981 research outputs found
New BPS Wilson loops in circular quiver Chern-Simons-matter theories
We construct new families of 1/4 BPS Wilson loops in circular quiver
superconformal Chern-Simons-matter (SCSM) theories in three
dimensions. They are defined as the holonomy of superconnections that contain
non-trivial couplings to scalar and fermions, and cannot be reduced to
block-diagonal matrices. Consequently, the new operators cannot be written in
terms of double-node Wilson loops, as the ones considered so far in the
literature. For particular values of the couplings the superconnection becomes
block-diagonal and we recover the known fermionic 1/4 and 1/2 BPS Wilson loops.
The new operators are cohomologically equivalent to bosonic 1/4 BPS Wilson
loops and are then amenable of exact evaluation via localization techniques.
Moreover, in the case of orbifold ABJM theory we identify the corresponding
gravity duals for some of the 1/4 and 1/2 BPS Wilson loops.Comment: 32 pages; v2: minor improvements, general classification of BPS WLs
added; v3: comments added, typos fixed, JHEP published versio
String theory duals of Wilson loops from Higgsing
For three-dimensional ABJ(M) theories and Chern-Simons-matter
quiver theories, we construct two sets of 1/2 BPS Wilson loop operators by
applying the Higgsing procedure along independent directions of the moduli
space, and choosing different massive modes. For theories whose dual M-theory
description is known, we also determine the corresponding spectrum of 1/2 BPS
M2-brane solutions. We identify the supercharges in M-theory and field theory,
as well as the supercharges preserved by M2-/anti-M2-branes and 1/2 BPS Wilson
loops. In particular, in orbifold ABJM theory we find pairs of
different 1/2 BPS Wilson loops that preserve exactly the same set of
supercharges. In field theory they arise by Higgsing with the choice of either
particles or antiparticles, whereas in the dual description they correspond to
a pair of M2-/anti-M2-branes localized at different positions in the compact
space. This result enlightens the origin of classical Wilson loop degeneracy in
these theories, already discussed in arXiv:1506.07614. A discussion on possible
scenarios that emerge by comparison with localization results is included.Comment: 52 pages, 4 figures; V2, 61 pages, 4 figures, supercharges in gravity
and field theory identified, conclusion unchanged, published versio
The Economics of Producing Grafted Coffee Plants
Eighty-five percent of the land planted with coffee in Kona is infested with the Kona coffee root-knot nematode, Meloidogyne konaensis. Nematodes even in low numbers are very damaging to coffee tree roots, and it is estimated that infested farms are losing about 60 percent of their yield potential. Nematicides are relatively ineffective in the soil conditions of Kona. CTAHR researchers have recommended use of a nematode-resistant rootstock known as Coffea dewevrei. The cost of producing field-ready grafted coffee nursery stock is calculated using an economic model of the production process. Understanding the cost of producing grafted plants will help producers determine whether it is more cost-effective to purchase grafted nursery stock or to produce their own grafted plants, or whether it is profitable to produce grafted coffee plants for sale to other coffee growers
Probing Wilson loops in Chern-Simons-matter theories at weak coupling
For three-dimensional super Chern-Simons-matter theories
associated to necklace quivers , we study at quantum level the two kinds of 1/2 BPS Wilson loop operators
recently introduced in arXiv:1506.07614. We perform a two-loop evaluation and
find the same result for the two kinds of operators, so moving to higher loops
a possible quantum uplift of the classical degeneracy. We also compute the 1/4
BPS bosonic Wilson loop and discuss the quantum version of the cohomological
equivalence between fermionic and bosonic Wilson loops. We compare the
perturbative result with the Matrix Model prediction and find perfect matching,
after identification and remotion of a suitable framing factor. Finally, we
discuss the potential appearance of three-loop contributions that might break
the classical degeneracy and briefly analyse possible implications on the BPS
nature of these operators.Comment: 7 pages, 2 figure
A matrix model for the latitude Wilson loop in ABJM theory
In ABJ(M) theory, we propose a matrix model for the exact evaluation of BPS
Wilson loops on a latitude circular contour, so providing a new weak-strong
interpolation tool. Intriguingly, the matrix model turns out to be a particular
case of that computing torus knot invariants in Chern-Simons
theory. At weak coupling we check our proposal against a three-loop
computation, performed for generic framing, winding number and representation.
The matrix model is amenable of a Fermi gas formulation, which we use to
systematically compute the strong coupling and genus expansions. For the
fermionic Wilson loop the leading planar behavior agrees with a previous string
theory prediction. For the bosonic operator our result provides a clue for
finding the corresponding string dual configuration. Our matrix model is
consistent with recent proposals for computing Bremsstrahlung functions exactly
in terms of latitude Wilson loops. As a by-product, we extend the conjecture
for the exact Bremsstrahlung function to generic
representations and test it with a four-loop perturbative computation. Finally,
we propose an exact prediction for at unequal gauge group ranks.Comment: 73 pages; v2: several improvements, JHEP published versio
Towards the exact Bremsstrahlung function of ABJM theory
We present the three-loop calculation of the Bremsstrahlung function
associated to the 1/2-BPS cusp in ABJM theory, including color subleading
corrections. Using the BPS condition we reduce the computation to that of a
cusp with vanishing angle. We work within the framework of heavy quark
effective theory (HQET) that further simplifies the analytic evaluation of the
relevant cusp anomalous dimension in the near-BPS limit. The result passes
nontrivial tests, such as exponentiation, and is in agreement with the
conjecture made in [1] for the exact expression of the Bremsstrahlung function,
based on the relation with fermionic latitude Wilson loops.Comment: 46 pages, 15 figure
The quantum 1/2 BPS Wilson loop in Chern-Simons-matter theories
In three dimensional Chern-Simons-matter theories two
independent fermionic Wilson loop operators can be defined, which preserve half
of the supersymmetry charges and are cohomologically equivalent at classical
level. We compute their three-loop expectation value in a convenient color
sector and prove that the degeneracy is uplifted by quantum corrections. We
expand the matrix model prediction in the same regime and by comparison we
conclude that the quantum 1/2 BPS Wilson loop is the average of the two
operators. We provide an all-loop argument to support this claim at any order.
As a by-product, we identify the localization result at three loops as a
correction to the framing factor induced by matter interactions. Finally, we
comment on the quantum properties of the non-1/2 BPS Wilson loop operator
defined as the difference of the two fermionic ones.Comment: 22 pages + appendixes, 4 figures, 1 Tabl
The Bremsstrahlung function of SCQCD
For superconformal QCD we perform a three-loop calculation of the
generalized cusp anomalous dimension of the BPS Wilson loop operator using HQET
formalism. We obtain an expression which is valid at generic geometric and
internal angles and finite gauge group rank . For equal and opposite angles
this expression vanishes, proving that at these points the cusp becomes BPS.
From its small angle expansion we derive the corresponding Bremsstrahlung
function at three loops, matching the matrix model prediction given in terms of
derivatives of the Wilson loop on the ellipsoid. Finally, we discuss possible
scenarios at higher loops, with respect to the existence of a universal
effective coupling in an integrable subsector of the model.Comment: 30 pages; v3: JHEP published versio
MOF-Derived CeO2 and CeZrOx Solid Solutions: Exploring Ce Reduction through FTIR and NEXAFS Spectroscopy
The development of Ce-based materials is directly dependent on the catalyst surface defects, which is caused by the calcination steps required to increase structural stability. At the same time, the evaluation of ceriumâs redox properties under reaction conditions is of increasing relevant importance. The synthesis of Ce-UiO-66 and CeZr-UiO-66 and their subsequent calcination are presented here as a simple and inexpensive approach for achieving homogeneous and stable CeO2 and CeZrOx nanocrystals. The resulting materials constitute an ideal case study to thoroughly understand cerium redox properties. The Ce3+/Ce4+ redox properties are investigated by H2-TPR experiments exploited by in situ FT-IR and Ce M5-edge AP-NEXAFS spectroscopy. In the latter case, Ce3+ formation is quantified using the MCR-ALS protocol. FT-IR is then presented as a high potential/easily accessible technique for extracting valuable information about the cerium oxidation state under operating conditions. The dependence of the OH stretching vibration frequency on temperature and Ce reduction is described, providing a novel tool for qualitative monitoring of surface oxygen vacancy formation. Based on the reported results, the molecular absorption coefficient of the Ce3+ characteristic IR transition is tentatively evaluated, thus providing a basis for future Ce3+ quantification through FT-IR spectroscopy. Finally, the FT-IR limitations for Ce3+ quantification are discussed
Analysis of professional perceptions relating to the effectiveness of codes of ethics for journalists in Spain
The methodology used in the present study is based on quantitative content analysis using the survey technique. This technique makes it possible to obtain empirical data on various key aspects of the profession that are determining factors in ascertaining Spanish journalistsâ views of one of the instruments of accountability that is external to the media: general ethical codes.
The results show that Spanish journalists are largely confident in the effectiveness of ethical codes in their profession. Likewise, it was seen that variables such as age, professional experience or the media with which they work influence the perceptions that professionals have of such instruments.
If we understand journalism as a profession whose mission is to guarantee the citizenship their right to information, it is essential to be familiar with the tools provided by the profession itself in order to be accountable to the public regarding this professional mission. Hence the importance of instruments of accountability and the perceptions of the professionals themselves regarding their effectiveness
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