10,783 research outputs found
Vortes solutions in nonabelian Higgs theories
A new class of vortex solutions is found in SU(2) gauge theories with two
adjoint representation Higgs bosons. Implications of these new solutions and
their possible connection with Center Gauge fixed pure gauge theories are
discussed.Comment: 8 pages, added references, other changes, including title and
abstrac
Strings Next To and Inside Black Holes
The string equations of motion and constraints are solved near the horizon
and near the singularity of a Schwarzschild black hole. In a conformal gauge
such that ( = worldsheet time coordinate) corresponds to the
horizon () or to the black hole singularity (), the string
coordinates express in power series in near the horizon and in power
series in around . We compute the string invariant size and
the string energy-momentum tensor. Near the horizon both are finite and
analytic. Near the black hole singularity, the string size, the string energy
and the transverse pressures (in the angular directions) tend to infinity as
. To leading order near , the string behaves as two dimensional
radiation. This two spatial dimensions are describing the sphere in the
Schwarzschild manifold.Comment: RevTex, 19 pages without figure
Linear Response Theory and Optical Conductivity of Floquet Topological Insulators
Motivated by the quest for experimentally accessible dynamical probes of
Floquet topological insulators, we formulate the linear response theory of a
periodically driven system. We illustrate the applications of this formalism by
giving general expressions for optical conductivity of Floquet systems,
including its homodyne and heterodyne components and beyond. We obtain the
Floquet optical conductivity of specific driven models, including
two-dimensional Dirac material such as the surface of a topological insulator,
graphene, and the Haldane model irradiated with circularly or linearly
polarized laser, as well as semiconductor quantum well driven by an ac
potential. We obtain approximate analytical expressions and perform numerically
exact calculations of the Floquet optical conductivity in different scenarios
of the occupation of the Floquet bands, in particular, the diagonal Floquet
distribution and the distribution obtained after a quench. We comment on
experimental signatures and detection of Floquet topological phases using
optical probes.Comment: 16 pages, 10 figure
Revisiting Minimal Lepton Flavour Violation in the Light of Leptonic CP Violation
The Minimal Lepton Flavour Violation (MLFV) framework is discussed after the
recent indication for CP violation in the leptonic sector. Among the three
distinct versions of MLFV, the one with degenerate right-handed neutrinos will
be disfavoured, if this indication is confirmed. The predictions for leptonic
radiative rare decays and muon conversion in nuclei are analysed, identifying
strategies to disentangle the different MLFV scenarios. The claim that the
present anomalies in the semi-leptonic -meson decays can be explained within
the MLFV context is critically re-examined concluding that such an explanation
is not compatible with the present bounds from purely leptonic processes.Comment: 36 pages, 4 figures. V2: References added; version accepted for
publication on JHE
Strings in Cosmological and Black Hole Backgrounds: Ring Solutions
The string equations of motion and constraints are solved for a ring shaped
Ansatz in cosmological and black hole spacetimes. In FRW universes with
arbitrary power behavior [R(X^0) = a\;|X^0|^{\a}\, ], the asymptotic form of
the solution is found for both and and we plot the
numerical solution for all times. Right after the big bang (), the
string energy decreasess as and the string size grows as for . Very
soon [ ] , the ring reaches its oscillatory regime with frequency
equal to the winding and constant size and energy. This picture holds for all
values of \a including string vacua (for which, asymptotically, \a = 1).
In addition, an exact non-oscillatory ring solution is found. For black hole
spacetimes (Schwarzschild, Reissner-Nordstr\oo m and stringy), we solve for
ring strings moving towards the center. Depending on their initial conditions
(essentially the oscillation phase), they are are absorbed or not by
Schwarzschild black holes. The phenomenon of particle transmutation is
explicitly observed (for rings not swallowed by the hole). An effective horizon
is noticed for the rings. Exact and explicit ring solutions inside the
horizon(s) are found. They may be interpreted as strings propagating between
the different universes described by the full black hole manifold.Comment: Paris preprint PAR-LPTHE-93/43. Uses phyzzx. Includes figures. Text
and figures compressed using uufile
Recursive POD expansion for the advection-diffusion-reaction equation
This paper deals with the approximation of advection-diffusion-reaction
equation solution by reduced order methods. We use the Recursive POD approximation for multivariate functions introduced in [M. AZAÏEZ, F. BEN BELGACEM, T. CHACÓN REBOLLO, Recursive POD expansion for reactiondiffusion equation, Adv.Model. and Simul. in Eng. Sci. (2016) 3:3. DOI 10.1186/s40323-016-0060-1] and applied to the low tensor representation
of the solution of the reaction-diffusion partial differential equation. In this
contribution we extend the Recursive POD approximation for multivariate functions with an arbitrary number of parameters, for which we prove general error estimates. The method is used to approximate the solutions of the advection-diffusion-reaction equation. We prove spectral error estimates, in which the spectral convergence rate depends only on the diffusion interval, while the error estimates are affected by a factor that grows exponentially with the advection velocity, and are independent of the reaction rate if this lives in a bounded set. These error estimates are based upon the analyticity of the solution of these equations as a function of the parameters (advection
velocity, diffusion, reaction rate). We present several numerical tests, strongly consistent with the theoretical error estimates.Ministerio de Economía y CompetitividadAgence nationale de la rechercheGruppo Nazionale per il Calcolo ScientificoUE ERA-PLANE
Strings Propagating in the 2+1 Dimensional Black Hole Anti de Sitter Spacetime
We study the string propagation in the 2+1 black hole anti de Sitter
background (2+1 BH-ADS). We find the first and second order fluctuations around
the string center of mass and obtain the expression for the string mass. The
string motion is stable, all fluctuations oscillate with real frequencies and
are bounded, even at We compare with the string motion in the ordinary
black hole anti de Sitter spacetime, and in the black string background, where
string instabilities develop and the fluctuations blow up at We find the
exact general solution for the circular string motion in all these backgrounds,
it is given closely and completely in terms of elliptic functions. For the
non-rotating black hole backgrounds the circular strings have a maximal bounded
size they contract and collapse into No indefinitely growing
strings, neither multi-string solutions are present in these backgrounds. In
rotating spacetimes, both the 2+1 BH-ADS and the ordinary Kerr-ADS, the
presence of angular momentum prevents the string from collapsing into
The circular string motion is also completely solved in the black hole de
Sitter spacetime and in the black string background (dual of the 2+1 BH-ADS
spacetime), in which expanding unbounded strings and multi-string solutions
appear.Comment: Latex, 54 pages + 2 tables and 4 figures (not included). PARIS-DEMIRM
94/01
A local and integrable lattice regularization of the massive Thirring model
The light--cone lattice approach to the massive Thirring model is
reformulated using a local and integrable lattice Hamiltonian written in terms
of discrete fermi fields. Several subtle points concerning boundary conditions,
normal--ordering, continuum limit, finite renormalizations and decoupling of
fermion doublers are elucidated. The relations connecting the six--vertex
anisotropy and the various coupling constants of the continuum are analyzed in
detail.Comment: Latex, 24 pages, some corrected misprints and minor changes, 2
Postscript figures unchange
New vortex solution in SU(3) gauge-Higgs theory
Following a brief review of known vortex solutions in SU(N) gauge-adjoint
Higgs theories we show the existence of a new ``minimal'' vortex solution in
SU(3) gauge theory with two adjoint Higgs bosons. At a critical coupling the
vortex decouples into two abelian vortices, satisfying Bogomol'nyi type, first
order, field equations. The exact value of the vortex energy (per unit length)
is found in terms of the topological charge that equals to the N=2
supersymmetric charge, at the critical coupling. The critical coupling signals
the increase of the underlying supersymmetry.Comment: 15 page
- …