pinecone/core-2020-05-10-deduplication huggingface dataset:
A Holographic Two-Impurity Kondo Model

We propose a model of a strongly-interacting two-impurity Kondo system based\ud
on the AdS/CFT correspondence, also known as holography. In a Landau Fermi\ud
Liquid, the single-impurity Kondo effect is the screening of an impurity spin\ud
at low temperature $T$. The two-impurity Kondo model then describes the\ud
competition between the Kondo interaction and the Heisenberg interaction\ud
between two impurity spins, also called the RKKY interaction. For spin-$1/2$\ud
impurities, that competition leads to a quantum phase transition from a\ud
Kondo-screened phase to a phase in which the two impurity spins screen one\ud
another. Our holographic model is based on a $(1+1)$-dimensional CFT\ud
description of the two-impurity Kondo model, reliable for two impurities with\ud
negligible separation in space. We consider only impurity spins in a totally\ud
anti-symmetric representation of an $SU(N)$ spin symmetry. We employ a\ud
large-$N$ limit, in which both Kondo and RKKY couplings are double-trace, and\ud
both Kondo and inter-impurity screening appear as condensation of single-trace\ud
operators at the impurities' location. We perform the holographic\ud
renormalization of our model, which allows us to identify the Kondo and RKKY\ud
couplings as boundary conditions on fields in AdS. We numerically compute the\ud
phase diagram of our model in the plane of RKKY coupling versus $T$, finding\ud
evidence for a quantum phase transition from a trivial phase, with neither\ud
Kondo nor inter-impurity screening, to a non-trivial phase, with both Kondo and\ud
anti-ferromagnetic inter-impurity screening. More generally we show, just using\ud
$SU(N)$ representation theory, that ferromagnetic correlations must be absent\ud
at leading order in the large-$N$ limit. Our holographic model may be useful\ud
for studying many open problems involving strongly-interacting quantum\ud
impurities, including for example the Kondo lattice, relevant for describing\ud
the heavy fermion compounds
Holography for anisotropic branes with hyperscaling violation

In this paper, based on the principles of Gauge/gavity duality, we explore
the field theory description of certain special class of strongly coupled
hyperscaling violating QFTs in the presence of scalar deformations near the
\textit{effective} dynamical scale ($ r_F $) of the theory. In the language of
the AdS/CFT duality, the scalar deformations of the above type could be thought
of as being sourced due to some massless scalar excitation in the bulk which
explicitly break the $ SO(2) $ rotational invariance along the spatial
directions of the brane. As a consequence of these deformations, it turns out
that when we probe such QFTs in terms of its non-local observable like, the
entanglement entropy as well as the Wilson operator they indeed receive finite
contributions near the effective dynamical scale ($ r_F $) of the theory.Comment: Version to appear in JHE
Generating Functionals for Quantum Field Theories with Random Potentials

We consider generating functionals for computing correlators in quantum field
theories with random potentials. Examples of such theories include condensed
matter systems with quenched disorder (e.g. spin glass) or cosmological systems
in context of the string theory landscape (e.g. cosmic inflation). We use the
so-called replica trick to define two different generating functionals for
calculating correlators of the quantum fields averaged over a given
distribution of random potentials. The first generating functional is
appropriate for calculating averaged (in-out) amplitudes and involves a single
replica of fields, but the replica limit is taken to an (unphysical) negative
one number of fields outside of the path integral. When the number of replicas
is doubled the generating functional can also be used for calculating averaged
probabilities (squared amplitudes) using the in-in construction. The second
generating functional involves an infinite number of replicas, but can be used
for calculating both in-out and in-in correlators and the replica limits are
taken to only a zero number of fields. We discuss the formalism in details for
a single real scalar field, but the generalization to more fields or to
different types of fields is straightforward. We work out three examples: one
where the mass of scalar field is treated as a random variable and two where
the functional form of interactions is random, one described by a Gaussian
random field and the other by a Euclidean action in the field configuration
space.Comment: 21 pages. Made some changes in Introduction, Sec 5 and discussion. An
  appendix added. Accepted in JHE
Features and stability analysis of non-Schwarzschild black hole in
  quadratic gravity

Black holes are found to exist in gravitational theories with the presence of
quadratic curvature terms and behave differently from the Schwarzschild
solution. We present an exhaustive analysis for determining the quasinormal
modes of a test scalar field propagating in a new class of black hole
backgrounds in the case of pure Einstein-Weyl gravity. Our result shows that
the field decay of quasinormal modes in such a non-Schwarzschild black hole
behaves similarly to the Schwarzschild one, but the decay slope becomes much
smoother due to the appearance of the Weyl tensor square in the background
theory. We also analyze the frequencies of the quasinormal modes in order to
characterize the properties of new back holes, and thus, if these modes can be
the source of gravitational waves, the underlying theories may be testable in
future gravitational wave experiments. We briefly comment on the issue of
quantum (in)stability in this theory at linear order.Comment: 18 pages, 4 figures, 1 table, several references added, version
  published on JHE
Spectrum-doubled Heavy Vector Bosons at the LHC

We study a simple effective field theory incorporating six heavy vector
bosons together with the standard-model field content. The new particles
preserve custodial symmetry as well as an approximate left-right parity
symmetry. The enhanced symmetry of the model allows it to satisfy precision
electroweak constraints and bounds from Higgs physics in a regime where all the
couplings are perturbative and where the amount of fine-tuning is comparable to
that in the standard model itself.
  We find that the model could explain the recently observed excesses in
di-boson processes at invariant mass close to 2 TeV from LHC Run 1 for a range
of allowed parameter space. The masses of all the particles differ by no more
than roughly 10%. In a portion of the allowed parameter space only one of the
new particles has a production cross section large enough to be detectable with
the energy and luminosity of Run 1, both via its decay to WZ and to Wh, while
the others have suppressed production rates. The model can be tested at the
higher-energy and higher-luminosity run of the LHC even for an overall scale of
the new particles higher than 3 TeV.Comment: 23 pages, 7 figures, final version for JHE
Accidental Symmetries and the Conformal Bootstrap

We study an ${\cal N} = 2$ supersymmetric generalization of the
three-dimensional critical $O(N)$ vector model that is described by $N+1$
chiral superfields with superpotential $W = g_1 X \sum_i Z_i^2 + g_2 X^3$. By
combining the tools of the conformal bootstrap with results obtained through
supersymmetric localization, we argue that this model exhibits a symmetry
enhancement at the infrared superconformal fixed point due to $g_2$ flowing to
zero. This example is special in that the existence of an infrared fixed point
with $g_1,g_2\neq 0$, which does not exhibit symmetry enhancement, does not
generally lead to any obvious unitarity violations or other inconsistencies. We
do show, however, that the $F$-theorem excludes the models with $g_1,g_2\neq 0$
for $N>5$. The conformal bootstrap provides a stronger constraint and excludes
such models for $N>2$. We provide evidence that the $g_2=0$ models, which have
the enhanced $O(N)\times U(1)$ symmetry, come close to saturating the bootstrap
bounds. We extend our analysis to fractional dimensions where we can motivate
the nonexistence of the $g_1,g_2\neq 0$ models by studying them perturbatively
in the $4-\epsilon$ expansion.Comment: 26 pages, 5 figure
Pseudoscalar Portal Dark Matter and New Signatures of Vector-like
  Fermions

Fermionic dark matter interacting with the Standard Model sector through a
pseudoscalar portal could evade the direct detection constraints while
preserving a WIMP miracle. We study the LHC constraints on the pseudoscalar
production in simplified models with the pseudoscalar either dominantly coupled
to b quarks or tau leptons and explore their implications for the GeV excesses
in gamma ray observations. We also investigate models with new vector-like
fermions that could realize the simplified models of pseudoscalar portal dark
matter. These models yield new decay channels and signatures of vector-like
fermions, for instance, bbb, btautau, and tautautau resonances. Some of the
signatures have already been strongly constrained by the existing LHC searches
and the parameter space fitting the gamma ray excess is further restricted. On
the other hand, the pure tau-rich final state is only weakly constrained so far
due to the small electroweak production rate.Comment: 18 pages, 7 figures; references added, minor modifications and match
  the JHEP versio
The Amplituhedron and the One-loop Grassmannian Measure

All-loop planar scattering amplitudes in maximally supersymmetric Yang-Mills
theory can be formulated geometrically in terms of the "amplituhedron". We
study the mathematical structures of the one-loop amplituhedron, and present a
new formula for its canonical measure, or the one-loop Grassmannian measure
formula. Using the recently proposed momentum-twistor diagrams, we show that
there is a correspondence between the cells of one-loop amplituhedron, BCFW
terms or equivalently on-shell diagrams, and residues of the one-loop
Grassmannian formula. In particular, for the first non-trivial case of one-loop
NMHV, these structures are naturally associated with a nice geometric picture
as polygons in projective space, as we discuss in various illustrative
examples.Comment: 31+10 pages, many figure
Next-to-next-to-eikonal corrections in the CGC

We extend the study of corrections to the eikonal approximation that was
initiated in Ref. \cite{Altinoluk:2014oxa} to higher orders. These corrections
associated with the finite width of the target are investigated and the gluon
propagator in background field is calculated at next-to-next-to-eikonal
accuracy. The result is then applied to the single inclusive gluon production
cross section at central rapidities and the light-front helicity asymmetry, in
pA collisions, in order to analyse these observables beyond the eikonal limit.
The next-to-next-to-eikonal corrections to the unpolarized cross section are
non-zero and provide the first corrections to the usual $k_\perp$-factorized
expression. In contrast, the eikonal and next-to-next-to-eikonal contributions
to the helicity asymmetry vanish, while the next-to-eikonal ones are non-zero.Comment: 32 page
Classical limit of irregular blocks and Mathieu functions

The Nekrasov-Shatashvili limit of the N=2 SU(2) pure gauge (Omega-deformed)
super Yang-Mills theory encodes the information about the spectrum of the
Mathieu operator. On the other hand, the Mathieu equation emerges entirely
within the frame of two-dimensional conformal field theory (2d CFT) as the
classical limit of the null vector decoupling equation for some degenerate
irregular block. Therefore, it seems to be possible to investigate the spectrum
of the Mathieu operator employing the techniques of 2d CFT. To exploit this
strategy, a full correspondence between the Mathieu equation and its
realization within 2d CFT has to be established. In our previous paper [1], we
have found that the expression of the Mathieu eigenvalue given in terms of the
classical irregular block exactly coincides with the well known weak coupling
expansion of this eigenvalue in the case in which the auxiliary parameter is
the noninteger Floquet exponent. In the present work we verify that the formula
for the corresponding eigenfunction obtained from the irregular block
reproduces the so-called Mathieu exponent from which the noninteger order
elliptic cosine and sine functions may be constructed. The derivation of the
Mathieu equation within the formalism of 2d CFT is based on conjectures
concerning the asymptotic behaviour of irregular blocks in the classical limit.
A proof of these hypotheses is sketched. Finally, we speculate on how it could
be possible to use the methods of 2d CFT in order to get from the irregular
block the eigenvalues of the Mathieu operator in other regions of the coupling
constant.Comment: 41 pages, 1 figur
Group-theoretic restrictions on generation of CP-violation in
  multi-Higgs-doublet models

It has been known since decades that imposing a symmetry group G on the
scalar sector of multi-Higgs-doublet models has consequences for CP-violation.
In all examples of two- and three-Higgs-doublet models equipped with
symmetries, one observes the following intriguing property: if G prevents
explicit CP-violation (CPV), at least in the neutral Higgs sector, then it also
prevents spontaneous CPV, and if G allows explicit CPV, then it allows for
spontaneous CPV. One is led to conjecture that this is a general phenomenon. In
this paper, we prove this conjecture for any rephasing symmetry group G and any
number of doublets.Comment: 16 page
$\bar{B}\rightarrow D^{(\ast)}\tau \bar{\nu}$ excesses in ALRSM
  constrained from $B$, $D$ decays and $D^{0}-\bar{D}^{0}$ mixing

Recent experimental results from the LHCb, BaBar and Belle collaborations on
the semitauonic decays of $B$ meson, $\bar{B}\rightarrow D^{(\ast)}\tau
\bar{\nu}$, showing a significant deviation from the Standard Model (SM), hint
towards a new physics scenario beyond the SM. In this work, we show that these
enhanced decay rates can be explained within the framework of $E_{6}$ motivated
Alternative Left-Right Symmetric Model (ALRSM), which has been successful in
explaining the recent CMS excesses and has the feature of accommodating high
scale leptogenesis. The R-parity conserving couplings in ALRSM can contribute
universally to both $\bar{B}\rightarrow D \tau \bar{\nu}$ and
$\bar{B}\rightarrow D^{(\ast)}\tau \bar{\nu}$ via the exchange of scalar
leptoquarks. We study the leptonic decays $D_{s}^{+} \rightarrow \tau^{+}
\bar{\nu}$, $B^{+}\rightarrow \tau^{+} \bar{\nu}$, $D^{+}\rightarrow \tau^{+}
\bar{\nu}$ and $D^{0}$-$\bar{D}^{0}$ mixing to constrain the couplings involved
in explaining the enhanced $B$ decay rates and we find that ALRSM can explain
the current experimental data on $\mathcal{R}(D^{(\ast)})$ quite well while
satisfying these constraints.Comment: 10 pages, 10 figures, minor refinements, all results unchanged, new
  references adde
Direct and indirect signals of natural composite Higgs models

We present a comprehensive numerical analysis of a four-dimensional model
with the Higgs as a composite pseudo-Nambu-Goldstone boson that features a
calculable Higgs potential and protective custodial and flavour symmetries to
reduce electroweak fine-tuning. We employ a novel numerical technique that
allows us for the first time to study constraints from radiative electroweak
symmetry breaking, Higgs physics, electroweak precision tests, flavour physics,
and direct LHC bounds on fermion and vector boson resonances in a single
framework. We consider four different flavour symmetries in the composite
sector, one of which we show to not be viable anymore in view of strong
precision constraints. In the other cases, all constraints can be passed with a
sub-percent electroweak fine-tuning. The models can explain the excesses
recently observed in $WW$, $WZ$, $Wh$ and $\ell^+\ell^-$ resonance searches by
ATLAS and CMS and the anomalies in angular observables and branching ratios of
rare semi-leptonic $B$ decays observed by LHCb. Solving the $B$ physics
anomalies predicts the presence of a dijet or $t\bar t$ resonance around 1 TeV
just below the sensitivity of LHC run 1. We discuss the prospects to probe the
models at run 2 of the LHC. As a side product, we identify several gaps in the
searches for vector-like quarks at hadron colliders, that could be closed by
reanalyzing existing LHC data.Comment: 74 pages, 21 figures. v2: references added, discussion in 3.2.6
  extende
Searches of exotic Higgs bosons in general mass spectra of the
  Georgi-Machacek model at the LHC

We derive the most general sets of viable mass spectra of the exotic Higgs
bosons in the Georgi-Machacek model that are consistent with the theoretical
constraints of vacuum stability and perturbative unitarity and the experimental
constraints of electroweak precision observables, $Zb \bar b$ coupling and
Higgs boson signal strengths. Branching ratios of various cascade decay
channels of the doubly-charged Higgs boson in the ${\bf 5}$ representation, the
singly-charged Higgs boson in ${\bf 3}$, and the singlet Higgs boson are
further computed. As one of the most promising channels for discovering the
model, we study the prospects for detecting the doubly-charged Higgs boson that
is produced via the vector boson fusion process and decays into final states
containing a pair of same-sign leptons at the 14-TeV LHC and a 100-TeV future
$pp$ collider. For this purpose, we evaluate acceptance times efficiency for
signals of the doubly-charged Higgs boson with general viable mass spectra and
compare it with the standard model background estimates.Comment: Version accepted for publication in JHE
Fermion mass without symmetry breaking

We examine a model of reduced staggered fermions in three dimensions
interacting through an $SO(4)$ invariant four fermion interaction. The model is
similar to that considered in a recent paper by Ayyer and Chandrasekharan
\cite{Ayyar:2014eua}. We present theoretical arguments and numerical evidence
which support the idea that the system develops a mass gap for sufficiently
strong four fermi coupling.{\it without} producing a symmetry breaking fermion
bilinear condensate. Massless and massive phases appear to be separated by a
continuous phase transition.Comment: 20 pages, 13 figures. New figures. Version accepted for publication
  in JHE
Wormholes, Emergent Gauge Fields, and the Weak Gravity Conjecture

This paper revisits the question of reconstructing bulk gauge fields as
boundary operators in AdS/CFT. In the presence of the wormhole dual to the
thermofield double state of two CFTs, the existence of bulk gauge fields is in
some tension with the microscopic tensor factorization of the Hilbert space. I
explain how this tension can be resolved by splitting the gauge field into
charged constituents, and I argue that this leads to a new argument for the
"principle of completeness", which states that the charge lattice of a gauge
theory coupled to gravity must be fully populated. I also claim that it leads
to a new motivation for (and a clarification of) the "weak gravity conjecture",
which I interpret as a strengthening of this principle. This setup gives a
simple example of a situation where describing low-energy bulk physics in CFT
language requires knowledge of high-energy bulk physics. This contradicts to
some extent the notion of "effective conformal field theory", but in fact is an
expected feature of the resolution of the black hole information problem. An
analogous factorization issue exists also for the gravitational field, and I
comment on several of its implications for reconstructing black hole interiors
and the emergence of spacetime more generally.Comment: 26 pages plus appendices, 8 figures. v2: minor
  clarifications/corrections, references adde
Effective theories of universal theories

It is well-known but sometimes overlooked that constraints on the oblique
parameters (most notably $S$ and $T$ parameters) are generally speaking only
applicable to a special class of new physics scenarios known as universal
theories. In the effective field theory (EFT) framework, the oblique parameters
should not be associated with Wilson coefficients in a particular operator
basis, unless restrictions have been imposed on the EFT so that it describes
universal theories. We work out these restrictions, and present a detailed EFT
analysis of universal theories. We find that at the dimension-6 level,
universal theories are completely characterized by 16 parameters. They are
conveniently chosen to be: 5 oblique parameters that agree with the
commonly-adopted ones, 4 anomalous triple-gauge couplings, 3 rescaling factors
for the $h^3$, $hff$, $hVV$ vertices, 3 parameters for $hVV$ vertices absent in
the Standard Model, and 1 four-fermion coupling of order $y_f^2$. All these
parameters are defined in an unambiguous and basis-independent way, allowing
for consistent constraints on the universal theories parameter space from
precision electroweak and Higgs data.Comment: 40 pages + appendix and references, 8 table
Sterile neutrinos in the light of IceCube

We determine constraints on parameters of a single eV-scale light neutrino
using IceCube-59 data. Particular emphasis is put on the question whether such
an analysis can rule out sterile neutrino hints. While important complementary
information is provided, the different dependence on the various sterile
neutrino mixing angles makes it currently not possible to fully exclude short
baseline appearance results or sterile neutrinos in general.Comment: Typos corrected, some comments and references added. Accepted by JHE
Brane solutions sourced by a scalar with vanishing potential and
  classification of scalar branes

We derive exact brane solutions of minimally coupled Einstein-Maxwell-scalar
gravity in d+2 dimensions with a vanishing scalar potential. The solutions are
conformal to the Lifshitz spacetime and have several properties, which make
them interesting for holographic applications. In particular, the dual QFT is
characterized by hyperscaling violation. We show that our solutions, together
with the AdS brane and the domain wall sourced by an exponential potential,
give the complete list of scalar branes sourced by a generic potential having
simple (scale-covariant) scaling symmetries. This allows us to give a complete
classification of both simple and interpolating brane solution of minimally
coupled Einstein-Maxwell-scalar gravity, which may be very useful for
holographic applications.Comment: 12 pages, no figure
Observations on fluxes near anti-branes

We revisit necessary conditions for gluing local (anti-)D3 throats into flux
throats with opposite charge. These consistency conditions typically reveal
singularities in the three-form fluxes whose meaning is being debated. In this
note we prove, under well-motivated assumptions, that unphysical singularities
can potentially be avoided when the anti-branes polarise into spherical NS5
branes with a specific radius. If a consistent solution can then indeed be
found, our analysis seems to suggests a rather large correction to the radius
of the polarization sphere compared to the probe result. We furthermore comment
on the gluing conditions at finite temperature and point out that one specific
assumption of a recent no-go theorem can be broken if anti-branes are indeed to
polarise into spherical NS5 branes at zero temperature.Comment: 17 pages, 2 figures, v2: error corrected and text extende