10,038 research outputs found
T-Branes and Geometry
T-branes are a non-abelian generalization of intersecting branes in which the
matrix of normal deformations is nilpotent along some subspace. In this paper
we study the geometric remnant of this open string data for six-dimensional
F-theory vacua. We show that in the dual M-theory / IIA compactification on a
smooth Calabi-Yau threefold X, the geometric remnant of T-brane data translates
to periods of the three-form potential valued in the intermediate Jacobian of
X. Starting from a smoothing of a singular Calabi-Yau, we show how to track
this data in singular limits using the theory of limiting mixed Hodge
structures, which in turn directly points to an emergent Hitchin-like system
coupled to defects. We argue that the physical data of an F-theory
compactification on a singular threefold involves specifying both a geometry as
well as the remnant of three-form potential moduli and flux which is localized
on the discriminant. We give examples of T-branes in compact F-theory models
with heterotic duals, and comment on the extension of our results to
four-dimensional vacua.Comment: v2: 80 pages, 2 figures, clarifications and references added, typos
correcte
Revisiting the optical -symmetric dimer
Optics has proved a fertile ground for the experimental simulation of quantum
mechanics. Most recently, optical realizations of -symmetric
quantum mechanics have been shown, both theoretically and experimentally,
opening the door to international efforts aiming at the design of practical
optical devices exploiting this symmetry. Here, we focus on the optical
-symmetric dimer, a two-waveguide coupler were the materials show
symmetric effective gain and loss, and provide a review of the linear and
nonlinear optical realizations from a symmetry based point of view. We go
beyond a simple review of the literature and show that the dimer is just the
smallest of a class of planar -waveguide couplers that are the optical
realization of Lorentz group in 2+1 dimensions. Furthermore, we provide a
formulation to describe light propagation through waveguide couplers described
by non-Hermitian mode coupling matrices based on a non-Hermitian generalization
of Ehrenfest theorem.Comment: 25 pages, 12 figure
T-Branes at the Limits of Geometry
Singular limits of 6D F-theory compactifications are often captured by
T-branes, namely a non-abelian configuration of intersecting 7-branes with a
nilpotent matrix of normal deformations. The long distance approximation of
such 7-branes is a Hitchin-like system in which simple and irregular poles
emerge at marked points of the geometry. When multiple matter fields localize
at the same point in the geometry, the associated Higgs field can exhibit
irregular behavior, namely poles of order greater than one. This provides a
geometric mechanism to engineer wild Higgs bundles. Physical constraints such
as anomaly cancellation and consistent coupling to gravity also limit the order
of such poles. Using this geometric formulation, we unify seemingly different
wild Hitchin systems in a single framework in which orders of poles become
adjustable parameters dictated by tuning gauge singlet moduli of the F-theory
model.Comment: v2: 65 pages, 6 figures, clarifications adde
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