Backlund transformations for Burgers Equation via localization of residual symmetries

In this paper, we obtained the non-local residual symmetry related to truncated Painlev\'e expansion of Burgers equation. In order to localize the residual symmetry, we introduced new variables to prolong the original Burgers equation into a new system. By using Lie's first theorem, we got the finite transformation for the localized residual symmetry. More importantly, we also localized the linear superposition of multiple residual symmetries to find the corresponding finite transformations. It is interesting to find that the nth Backlund transformation for Burgers equation can be expressed by determinants in a compact way

New interaction solutions of Kadomtsev-Petviashvili equation

The residual symmetry coming from truncated Painleve expansion of KP equation is nonlocal, which is localized in this paper by introducing multiple new dependent variables. By using the standard Lie group approach, the symmetry reduction solutions for KP equation is obtained based on the general form of Lie point symmetry for the prolonged system. In this way, the interaction solutions between solitons and background waves is obtained, which is hard to study by other traditional methods

New symmetry reductions related with the residual symmetry of Boussinesq equation

The Backlund transformation related symmetry is nonlocal, which is hardly to apply in constructing solutions for nonlinear equations. In this paper, we first localize nonlocal residual symmetry to Lie point symmetry by introducing multiple new variables and obtain new Baaklund transformation. Then, by solving out the general form of localized the residual symmetry, we reduce the enlarged system by classical symmetry approach and obtain the corresponding reduction solutions as well as related reduction equations. The localization procedure provides a new way to investigate interaction solutions between different waves

Residual Symmetry Reductions and Interaction Solutions of (2+1)-Dimensional Burgers Equation

The (2+1)-dimensional Burgers equation has been investigated first from prospective of symmetry by localizing the nonlocal residual symmetries and then studied by a simple generalized tanh expansion method. New symmetry reduction solutions has been obtained by using the standard Lie point symmetry group approach. A new B\"{a}klund transformation for Burgers equation has been given with the generalized tanh expansion method . From this BT, interactive solutions among different nonlinear excitations which is hard to obtain by other methods has also been obtained easily

Pseudo-Spin, Real-Spin and Spin Polarization of Photo-emitted Electrons

In this work, we discuss the connections between pseudo spin, real spin of electrons in material and spin polarization of photo-emitted electrons out of material. By investigating these three spin textures for Bi$_2$Se$_3$ and SmB$_6$ compounds, we find that the spin orientation of photo-electrons for SmB$_6$ has different correspondence to pseudo spin and real spin compare to Bi$_2$Se$_3$, due to the different symmetry properties of the photo-emission matrix between initial and final states. We calculate the spin polarization and circular dichroism spectra of photo-emitted electrons for both compounds, which can be detected by spin-resolved and circular dichroism angle resolved photo-emission spectroscopy experiment.Comment: 9 pages, 11 figure

Coherent-feedback-induced photon blockade and optical bistability by an optomechanical controller

It is well-known that some nonlinear phenomena such as strong photon blockade are hard to be observed in optomechanical system with current experimental technology. Here, we present a coherent feedback control strategy in which a linear cavity is coherently controlled by an optomechanical controller in a feedback manner. The coherent feedback loop transfers and enhances quantum nonlinearity from the controller to the controlled cavity, which makes it possible to observe strong nonlinear effects in either linear cavity or optomechanical cavity. More interestingly, we find that the strong photon blockade under single-photon optomechanical weak coupling condition could be observed in the quantum regime. Additionally, the coherent feedback loop leads to two-photon and multiphoton tunnelings for the controlled linear cavity, which are also typical quantum nonlinear phenomenon. We hope that our work can give new perspectives in engineering nonlinear quantum phenomena.Comment: 12 pages, 11 figure

Catalyst type of interactions between dark energy and dark matter

In this paper, we focus on three specific interactions of dark sector in the existence of baryonic matter and radiation. First, we attempt to assume baryonic matter and radiation can affect the conversion between dark energy and dark matter like the way catalyst influences the conversion rate of two materials in some reversible chemical reactions. Then we present phase space analysis for every special interaction model. Finally, for every case, we obtain a stable attractor solution that can alleviate the coincidence problem.Comment: 8 pages,3 table

Model Hamiltonian for topological Kondo insulator SmB6

Starting from the kp method in combination with first-principles calculations, we systematically derive the effective Hamiltonians that capture the low energy band structures of recently discovered topological Kondo insulator SmB6. Using these effective Hamiltonians we can obtain both the energy dispersion and the spin texture of the topological surface states, which can be detected by further experiments.Comment: 6 pages, 4 figure

Quantum anomalous Hall effect and related topological electronic states

Over a long period of exploration, the successful observation of quantized version of anomalous Hall effect (AHE) in thin film of magnetically-doped topological insulator completed a quantum Hall trio---quantum Hall effect (QHE), quantum spin Hall effect (QSHE), and quantum anomalous Hall effect (QAHE). On the theoretical front, it was understood that intrinsic AHE is related to Berry curvature and U(1) gauge field in momentum space. This understanding established connection between the QAHE and the topological properties of electronic structures characterized by the Chern number. With the time reversal symmetry broken by magnetization, a QAHE system carries dissipationless charge current at edges, similar to the QHE where an external magnetic field is necessary. The QAHE and corresponding Chern insulators are also closely related to other topological electronic states, such as topological insulators and topological semimetals, which have been extensively studied recently and have been known to exist in various compounds. First-principles electronic structure calculations play important roles not only for the understanding of fundamental physics in this field, but also towards the prediction and realization of realistic compounds. In this article, a theoretical review on the Berry phase mechanism and related topological electronic states in terms of various topological invariants will be given with focus on the QAHE and Chern insulators. We will introduce the Wilson loop method and the band inversion mechanism for the selection and design of topological materials, and discuss the predictive power of first-principles calculations. Finally, remaining issues, challenges and possible applications for future investigations in the field will be addressed.Comment: Review Article published in , and update

Topological Nodal Line Semimetal and Dirac Semimetal State in Antiperovskite Cu3_3PdN

Based on first-principles calculation and effective model analysis, we propose that the cubic antiperovskite material Cu$_3$PdN can host a three-dimensional (3D) topological nodal line semimetal state when spin-orbit coupling (SOC) is ignored, which is protected by coexistence of time-reversal and inversion symmetry. There are three nodal line circles in total due to the cubic symmetry. "Drumhead"-like surface flat bands are also derived. When SOC is included, each nodal line evolves into a pair of stable 3D Dirac points as protected by C$_4$ crystal symmetry. This is remarkably distinguished from the Dirac semimetals known so far, such as Na$_3$Bi and Cd$_3$As$_2$, both having only one pair of Dirac points. Once C$_4$ symmetry is broken, the Dirac points are gapped and the system becomes a strong topological insulator with (1;111) Z$_2$ indices.Comment: 6 pages, 4 figure