23 research outputs found
Electromagnetic fields induced by an electric charge near a Weyl semimetal
[EN] Weyl semimetals (WSM) are a new class of topological materials that exhibit a bulk Hall effect and a chiral magnetic effect. The topological contribution of these unusual electromagnetic responses can be characterized by an axion term θE·B with space and time dependent axion angle θ(r,t). In this paper we compute the electromagnetic fields produced by an electric charge near a topological Weyl semimetal with two Weyl nodes, in the equilibrium state, at zero electric chemical potential, and with broken time-reversal symmetry. We find that, as in ordinary metals and dielectrics, outside the WSM the electric field is mainly determined by the optical properties of the material. The magnetic field is, on the contrary, of topological origin due to the magnetoelectric effect of topological phases. We show that the magnetic field exhibits an interesting behavior above the WSM as compared with that induced above a topological insulator: the field lines begin at the surface and then end at the surface (but not at the same point). This distinctive behavior of the magnetic field is an experimentally observable signature of the anomalous Hall effect in the bulk of the WSM. We discuss two experimental setups for testing our predictions of the induced magnetic field.We thank Alberto Cortijo for useful comments and suggestions, and also to the anonymous referees for their recommendations. A.M. was supported by the CONACyT postdoctoral
Grant No. 234774. L.F.U. has been supported in part by the project CONACyT (México) No. 237503. M.C. has been partially supported by UNAB DGID under Grant No. DI-33-17/RG and wishes to thank A. Martín-Ruiz and L. F. Urrutia at Instituto de Ciencias Nucleares, UNAM for the kind hospitality of throughout the preparation of the manuscript
Hamiltonian LGT in the complete Fourier analysis basis
The main problem in the Hamiltonian formulation of Lattice Gauge Theories is
the determination of an appropriate basis avoiding the over-completeness
arising from Mandelstam relations. We short-cut this problem using Harmonic
analysis on Lie-Groups and intertwining operators formalism to explicitly
construct a basis of the Hilbert space. Our analysis is based only on
properties of the tensor category of Lie-Group representations. The Hamiltonian
of such theories is calculated yielding a sparse matrix whose spectrum and
eigenstates could be exactly derived as functions of the coupling Comment: LATTICE99 (theoretical developments), 3 page
An Alternative Canonical Approach to the Ghost Problem in a Complexified Extension of the Pais-Uhlenbeck Oscillator
Our purpose in this paper is to analyze the Pais-Uhlenbeck (PU) oscillator using complex canonical transformations. We show that starting from a Lagrangian approach we obtain a transformation that makes the extended PU oscillator, with unequal frequencies, to be equivalent to two standard second order oscillators which have the original number of degrees of freedom. Such extension is provided by adding a total time derivative to the PU Lagrangian together with a complexification of the original variables further subjected to reality conditions in order to maintain the required number of degrees of freedom. The analysis is accomplished at both the classical and quantum levels. Remarkably, at the quantum level the negative norm states are eliminated, as well as the problems of unbounded below energy and non-unitary time evolution. We illustrate the idea of our approach by eliminating the negative norm states in a complex oscillator. Next, we extend the procedure to the Pais-Uhlenbeck oscillator. The corresponding quantum propagators are calculated using Schwinger's quantum action principle. We also discuss the equal frequency case at the classical level
The basis of the physical Hilbert space of lattice gauge theories
Non-linear Fourier analysis on compact groups is used to construct an
orthonormal basis of the physical (gauge invariant) Hilbert space of
Hamiltonian lattice gauge theories. In particular, the matrix elements of the
Hamiltonian operator involved are explicitly computed. Finally, some
applications and possible developments of the formalism are discussed.Comment: 14 pages, LaTeX (Using amsmath
Faraday effect : a field theoretical point of view
We analyze the structure of the vacuum polarization tensor in the presence of
a background electromagnetic field in a medium. We use various discrete
symmetries and crossing symmetry to constrain the form factors obtained for the
most general case. From these symmetry arguments, we show why the vacuum
polarization tensor has to be even in the background field when there is no
background medium. Taking then the background field to be purely magnetic, we
evaluate the vacuum polarization to linear order in it. The result shows the
phenomenon of Faraday rotation, i.e., the rotation of the plane of polarization
of a plane polarized light passing through this background. We find that the
usual expression for Faraday rotation, which is derived for a non-degenerate
plasma in the non-relativistic approximation, undergoes substantial
modification if the background is degenerate and/or relativistic. We give
explicit expressions for Faraday rotation in completely degenerate and
ultra-relativistic media.Comment: 20 pages, Latex, uses axodraw.st
Universal Hidden Supersymmetry in Classical Mechanics and its Local Extension
We review here a path-integral approach to classical mechanics and explore
the geometrical meaning of this construction. In particular we bring to light a
universal hidden BRS invariance and its geometrical relevance for the Cartan
calculus on symplectic manifolds. Together with this BRS invariance we also
show the presence of a universal hidden genuine non-relativistic supersymmetry.
In an attempt to understand its geometry we make this susy local following the
analogous construction done for the supersymmetric quantum mechanics of Witten.Comment: 6 pages, latex, Volkov Memorial Proceeding
On the consistency of Constraints in Matter Field Theories
We consider how the principles of causality and equivalence restrict the
background in which matter field theories are defined; those constraints
develop in restrictions for these matter field theories: the simplest matter
field theory aside, all other less simple matter field theories are too complex
therefore resulting to be inconsistent in general instances.Comment: 10 page
Axial vector current in an electromagnetic field and low-energy neutrino-photon interactions
An expression for the axial vector current in a strong, slowly varying
electromagnetic field is obtained. We apply this expression to the construction
of the effective action for low-energy neutrino-photon interactions.Comment: 6 pages, references updated, final version to appear in Phys. Rev.
Looking for magnetic monopoles at LHC with diphoton events
Magnetic monopoles have been a subject of interest since Dirac established
the relation between the existence of monopoles and charge quantization. The
intense experimental search carried thus far has not met with success. The
Large Hadron Collider is reaching energies never achieved before allowing the
search for exotic particles in the TeV mass range. In a continuing effort to
discover these rare particles we propose here other ways to detect them. We
study the observability of monopoles and monopolium, a monopole-antimonopole
bound state, at the Large Hadron Collider in the channel for
monopole masses in the range 500-1000 GeV. We conclude that LHC is an ideal
machine to discover monopoles with masses below 1 TeV at present running
energies and with 5 fb of integrated luminosity.Comment: This manuscript contains information appeared in Looking for magnetic
monopoles at LHC, arXiv:1104.0218 [hep-ph] and Monopolium detection at the
LHC.,arXiv:1107.3684 [hep-ph] by the same authors, rewritten for joint
publication in The European Physica Journal Plus. 26 pages, 22 figure
QED Effective Action at Finite Temperature: Two-Loop Dominance
We calculate the two-loop effective action of QED for arbitrary constant
electromagnetic fields at finite temperature T in the limit of T much smaller
than the electron mass. It is shown that in this regime the two-loop
contribution always exceeds the influence of the one-loop part due to the
thermal excitation of the internal photon. As an application, we study light
propagation and photon splitting in the presence of a magnetic background field
at low temperature. We furthermore discover a thermally induced contribution to
pair production in electric fields.Comment: 34 pages, 4 figures, LaTe