Momentum space topology of fermion zero modes brane

We discuss fermion zero modes within the 3+1 brane, i.e., the domain wall between the two vacua in 4+1 spacetime. We do not assume relativistic invariance in 4+1 spacetime or any special form of the 4+1 action. The only input is that the fermions in bulk are fully gapped and are described by a nontrivial momentum-space topology. Then the 3+1 wall between such vacua contains chiral 3+1 fermions. The bosonic collective modes in the wall form the gauge and gravitational fields. In principle, this universality class of fermionic vacua can contain all the ingredients of the Standard Model and gravity.     

Concept of polarity of free radicals in reactions of addition to olefins

The concept of polarity (nucleo- and electrophilicity) of free radicals in processes of addition to unsaturated substrates was developed within the framework of the method of qualitative potential energy surfaces on the basis of an analysis of the interaction of diabatic surfaces for reactions of free-radical addition to olefins. A formulation is given for the concept of the polarity (philicity) of the attacking free radical; the theoretical index of philicity and the criterion of polarity of the radicals are proposed; the concept of ambiphilicity of a radical is introduced. The chemical aspects of the philicity of free radicals — the influence of a change in it on the formation and height of the activation barrier of the reaction and the strength of the bond formed — are discussed. A parallel formulation of the concept of polarity of radicals in terms of boundary orbital interactions in the free-radical-unsaturated substrate system is given.Translated from Teoreticheskaya i Éxperimental'naya Khimiya, Vol. 22, No. 5, pp. 562–571, September–October, 1986.     

On the chiral magnetic effect in Weyl superfluid <Superscript>3</Superscript>He-A

In the theory of the chiral anomaly in relativistic quantum field theories (RQFTs), some results depend on a regularization scheme at ultraviolet. In the chiral superfluid ³He-A, which contains two Weyl points and also experiences the effects of chiral anomaly, the “trans-Planckian” physics is known and the results can be obtained without regularization. We discuss this on example of the chiral magnetic effect (CME), which has been observed in ³He-A in the 1990s [1]. There are two forms of the contribution of the CME to the Chern–Simons term in free energy, perturbative and non-perturbative. The perturbative term comes from the fermions living in the vicinity of the Weyl point, where the fermions are “relativistic” and obey the Weyl equation. The non-perturbative term originates from the deep vacuum, being determined by the separation of the two Weyl points in momentum space. Both terms are obtained using the Adler–Bell–Jackiw equation for chiral anomaly, and both agree with the results of the microscopic calculations in the “trans-Planckian” region. Existence of the two nonequivalent forms of the Chern–Simons term demonstrates that the results obtained within the RQFT depend on the specific properties of the underlying quantum vacuum and may reflect different physical phenomena in the same vacuum.     

Emergent Horava gravity in graphene

First of all, we reconsider the tight-binding model of monolayer graphene, in which the variations of the hopping parameters are allowed. We demonstrate that the emergent 2D$2D$ Weitzenbock geometry as well as the emergent U(1)$U\left(1\right)$ gauge field appear. The emergent gauge field is equal to the linear combination of the components of the zweibein. Therefore, we actually deal with the gauge fixed version of the emergent 2+1$2+1$   D$D$ teleparallel gravity. In particular, we work out the case, when the variations of the hopping parameters are due to the elastic deformations, and relate the elastic deformations with the emergent zweibein. Next, we investigate the tight-binding model with the varying intralayer hopping parameters for the multilayer graphene with the ABC$ABC$ stacking. In this case the emergent 2D$2D$ Weitzenbock geometry and the emergent U(1)$U\left(1\right)$ gauge field appear as well, and the emergent low energy effective field theory has the anisotropic scaling.     

On the superconductivity of graphite interfaces

We propose an explanation for the appearance of superconductivity at the interfaces of graphite with Bernal stacking order. A network of line defects with flat bands appears at the interfaces between two slightly twisted graphite structures. Due to the flat band the probability to find high temperature superconductivity at these quasi one-dimensional corridors is strongly enhanced. When the network of superconducting lines is dense it becomes effectively two-dimensional. The model provides an explanation for several reports on the observation of superconductivity up to room temperature in different oriented graphite samples, graphite powders as well as graphite-composite samples published in the past.     

Negative Temperature: Further Extensions

JETP Letters - This work is motivated by the recent paper [M. Baldovin, S. Iubini, R. Livi, and A. Vulpiani, Statistical mechanics of systems with negative temperature, arXiv:2103.12572]. The...     

Tetrads in Solids: from Elasticity Theory to Topological Quantum Hall Systems and Weyl Fermions

Journal of Experimental and Theoretical Physics - Theory of elasticity in topological insulators has many common features with relativistic quantum fields interacting with gravitational fields in...