analysis of kink and antikink lead to discrete and continuum modes related by a linear coordinate transformation to those known analytically for the $λϕ^4$ model. Fixing one topological sector, the structure of antikink-kink scattering is relate…
In this paper we examine the scattering processes among the members of a rich family of kinks which arise in a (1+1)-dimensional relativistic two scalar field theory. These kinks carry two different topological charges that determine the mutual interactions between the basic energy lumps (extended particles) described by these topological defects. Processes like topological charge exchange, kink-antikink bound state formation or kink repulsion emerge depending on the charges of the scattered particles. Two-bounce resonant windows have been found in the antikink-kink scattering processes, but n…
We use a recently constructed linearized soliton sector perturbation theory to calculate the form factors relevant to the elastic scattering of ultrarelativistic mesons off of nonrelativistic kinks. Both localized kink wave packets and also delocalized momentum eigenstate kinks are considered. In the delocalized case, the leading term is just the classical kink solution, as was found by Goldstone and Jackiw. The leading delocalized quantum correction agrees with that found by Gervais, Jevicki and Sakita in the $ϕ^4$ model and Weisz in the Sine-Gordon model. In the case of localized kink wave p…
In this paper, kink scattering in the dimensional reduction of the bosonic sector of a one-parameter family of generalized Wess-Zumino models with three vacuum points is discussed. The value of the model parameter determines the specific location of the vacua. The influence of the vacuum arrangements (evolving from three collinear vacua to three vacua placed at the vertices of an equilateral triangle) on the kink scattering is investigated. Two different regimes can be distinguished: in the first one, two symmetric BPS kinks/antikinks arise whereas in the second one a new different BPS kink/an…
In this paper kink scattering processes are investigated in the Montonen-Sarker-Trullinger-Bishop model. The MSTB model is in fact a one-parametric family of relativistic scalar field theories living in a one-time one-space Minkowski space-time which encompasses two coupled scalar fields. Between the static solutions of the model two kinds of topological kinks are distinguished in a precise range of the family parameter. In that regime there exists one unstable kink exhibiting only one non-null component of the scalar field. Another type of topological kink solutions, stable in this case, incl…
The scattering of Dirac fermions on the sine-Gordon kink is studied both analytically and numerically. To achieve invariance with respect to a discrete symmetry, the sine-Gordon model is treated as a nonlinear $σ$-model with a circular target space that interacts with fermionic isodublets through the Yukawa interaction. It is shown that the diagonal and antidiagonal parts of the fermionic wave function interact independently with the external field of the sine-Gordon kink. The wave functions of the fermionic scattering states are expressed in terms of the Heun functions. General expressions fo…
Interaction of asymmetric $ϕ^6$ kinks with a spatially localized $\mathcal{PT}$-symmetric perturbation is investigated numerically. It has been shown that when the kink (antikink) hits the defect from the gain side, a final velocity of the kink decreases (increases), while for the kink and antikink coming from the opposite direction their final velocities remain unchanged. It is also found that when the kink interacts with the defect from the gain side multiple pair of the kink-antikink are formed from small amplitude waves (phonons) in the final states depending on the initial velocity of the…
In this paper, we numerically study the scattering of kinks in the noncanonical sine-Gordon model using Fourier spectral methods. The model depends on two free parameters, which control the localized inner structure in the energy density and the characteristics of the scattering potential. It has been conjectured that the kink solutions in the noncanonical model possess inner structures in their energy density, and the presence of these yields bound states and resonance structures for some relative velocities between the kink and the antikink. In the numerical study, we observed that the class…
We consider the (1+1)-dimensional Lorentz-symmetric field-theoretic model with logarithmic potential having a Mexican-hat form with two local minima similar to that of the quartic Higgs potential in conventional electroweak theory with spontaneous symmetry breaking and mass generation. We demonstrate that this model allows topological solutions -- kinks. We analyze the kink excitation spectrum, and show that it does not contain any vibrational modes. We also study the scattering dynamics of kinks for a wide range of initial velocities. The critical value of the initial velocity occurs in kink-…
Recently it was shown that kink baryons and kink-antikink scattering in the massless Gross-Neveu model are closely related to one- and two-soliton solutions of the sinh-Gordon equation. Here we generalize these findings to the case of n kinks and antikinks. Using the known n soliton solution of the sinh-Gordon equation, we solve the general n kink-antikink scattering problem in the large N Gross-Neveu model analytically, mapping the time-dependent Hartree-Fock approach onto inverse scattering theory.
The collective coordinates approximation for the kink/anti-kink scattering in the $1+1$ dimensional $ϕ^4$ model is considered and we discuss how the results found in the current literature on the topic can be improved by giving the analytical expression for the lagrangian in the space of parameters. A comprehensive discussion of the role of the collective coordinates approximation in this particular situation is given for completeness.
We study numerically the kink-fermion interactions in a 1+1 dimensional toy model, which describes sine-Gordon kinks coupled to the massless Dirac fermions with backreaction. We show that the spectrum of fermionic modes strongly depends on the choice of the coupling, in particular, there are no localized modes for a minimal Yukawa coupling. We analyze the scattering of the fermionic packet by the kink. We demonstrate that the outcome of the collision dynamically depends on the phase of the incoming fermion packet, it results in alternating regimes of positive and negative acceleration of the k…
In this paper the scattering between a wobbling kink and a wobbling antikink in the standard $ϕ^4$ model is numerically investigated. The dependence of the final velocities, wobbling amplitudes and frequencies of the scattered kinks on the collision velocity and on the initial wobbling amplitude is discussed. The fractal structure becomes more intricate due to the emergence of new resonance windows and the splitting of those arising in the non-excited kink scattering. Outside this phase the final wobbling amplitude exhibits a linear dependence of the collision velocity whereas the final freque…
Scattering of kinks in Frankensteinian potentials: Kinks as bubbles of exotic mass and phase transitions in oscillon production
Institute of Physics, Silesian University in Opava（奥帕瓦西里西亚大学物理研究所）；Research Centre for Theoretical Physics and Astrophysics, Institute of Physics, Silesian University in Opava（奥帕瓦西里西亚大学物理研究所理论物理与天体物理研究中心）
The asymmetric scattering between wobblers and kinks in the standard $ϕ^4$ model is numerically investigated in two different scenarios. First, the collision between wobblers with opposite phase is analyzed. Here, a destructive interference between the shape modes of the colliding wobblers takes place at the impact time. The second scenario involves the scattering between a wobbler and an (unexcited) kink. In this case the energy transfer from the wobbler to the kink can be examined. The dependence of the final velocities and wobbling amplitudes of the scattered wobblers on the collision veloc…
In this paper the kink scattering in a two-component scalar field theory model in (1+1)-Minkowskian space-time is addressed. The potential term $U(ϕ_1,ϕ_2)$ is given by a polynomial of fourth degree in the first field component and of sixth degree in the second one. The novel characteristic of this model is that the kink variety describes two different types of extended particles. These particles are characterized by its topological charge but also by a new feature determined by a discrete charge $Λ=0,\pm 1$. For this reason, the kink scattering involves a very rich variety of processes, which…
In this work we consider model of asymmetric kinks, where the behavior of the solution in one side is different from the other side. Also, the models depend of an integer $n$ and, with the increase of $n$, the constructed kink assumes a hybrid character: a compactlike profile on one side and a kinklike profile on the other side. We investigate numerically the kink-antikink and antikink-kink dynamics, with the aim to understand the effect of the transition of the usual kink to the semi-compacton structure. The kink-antikink process shows the formation of one-bounce windows for small values of $…
We determine the excitations and $S$ matrix of an integrable isotropic antiferromagnetic quantum spin chain of alternating spin 1/2 and spin 1. There are two types of gapless one-particle excitations: the usual spin 1/2 (``spinor'') kink, and a new spin 0 (``scalar'') kink. Remarkably, the scalar-spinor scattering is nontrivial, yet the spinor-spinor scattering is the same as if the scalar kinks were absent. Moreover, there is no scalar-scalar scattering.
We study kink-antikink scattering in the sine-Gordon model in the presence of interactions with an additional scalar field, $ψ$, that is in its quantum vacuum. In contrast to the classical scattering, now there is quantum radiation of $ψ$ quanta and the kink-antikink may form bound states that resemble breathers of the sine-Gordon model. We quantify the rate of radiation and map the parameters for which bound states are formed. Even these bound states radiate and decay, and eventually there is a transition into long-lived oscillons.
We study the scattering of the $φ^8$ kinks off each other, namely, we consider those $φ^8$ kinks that have power-law asymptotics. The slow power-law fall-off leads to a long-range interaction between the kink and the antikink. We investigate how the scattering scenarios depend on the initial velocities of the colliding kinks. In particular, we observe the `escape windows' -- the escape of the kinks after two or more collisions, explained by the resonant energy exchange between the translational and vibrational modes. In order to elucidate this phenomenon, we also analyze the excitation spectra…
We show that thick spectral walls exist in antikink-kink collisions in the $ϕ^6$ model. In this model, they are triggered by the so-called $delocalized$ $modes$ which do not exist in the single-soliton sector but emerge in antikink-kink ($\bar{K}K$) collisions. Therefore, spectral walls are a rather common phenomenon that should occur in many solitonic collisions involving non-symmetric kinks as, e.g., in the $ϕ^8$ or higher power models.
We study the scattering of the $φ^8$ kinks with power-law asymptotics. We found two critical values of the initial velocity, $v_{cr}^{(1)}$ and $v_{cr}^{(2)}$, which separate different regimes of the kink-antikink collision. At the initial velocities $v_{in}< v_{cr}^{(1)}$ kinks can not collide due to repulsive force between them. At $v_{in}>v_{cr}^{(2)}$ the kinks escape to spatial infinities after one collision. In the range $v_{cr}^{(1)}\le v_{in}\le v_{cr}^{(2)}$ we observed kinks capture and formation of their bound state. Besides that, at these initial velocities we found resonance pheno…
We consider the S-matrix bootstrap of four dimensional scattering amplitudes with $O(3)$ symmetry and no bound-states. We explore the allowed space of scattering lengths which parametrize the interaction strength at threshold of the various scattering channels. Next we consider an application of this formalism to pion physics. A signature of pions is that they are derivatively coupled leading to (chiral) zeros in their scattering amplitudes. In this work we explore the multi-dimensional space of chiral zeros positions, scattering length values and resonance mass values. Interestingly, we encou…
We study a model described by a single real scalar field in the two-dimensional space-time. The model is specified by a potential which is non-polynomial and supports analytical kink-like solutions that are similar to the standard kink-like solutions that appear in the $φ^4$ model when it develops spontaneous symmetry breaking. We investigate the kink-antikink scattering problem in the non-polynomial model numerically and highlight some specific features, which are not present in the standard case.
We study collisions of two, three, and four kinks of the double sine-Gordon model. The initial conditions are taken in a special form in order to provide collision of all kinks in one point. We obtain dependences of the maximal energy densities on the model parameter. We also analyze the final states observed in these collisions.
We investigate the scattering of fermions off domain walls at the electroweak phase transition in presence of a magnetic field. We consider both the bubble wall and the kink domain wall. We derive and solve the Dirac equation for fermions with momentum perpendicular to the walls, and compute the transmission and reflection coefficients. In the case of kink domain wall, we briefly discuss the zero mode solutions localized on the wall. The possibile role of the magnetic field for the electroweak baryogenesis is also discussed.
Ooguri and Vafa have shown that the open N=2 string corresponds to self-dual Yang-Mills (SDYM) and also that, in perturbation theory, it has has a vanishing four particle scattering amplitude. We discuss how the dynamics of the three particle scattering implies that on shell states can only scatter if their momenta lie in the same self-dual plane and then investigate classical SDYM with the aim of comparing exact solutions with the tree level perturbation theory predictions. In particular for the gauge group SL(2,C) with a plane wave Hirota ansatz SDYM reduces to a complicated set of algebraic…
For kink-antikink scattering within the ϕ^4 non--linear field theory in one space and one time dimension resonance type configurations emerge when the relative velocity between kink and antikink falls below a critical value. It has been conjectured that the vibrational excitation of the kink would be the source for these resonances because (simplified) collective coordinate calculations, that emphasized on this excitation, qualitatively reproduced those resonances. Surprisingly a numerical study in the ϕ^6 field theory also exhibited such resonances even though it does not contain the vibratio…
In a (1+1)-dimensional scalar quantum field theory, we calculate the leading-order probability of meson multiplication, which is the inelastic scattering process: kink + meson $\rightarrow$ kink + 2 mesons. We also calculate the differential probability with respect to the final meson momenta and the probability that one or two of the final mesons recoils back towards the source. In the ultrarelativistic limit of the initial meson, the total probability tends to a constant, which we calculate analytically in the $ϕ^4$ model. At this order the meson sector conserves energy on its own, while the…
