917 research outputs found
Custodial Leptons and Higgs Decays
We study the effects of extended fermion sectors, respecting custodial
symmetry, on Higgs production and decay. The resulting protection for the
Z->b_L b_L and Z->\tau_R\tau_R decays allows for potentially interesting
signals in Higgs physics, while maintaining the good agreement of the Standard
Model with precision tests, without significant fine-tuning. Although being
viable setups on their own, the models we study can particularly be motivated
as the low energy effective theories of the composite Higgs models MCHM_5 and
MCHM_10 or the corresponding gauge-Higgs unification models. The spectra can be
identified with the light custodians present in these theories. These have the
potential to describe the relevant physics in their fermion sectors in a
simplified and transparent way. In contrast to previous studies of composite
models, we consider the impact of a realistic lepton sector on the Higgs
decays. We find significant modifications in the decays to \tau leptons and
photons due to the new leptonic resonances. While from a pure low energy
perspective an enhancement of the channel pp->h->\gamma\gamma turns out to be
possible, if one considers constraints on the parameters from the full
structure of the composite models, the decay mode into photons is always
reduced. We also demonstrate that taking into account the non-linearity of the
Higgs sector does not change the qualitative picture for the decays into
\tau-leptons or photons in the case of the dominant Higgs production mechanism.Comment: 33 pages, 12 figures; v2: typos corrected, references added, minor
clarifying comments and discussion of new Moriond results added, version
published in JHE
D-brane Instantons as Gauge Instantons in Orientifolds of Chiral Quiver Theories
Systems of D3-branes at orientifold singularities can receive
non-perturbative D-brane instanton corrections, inducing field theory operators
in the 4d effective theory. In certain non-chiral examples, these systems have
been realized as the infrared endpoint of a Seiberg duality cascade, in which
the D-brane instanton effects arise from strong gauge theory dynamics. We
present the first UV duality cascade completion of chiral D3-brane theories, in
which the D-brane instantons arise from gauge theory dynamics. Chiral examples
are interesting because the instanton fermion zero mode sector is topologically
protected, and therefore lead to more robust setups. As an application of our
results, we provide a UV completion of certain D-brane orientifold systems
recently claimed to produce conformal field theories with conformal invariance
broken only by D-brane instantons.Comment: 50 pages, 32 figures. v2: version published in JHEP with references
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The Missing Data Encoder: Cross-Channel Image Completion\\with Hide-And-Seek Adversarial Network
Image completion is the problem of generating whole images from fragments
only. It encompasses inpainting (generating a patch given its surrounding),
reverse inpainting/extrapolation (generating the periphery given the central
patch) as well as colorization (generating one or several channels given other
ones). In this paper, we employ a deep network to perform image completion,
with adversarial training as well as perceptual and completion losses, and call
it the ``missing data encoder'' (MDE). We consider several configurations based
on how the seed fragments are chosen. We show that training MDE for ``random
extrapolation and colorization'' (MDE-REC), i.e. using random
channel-independent fragments, allows a better capture of the image semantics
and geometry. MDE training makes use of a novel ``hide-and-seek'' adversarial
loss, where the discriminator seeks the original non-masked regions, while the
generator tries to hide them. We validate our models both qualitatively and
quantitatively on several datasets, showing their interest for image
completion, unsupervised representation learning as well as face occlusion
handling
Reactor mixing angle from hybrid neutrino masses
In terms of its eigenvector decomposition, the neutrino mass matrix (in the
basis where the charged lepton mass matrix is diagonal) can be understood as
originating from a tribimaximal dominant structure with small deviations, as
demanded by data. If neutrino masses originate from at least two different
mechanisms, referred to as "hybrid neutrino masses", the experimentally
observed structure naturally emerges provided one mechanism accounts for the
dominant tribimaximal structure while the other is responsible for the
deviations. We demonstrate the feasibility of this picture in a fairly
model-independent way by using lepton-number-violating effective operators,
whose structure we assume becomes dictated by an underlying flavor
symmetry. We show that if a second mechanism is at work, the requirement of
generating a reactor angle within its experimental range always fixes the solar
and atmospheric angles in agreement with data, in contrast to the case where
the deviations are induced by next-to-leading order effective operators. We
prove this idea is viable by constructing an -based ultraviolet
completion, where the dominant tribimaximal structure arises from the type-I
seesaw while the subleading contribution is determined by either type-II or
type-III seesaw driven by a non-trivial singlet (minimal hybrid model).
After finding general criteria, we identify all the symmetries
capable of producing such -based minimal hybrid models.Comment: 18 pages, 5 figures. v3: section including sum rules added, accepted
by JHE
Mass corrections in string theory and lattice field theory
Kaluza-Klein compactifications of higher dimensional Yang-Mills theories
contain a number of four dimensional scalars corresponding to the internal
components of the gauge field. While at tree-level the scalar zero modes are
massless, it is well known that quantum corrections make them massive. We
compute these radiative corrections at 1-loop in an effective field theory
framework, using the background field method and proper Schwinger-time
regularization. In order to clarify the proper treatment of the sum over
KK--modes in the effective field theory approach, we consider the same problem
in two different UV completions of Yang-Mills: string theory and lattice field
theory. In both cases, when the compactification radius is much bigger than
the scale of the UV completion (), we recover a mass
renormalization that is independent of the UV scale and agrees with the one
derived in the effective field theory approach. These results support the idea
that the value of the mass corrections is, in this regime, universal for any UV
completion that respects locality and gauge invariance. The string analysis
suggests that this property holds also at higher loops. The lattice analysis
suggests that the mass of the adjoint scalars appearing in
Super Yang-Mills is highly suppressed due to an interplay between the
higher-dimensional gauge invariance and the degeneracy of bosonic and fermionic
degrees of freedom.Comment: 27 page
Broken Symmetry as a Stabilizing Remnant
The Goldberger-Wise mechanism enables one to stabilize the length of the
warped extra dimension employed in Randall-Sundrum models. In this work we
generalize this mechanism to models with multiple warped throats sharing a
common ultraviolet brane. For independent throats this generalization is
straight forward. If the throats possess a discrete interchange symmetry like
Z_n the stabilizing dynamics may respect the symmetry, resulting in equal
throat lengths, or they may break it. In the latter case the ground state of an
initially symmetric configuration is a stabilized asymmetric configuration in
which the throat lengths differ. We focus on two- (three-) throat setups with a
Z_2 (Z_3) interchange symmetry and present stabilization dynamics suitable for
either breaking or maintaining the symmetry. Though admitting more general
application, our results are relevant for existing models in the literature,
including the two throat model with Kaluza-Klein parity and the three throat
model of flavor based on a broken Z_3 symmetry.Comment: 23 pages; v2 minor cosmetic chang
Machine Psychology: Investigating Emergent Capabilities and Behavior in Large Language Models Using Psychological Methods
Large language models (LLMs) are currently at the forefront of intertwining
AI systems with human communication and everyday life. Due to rapid
technological advances and their extreme versatility, LLMs nowadays have
millions of users and are at the cusp of being the main go-to technology for
information retrieval, content generation, problem-solving, etc. Therefore, it
is of great importance to thoroughly assess and scrutinize their capabilities.
Due to increasingly complex and novel behavioral patterns in current LLMs, this
can be done by treating them as participants in psychology experiments that
were originally designed to test humans. For this purpose, the paper introduces
a new field of research called "machine psychology". The paper outlines how
different subfields of psychology can inform behavioral tests for LLMs. It
defines methodological standards for machine psychology research, especially by
focusing on policies for prompt designs. Additionally, it describes how
behavioral patterns discovered in LLMs are to be interpreted. In sum, machine
psychology aims to discover emergent abilities in LLMs that cannot be detected
by most traditional natural language processing benchmarks
Implicit Feature Networks for Texture Completion from Partial 3D Data
Prior work to infer 3D texture use either texture atlases, which require
uv-mappings and hence have discontinuities, or colored voxels, which are memory
inefficient and limited in resolution. Recent work, predicts RGB color at every
XYZ coordinate forming a texture field, but focus on completing texture given a
single 2D image. Instead, we focus on 3D texture and geometry completion from
partial and incomplete 3D scans. IF-Nets have recently achieved
state-of-the-art results on 3D geometry completion using a multi-scale deep
feature encoding, but the outputs lack texture. In this work, we generalize
IF-Nets to texture completion from partial textured scans of humans and
arbitrary objects. Our key insight is that 3D texture completion benefits from
incorporating local and global deep features extracted from both the 3D partial
texture and completed geometry. Specifically, given the partial 3D texture and
the 3D geometry completed with IF-Nets, our model successfully in-paints the
missing texture parts in consistence with the completed geometry. Our model won
the SHARP ECCV'20 challenge, achieving highest performance on all challenges.Comment: SHARP Workshop, European Conference on Computer Vision (ECCV), 202
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