Narrow Results

Our universe might be a domain wall or kink carrying localized standard model fields embedded in a 4 + 1-dimensional space. I report on some initial studies of the cosmology of such a model, focusing on the relatively simple de Sitter (dS) and Anti-de Sitter (AdS) cases for the effective 3 + 1-dimensional FRW metric. Fermion localization to the AdS₄ and dS₄ domain walls is briefly discussed.

We propose a framework to construct “Domain-Wall Standard Model” in a non-compact 5-dimensional spacetime, where all the Standard Model (SM) fields are localized in certain domains of the 5th dimension and the SM is realized as a 4-dimensional effective theory without any compactification for the 5th dimension. In this context, we investigate the collider phenomenology of the Kaluza–Klein (KK) modes of the SM gauge bosons and the current constraints from the search for a new gauge boson resonance at the Large Hadron Collider Run-2. The couplings of the SM fermions with the KK-mode gauge bosons depend on the configuration of the SM fermions in the 5-dimensional bulk. This “geometry” of the model can be tested at the future Large Hadron Collider experiment, once a KK-mode of the SM gauge boson is discovered.

The Casimir forces on two parallel plates in conformally flat de Sitter background due to conformally coupled massless scalar field satisfying mixed boundary conditions on the plates is investigated. In the general case of mixed boundary conditions formulae are derived for the vacuum expectation values of the energy–momentum tensor and vacuum forces acting on boundaries. Different cosmological constants are assumed for the space between and outside of the plates to have general results applicable to the case of domain wall formations in the early universe.

A class of domain-wall-like solutions of the Skyrme model is obtained analytically. They are described by the tangent hyperbolic function, which is a special limit of the Weierstrass ℘ function. The behavior of one of the two terms in the static energy density is like that of a domain wall. The other term in the static energy density does not vanish but becomes constant at the points far apart from the wall.

Domain walls in gauge theory with non-Abelian flavor symmetry possess normalizable Nambu-Goldstone zero modes associated with spontaneously broken non-Abelian flavor symmetry. We construct the moduli space metric as the effective field theory of walls. The Nambu-Goldstone modes spread between two domain walls and their rotation induces long-range repulsive force. We also construct a bound state of domain walls. This article is based on the work with M. Eto, M. Nitta, K. Ohashi and N. Sakai¹.

In this paper, we show that the supergravity theory which is dual to ABJM field theory can be consistently reduced to scalar-coupled AdS-Einstein gravity and then consider the reflection symmetric domain wall and its small fluctuation. It is also shown that this domain wall solution is none other than dimensional reduction of M2-brane configuration.

In this paper an attempt has been made to study the flat fractal Friedmann–Robertson–Walker model filled with domain walls. We have obtained the fractal equation of deceleration parameter and tension of the domain wall. It is observed that, while domain walls exist at early times, they disappear at late time. Finally, some physical parameters of the model are discussed using graphs.

Using a recently proposed new renormalization group method (tensor renormalization group), we analyze the Ising model on the two-dimensional square lattice. For the lowest-order approximation with two-domain wall states, it realizes the idea of coarse graining of domain walls. We write down explicit analytic renormalization transformation and prove that the picture of the coarse graining of the physical domain walls does hold for all physical renormalization group flows. We solve it to get the fixed point structure and obtain the critical exponents and the critical temperature. These results are very near to the exact values. We also briefly report the improvement using four-domain wall states.

The effect of interface misfit strain on the movement and tilt angles of the domain wall in ferroelectric thin film is investigated with a multicoupling finite element model. Since this theoretical model is developed based on the phase field method and is solved using the finite element method, it can effectively predict the electromechanical coupling behavior of materials that have complicated boundary conditions. The simulated results demonstrate that the position, tilt angles, strain gradient and energy density of the domain wall can be modulated by misfit compressive strain at the interface of ferroelectric nanostructures. A larger interface misfit compressive strain will lead to the movement of domain wall towards the direction which allows the $a$ domain to possess a larger volume. The difference of the tilt angles of domain walls on both sides of the $a$ domain becomes larger as the interface misfit strain increases, implying a transition of the shape of the $a$ domain from parallelogram to wedge.

Ferroelectric stripe domain structure and domain walls were investigated by vector PFM on epitaxial BiFeO₃ thin films. Measurements of topography of film versus distance between spikes, we identify the $109^{\circ }$ domain in the film, were supported by XRD and AFM characterization. $109^{\circ }$ domain can be switched under the electric field engendered by the biased PFM tip, and their controllable $109^{\circ }$ rotation can be maintained by electron injection by the PFM tip. These stripe domain walls are conductive, provide an opportunity to further study their new properties in high-density memory devices.

Starting from the classical equation of the motion of a domain wall in the ferromagnetic systems, the quantum energy levels of the wall and the corresponding eigenfunctions in the case of considering damping term are given by using the canonical quantization method and unitary transformation. The quantum fluctuations of displacement and momentum of the moving wall has also been given as well as the uncertain relation.

The response of an underdamped stochastic resonance (SR) with a new pining potential model of domain wall (DW) in ferromagnetic strips driven by additive Gaussian white noise to an additive weak harmonic forcing is investigated. We address that the new nonlinear system can be converted between bi-stable and mono-stable freely by tuning the system parameters. Analytical expressions of signal-to-noise ratio (SNR) of the bi-stable stage is obtained based on the linear response theory. In addition, another type of SR, which occurs when the system is mono-stable, is also reported with the intrinsic frequency derived analytically. The SR in mono-stable stage confirms to the typical physical resonance better with frequency-selection characteristic. Numerical simulation of both stages is carried out with outputs conforming to the theoretical derivation. Owing to the diversity of potential model, the new system possesses considerable merits for engineering applications.

We investigate gravitational properties of thin planar wall solutions of the Einstein's equations in the weak field approximation. We find the general metric solutions and discuss the behavior of a particle placed initially at rest to one side of the plane. Moreover we study the case of non-reflection-symmetric solutions.

Well known weakness of gravity in particle physics is an illusion caused by underestimation of the role of spin in gravity. Relativistic rotation is inseparable from spin, which for elementary particles is extremely high and exceeds mass on 20–22 orders (in units $c=G=m=\hslash =1$). Such a huge spin generates frame-dragging that distorts space much stronger than mass, and effective scale of gravitational interaction is shifted from Planck to Compton distances. We show that compatibility between gravity and quantum theory can be achieved without modifications of Einstein–Maxwell equations, by coupling to a supersymmetric Higgs model of symmetry breaking and forming a nonperturbative super-bag solution, which generates a gravity-free Compton zone necessary for consistent work of quantum theory. Super-bag is naturally upgraded to Wess–Zumino supersymmetric QED model, forming a bridge to perturbative formalism of conventional QED.

Based on density functional theory and nonequilibrium Green’s function method, we study the magnetic order and collinear/noncollinear spin transport of 180${}^{\circ }$ domain wall (DW) made by transition metal (TM)-doped Ni atomic chain. The results show that the TM doping reproduces characteristic features depending on the type of TM elements, the number of dopants and the initial magnetization distribution. In the collinear magnetization, which is obtained from the initial condition of abrupt DW, the two dopants show symmetric features while the single dopant presents a varying magnetic moment on the TM dopant when the number of 3d electrons of dopant increases. As the magnetization is noncollinear (spiral-like), the magnetization becomes complicated. For instance, the rotation sense of magnetization changes from clockwise to counter-clockwise for some TM dopants. In addition, the transmission of doped Ni chain shows two scattering mechanisms, i.e. electronic scattering due to quasi-bound state and due to the spin-flip scattering. Our results reported here provide considerable insights into the doping effect on magnetization and spin transport of atomic-scale DW.

We report on a new character of single domain wall (DW) of electrically-poled ferroelectric crystal which can modulate parametric processes via Cherenkov-type phase matching. Experimental result shows that the effective nonlinear polarization is confined in DW, and its phase velocity can be modulated when incident light is off the domain wall's direction. These effects lead to novel Cherenkov second harmonic generation (CSHG), and other modulated parametric process, such as Cherenkov sum frequency generation (CSFG).

We reveal a variety of nonlinear Cerenkov radiation (NCR) patterns that occur in a single photonic crystal modulated by domain walls, which manifest themselves as normal, degenerated, and anomalous-dispersion-like NCR type sum-frequency generation. The phase-matching geometries of the evolution of Cerenkov radiation varying with the dispersion relationship among the interaction waves are exploited, respectively.

Nanometer-scale movements of domain walls in uniaxial garnet films have been studied by means of micromagnetization measurements using miniature gold and semiconductor Hall probes. At helium temperatures the domain walls are found to move by discrete jumps, which we attribute to pinning on isolated defects, and we were able to measure local hysteresis loops associated with pinning on individual pinning centers. The temperature dependence of the coercive field of a single pinning center allowed us to evaluate the characteristic energy and characteristic volume of the pinning center.

The domain wall structure of ferroelectric/ paraelectric superlattices can be much more complex due to the influence of the superlattice stacking structure, the in-plane strain induced by the substrate and environmental temperature. In this study, we employed a phase field model to investigate the domain wall state of the SrTi${\mathrm{\text{O}}}_3$/BaTi${\mathrm{\text{O}}}_3$ superlattice structure. The domain wall thickness for the SrTi${\mathrm{\text{O}}}_3$/BaTi${\mathrm{\text{O}}}_3$ layer was measured using a hyperbolic function. Based on the simulation results, here, we show a domain wall state diagram to distinguish the hard and soft domain states. The polarization profiles across hard/ soft domain walls were illustrated and analyzed. Our simulation results offer a useful concept for the control of the domain wall state in the ferroelectric superlattice.

We calculate a superconformal index of the half-BPS duality domain wall inserted at the great S² of S³ in SU(2) super Yang-Mills theory on S¹ × S³.