48 research outputs found
Reconstruction of Separable Particle Verbs in a Corpus of Spoken German
We present a method for detecting and reconstructing separated particle verbs in a corpus of spoken German by following an approach suggested for written language. Our study shows that the method can be applied successfully to spoken language, compares different ways of dealing with structures that are specific to spoken language corpora, analyses some remaining problems, and discusses ways of optimising precision or recall for the method. The outlook sketches some possibilities for further work in related areas
The General Warped Solution with Conical Branes in Six-dimensional Supergravity
We present the general regular warped solution with 4D Minkowski spacetime in
six-dimensional gauged supergravity. In this framework, we can easily embed
multiple conical branes into the warped geometry by choosing an undetermined
holomorphic function. As an example, for the holomorphic function with many
zeroes, we find warped solutions with multi-branes and discuss the generalized
flux quantization in this case.Comment: 1+19 pages, no figure, JHEP style, version to appear in JHE
Local SU(5) Unification from the Heterotic String
We construct a 6D supergravity theory which emerges as intermediate step in
the compactification of the heterotic string to the supersymmetric standard
model in four dimensions. The theory has N=2 supersymmetry and a gravitational
sector with one tensor and two hypermultiplets in addition to the supergravity
multiplet. Compactification to four dimensions occurs on a T^2/Z_2 orbifold
which has two inequivalent pairs of fixed points with unbroken SU(5) and
SU(2)xSU(4) symmetry, respectively. All gauge, gravitational and mixed
anomalies are cancelled by the Green-Schwarz mechanism. The model has partial
6D gauge-Higgs unification. Two quark-lepton generations are localized at the
SU(5) branes, the third family is composed of split bulk hypermultiplets. The
top Yukawa coupling is given by the 6D gauge coupling, all other Yukawa
couplings are generated by higher-dimensional operators at the SU(5) branes.
The presence of the SU(2)xSU(4) brane breaks SU(5) and generates split gauge
and Higgs multiplets with N=1 supersymmetry in four dimensions. The third
generation is obtained from two split \bar{5}-plets and two split 10-plets,
which together have the quantum numbers of one \bar{5}-plet and one 10-plet.
This avoids unsuccessful SU(5) predictions for Yukawa couplings of ordinary 4D
SU(5) grand unified theories.Comment: 38 pages. v2: Typos correcte
Building SO(10) models from F-theory
We revisit local F-theory SO(10) and SU(5) GUTs and analyze their properties
within the framework of the maximal underlying E_8 symmetry in the elliptic
fibration. We consider the symmetry enhancements along the intersections of
seven-branes with the GUT surface and study in detail the embedding of the
abelian factors undergoing monodromies in the covering gauge groups. We combine
flux data from the successive breaking of SO(10) to SU(5) gauge symmetry and
subsequently to the Standard Model one, and further constrain the parameters
determining the models' particle spectra. In order to eliminate dangerous
baryon number violating operators we propose ways to construct matter parity
like symmetries from intrinsic geometric origin. We study implementations of
the resulting constrained scenario in specific examples obtained for a variety
of monodromies.Comment: 53 page
Preverbs: an introduction
The notion ‘preverb’ is a traditional descriptive notion in Indo-European linguistics. It refers to morphemes that appear
in front of a verb, and which form a close semantic unit with that verb. In many cases, the morpheme that functions as a preverb
can also function without a preverbal context, often as an adverb or an adposition. Most linguists use the notion ‘preverb’
as a cover term for preverbal words and preverbal prefixes. The preverb may be separated from the verb whilst retaining its
close cohesion with the verb, which is called ‘tmesis’. It may also develop into a bound morpheme, that is, a prefix inseparable
from the verb, with concomitant reduction of phonological form in some cases. If the preverb has become a real prefix, we
may use the more specific notion of ‘complex verb’, whereas we take the notion ‘complex predicate’ to refer generally to multi-morphemic
expressions with verbal valency. That is, we make a terminological distinction between complex predicates and complex verbs.
The latter are multi-morphemic, but behave as single grammatical words
U(n) Spectral Covers from Decomposition
We construct decomposed spectral covers for bundles on elliptically fibered
Calabi-Yau threefolds whose structure groups are S(U(1) x U(4)), S(U(2) x U(3))
and S(U(1) x U(1) x U(3)) in heterotic string compactifications. The
decomposition requires not only the tuning of the SU(5) spectral covers but
also the tuning of the complex structure moduli of the Calabi-Yau threefolds.
This configuration is translated to geometric data on F-theory side. We find
that the monodromy locus for two-cycles in K3 fibered Calabi-Yau fourfolds in a
stable degeneration limit is globally factorized with squared factors under the
decomposition conditions. This signals that the monodromy group is reduced and
there is a U(1) symmetry in a low energy effective field theory. To support
that, we explicitly check the reduction of a monodromy group in an appreciable
region of the moduli space for an gauge theory with (1+2) decomposition.
This may provide a systematic way for constructing F-theory models with U(1)
symmetries.Comment: 41 pages, 14 figures; v2: minor improvements and a reference adde
Discrete R-symmetries and Anomaly Universality in Heterotic Orbifolds
We study discrete R-symmetries, which appear in 4D low energy effective field
theory derived from hetetoric orbifold models. We derive the R-symmetries
directly from geometrical symmetries of orbifolds. In particular, we obtain the
corresponding R-charges by requiring that the couplings be invariant under
these symmetries. This allows for a more general treatment than the explicit
computations of correlation functions made previously by the authors, including
models with discrete Wilson lines, and orbifold symmetries beyond
plane-by-plane rotational invariance. Surprisingly, for the cases covered by
earlier explicit computations, the R-charges differ from the previous result.
We study the anomalies associated with these R-symmetries, and comment on the
results.Comment: 21 pages, 2 figures. Minor changes, typos corrected. Matches JHEP
published versio
Massive Abelian Gauge Symmetries and Fluxes in F-theory
F-theory compactified on a Calabi-Yau fourfold naturally describes
non-Abelian gauge symmetries through the singularity structure of the elliptic
fibration. In contrast Abelian symmetries are more difficult to study because
of their inherently global nature. We argue that in general F-theory
compactifications there are massive Abelian symmetries, such as the uplift of
the Abelian part of the U(N) gauge group on D7-branes, that arise from
non-Kahler resolutions of the dual M-theory setup. The four-dimensional
F-theory vacuum with vanishing expectation values for the gauge fields
corresponds to the Calabi-Yau limit. We propose that fluxes that are turned on
along these U(1)s are uplifted to non-harmonic four-form fluxes. We derive the
effective four-dimensional gauged supergravity resulting from F-theory
compactifications in the presence of the Abelian gauge factors including the
effects of possible fluxes on the gauging, tadpoles and matter spectrum.Comment: 49 page
Rational F-Theory GUTs without exotics
We construct F-theory GUT models without exotic matter, leading to the MSSM
matter spectrum with potential singlet extensions. The interplay of engineering
explicit geometric setups, absence of four-dimensional anomalies, and realistic
phenomenology of the couplings places severe constraints on the allowed local
models in a given geometry. In constructions based on the spectral cover we
find no model satisfying all these requirements. We then provide a survey of
models with additional U(1) symmetries arising from rational sections of the
elliptic fibration in toric constructions and obtain phenomenologically
appealing models based on SU(5) tops. Furthermore we perform a bottom-up
exploration beyond the toric section constructions discussed in the literature
so far and identify benchmark models passing all our criteria, which can serve
as a guideline for future geometric engineering.Comment: 27 Pages, 1 Figur
Fixing D7 Brane Positions by F-Theory Fluxes
To do realistic model building in type IIB supergravity, it is important to
understand how to fix D7-brane positions by the choice of fluxes. More
generally, F-theory model building requires the understanding of how fluxes
determine the singularity structure (and hence gauge group and matter content)
of the compactification. We analyse this problem in the simple setting of
M-theory on K3xK3. Given a certain flux which is consistent with the F-theory
limit, we can explicitly derive the positions at which D7 branes or stacks of
D7 branes are stabilised. The analysis is based on a parameterization of the
moduli space of type IIB string theory on T^2/Z_2 (including D7-brane
positions) in terms of the periods of integral cycles of M-theory on K3. This
allows us, in particular, to select a specific desired gauge group by the
choice of flux numbers.Comment: 41 pages, 2 figures; latex font correcte