1,912 research outputs found
Matter From Geometry Without Resolution
We utilize the deformation theory of algebraic singularities to study charged
matter in compactifications of M-theory, F-theory, and type IIa string theory
on elliptically fibered Calabi-Yau manifolds. In F-theory, this description is
more physical than that of resolution. We describe how two-cycles can be
identified and systematically studied after deformation. For ADE singularities,
we realize non-trivial ADE representations as sublattices of Z^N, where N is
the multiplicity of the codimension one singularity before deformation. We give
a method for the determination of Picard-Lefschetz vanishing cycles in this
context and utilize this method for one-parameter smooth deformations of ADE
singularities. We give a general map from junctions to weights and demonstrate
that Freudenthal's recursion formula applied to junctions correctly reproduces
the structure of high-dimensional ADE representations, including the 126 of
SO(10) and the 43,758 of E_6. We identify the Weyl group action in some
examples, and verify its order in others. We describe the codimension two
localization of matter in F-theory in the case of heterotic duality or simple
normal crossing and demonstrate the branching of adjoint representations.
Finally, we demonstrate geometrically that deformations correctly reproduce the
appearance of non-simply-laced algebras induced by monodromy around codimension
two singularities, showing the reduction of D_4 to G_2 in an example. A
companion mathematical paper will follow.Comment: 30 pages + references, appendices. v2: references and two figures
added, typos correcte
Non-Abelian Gauge Symmetry and the Higgs Mechanism in F-theory
Singular fiber resolution does not describe the spontaneous breaking of gauge
symmetry in F-theory, as the corresponding branch of the moduli space does not
exist in the theory. Accordingly, even non-abelian gauge theories have not been
fully understood in global F-theory compactifications. We present a systematic
discussion of using singularity deformation, which does describe the
spontaneous breaking of gauge symmetry in F-theory, to study non-abelian gauge
symmetry. Since this branch of the moduli space also exists in the defining
M-theory compactification, it provides the only known description of gauge
theory states which exists in both pictures; they are string junctions in
F-theory. We discuss how global deformations give rise to local deformations,
and also give examples where local deformation can be utilized even in models
where a global deformation does not exist. Utilizing deformations, we study a
number of new examples, including non-perturbative descriptions of and
gauge theories on seven-branes which do not admit a weakly coupled type
IIb description. It may be of phenomenological interest that these
non-perturbative descriptions do not exist for higher rank theories.Comment: 30 pages. v2: Updated codes, added references, and discussed how
local deformation can be utilized even when a global deformation does not
exist (the case of non-Higgsable clusters). v3: final version, published in
Communications in Mathematical Physic
Dualities of Deformed SCFTs from Link Monodromy on D3-brane States
We study D3-brane theories that are dually described as deformations of two
different superconformal theories with massless monopoles and
dyons. These arise at the self-intersection of a seven-brane in F-theory, which
cuts out a link on a small three-sphere surrounding the self-intersection. The
spectrum is studied by taking small loops in the three-sphere, yielding a
link-induced monodromy action on string junction D3-brane states, and
subsequently quotienting by the monodromy. This reduces the differing flavor
algebras of the theories to the same flavor algebra, as
required by duality, and projects out charged states, yielding an
superconformal theory on the D3-brane. In one, a deformation of
a rank one Argyres-Douglas theory retains its flavor symmetry and
exhibits a charge neutral flavor triplet that is comprised of electron, dyon,
and monopole string junctions. From duality we argue that the monodromy
projection should also be imposed away from the conformal point, in which case
the D3-brane field theory appears to exhibit confinement of electrons, dyons,
and monopoles. We will address the mathematical counterparts in a companion
paper.Comment: 28+20 pages, 8 figures 6 table
Metalinguistic Knowledge/Awareness/Ability in Cognitive Translation Studies: Some Questions
 Throughout the history of contemporary Translation Studies, theoretical, empirical and pedagogically oriented work has made use of a range of notions that assume a translator’s metalinguistic knowledge, or knowledge about language, rather than knowledge of a language or languages. Examples include ideas such as ‘translation strategies’, translational ‘problem-solving’, ‘the monitor model’ and models of translator competence. Issues related to learning, automatization, and consciousness also figure in many of the discussions. At the same time, studies in bi- and multilingualism and second (and third) language acquisition have also developed a range of related ideas and concepts to deal with some of the same issues and concerns in bi- and multilingual language production more broadly (see e.g. Jessner 2006: 40-43). Some recent translation process studies have begun to target questions related to metalinguistic awareness (e.g. Ehrensberger-Dow/Künzli 2010, Ehrensberger-Dow/Perrin 2009) while the underlying assumptions of some of the commonly used ideas are also being questioned (e.g. Muñoz MartÃn 2016a). The range of available ideas, the significant differences between them, and the increasingly important role these ideas are playing in cognitive translation research mandate a critical look at this conceptual field. In this paper, I present some current views on metalinguistic knowledge/awareness/ability within the bi- and multilingualism and second language acquisition (SLA) literature, and compare these to some of the most widely used constructs in Cognitive Translation Studies (CTS). The aim is to clear the conceptual ground and to single out some of the most pressing questions to be addressed regarding this particular aspect of translational cognition.Â
How Leaders Invest Staffing Resources for Learning Improvement
Analyzes staffing challenges that guide school leaders' resource decisions in the context of a learning improvement agenda, staff resource investment strategies that improve learning outcomes equitably, and ways to win support for differential investment
Geometry and Topology of String Junctions
We study elliptic fibrations by analyzing suitable deformations of the
fibrations and vanishing cycles. We introduce geometric string junctions and
describe some of their properties. We show how the structure of the geometric
string junctions is naturally related to the Lie algebra structures of the
associated singularities. One application in physics is in F-theory, where our
novel approach connecting deformations and Lie algebras describes the structure
of generalized type IIB seven-branes and string junction states which end on
them.Comment: 16 pages. v2: additional comments and reference
Cosmological Parameter Extraction from the First Season of Observations with DASI
The Degree Angular Scale Interferometer (\dasi) has measured the power
spectrum of the Cosmic Microwave Background anisotropy over the range of
spherical harmonic multipoles 100<l<900. We compare this data, in combination
with the COBE-DMR results, to a seven dimensional grid of adiabatic CDM models.
Adopting the priors h>0.45 and 0.0<=tau_c<=0.4, we find that the total density
of the Universe Omega_tot=1.04+/-0.06, and the spectral index of the initial
scalar fluctuations n_s=1.01+0.08-0.06, in accordance with the predictions of
inflationary theory. In addition we find that the physical density of baryons
Omega_b.h^2=0.022+0.004-0.003, and the physical density of cold dark matter
Omega_cdm.h^2=0.14+/-0.04. This value of Omega_b.h^2 is consistent with that
derived from measurements of the primordial abundance ratios of the light
elements combined with big bang nucleosynthesis theory. Using the result of the
HST Key Project h=0.72+/-0.08 we find that Omega_t=1.00+/-0.04, the matter
density Omega_m=0.40+/-0.15, and the vacuum energy density
Omega_lambda=0.60+/-0.15. (All 68% confidence limits.)Comment: 7 pages, 4 figures, minor changes in response to referee comment
Possible high-frequency cavity and waveguide applications of high temperature superconductors
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