859 research outputs found
Limit Cycles and Conformal Invariance
There is a widely held belief that conformal field theories (CFTs) require
zero beta functions. Nevertheless, the work of Jack and Osborn implies that the
beta functions are not actually the quantites that decide conformality, but
until recently no such behavior had been exhibited. Our recent work has led to
the discovery of CFTs with nonzero beta functions, more precisely CFTs that
live on recurrent trajectories, e.g., limit cycles, of the beta-function vector
field. To demonstrate this we study the S function of Jack and Osborn. We use
Weyl consistency conditions to show that it vanishes at fixed points and agrees
with the generator Q of limit cycles on them. Moreover, we compute S to third
order in perturbation theory, and explicitly verify that it agrees with our
previous determinations of Q. A byproduct of our analysis is that, in
perturbation theory, unitarity and scale invariance imply conformal invariance
in four-dimensional quantum field theories. Finally, we study some properties
of these new, "cyclic" CFTs, and point out that the a-theorem still governs the
asymptotic behavior of renormalization-group flows.Comment: 31 pages, 4 figures. Expanded introduction to make clear that cycles
discussed in this work are not associated with unitary theories that are
scale but not conformally invarian
Limit Cycles in Four Dimensions
We present an example of a limit cycle, i.e., a recurrent flow-line of the
beta-function vector field, in a unitary four-dimensional gauge theory. We thus
prove that beta functions of four-dimensional gauge theories do not produce
gradient flows. The limit cycle is established in perturbation theory with a
three-loop calculation which we describe in detail.Comment: 12 pages, 1 figure. Significant revision of the interpretation of our
result. Improved description of three-loop calculatio
Scale without Conformal Invariance at Three Loops
We carry out a three-loop computation that establishes the existence of scale
without conformal invariance in dimensional regularization with the MS scheme
in d=4-epsilon spacetime dimensions. We also comment on the effects of scheme
changes in theories with many couplings, as well as in theories that live on
non-conformal scale-invariant renormalization group trajectories. Stability
properties of such trajectories are analyzed, revealing both attractive and
repulsive directions in a specific example. We explain how our results are in
accord with those of Jack & Osborn on a c-theorem in d=4 (and d=4-epsilon)
dimensions. Finally, we point out that limit cycles with turning points are
unlike limit cycles with continuous scale invariance.Comment: 21 pages, 3 figures, Erratum adde
Recognition without identification, erroneous familiarity, and déjà vu
Déjà vu is characterized by the recognition of a situation concurrent with the awareness that this recognition is inappropriate. Although forms of déjà vu resolve in favor of the inappropriate recognition and therefore have behavioral consequences, typical déjà vu experiences resolve in favor of the awareness that the sensation of recognition is inappropriate. The resultant lack of behavioral modification associated with typical déjà vu means that clinicians and experimenters rely heavily on self-report when observing the experience. In this review, we focus on recent déjà vu research. We consider issues facing neuropsychological, neuroscientific, and cognitive experimental frameworks attempting to explore and experimentally generate the experience. In doing this, we suggest the need for more experimentation and amore cautious interpretation of research findings, particularly as many techniques being used to explore déjà vu are in the early stages of development.PostprintPeer reviewe
Decreased gastric emptying and gastrointestinal and intestinal transits of liquid after complete spinal cord transection in awake rats
Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016.
OBJECTIVE: To provide an update to "Surviving Sepsis Campaign Guidelines for Management of Sepsis and Septic Shock: 2012." DESIGN: A consensus committee of 55 international experts representing 25 international organizations was convened. Nominal groups were assembled at key international meetings (for those committee members attending the conference). A formal conflict-of-interest (COI) policy was developed at the onset of the process and enforced throughout. A stand-alone meeting was held for all panel members in December 2015. Teleconferences and electronic-based discussion among subgroups and among the entire committee served as an integral part of the development. METHODS: The panel consisted of five sections: hemodynamics, infection, adjunctive therapies, metabolic, and ventilation. Population, intervention, comparison, and outcomes (PICO) questions were reviewed and updated as needed, and evidence profiles were generated. Each subgroup generated a list of questions, searched for best available evidence, and then followed the principles of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system to assess the quality of evidence from high to very low, and to formulate recommendations as strong or weak, or best practice statement when applicable. RESULTS: The Surviving Sepsis Guideline panel provided 93 statements on early management and resuscitation of patients with sepsis or septic shock. Overall, 32 were strong recommendations, 39 were weak recommendations, and 18 were best-practice statements. No recommendation was provided for four questions. CONCLUSIONS: Substantial agreement exists among a large cohort of international experts regarding many strong recommendations for the best care of patients with sepsis. Although a significant number of aspects of care have relatively weak support, evidence-based recommendations regarding the acute management of sepsis and septic shock are the foundation of improved outcomes for these critically ill patients with high mortality
Superconformal Flavor Simplified
A simple explanation of the flavor hierarchies can arise if matter fields
interact with a conformal sector and different generations have different
anomalous dimensions under the CFT. However, in the original study by Nelson
and Strassler many supersymmetric models of this type were considered to be
'incalculable' because the R-charges were not sufficiently constrained by the
superpotential. We point out that nearly all such models are calculable with
the use of a-maximization. Utilizing this, we construct the simplest
vector-like flavor models and discuss their viability. A significant constraint
on these models comes from requiring that the visible gauge couplings remain
perturbative throughout the conformal window needed to generate the
hierarchies. However, we find that there is a small class of simple flavor
models that can evade this bound.Comment: 43 pages, 1 figure; V3: small corrections and clarifications,
references adde
Holographic c-theorems in arbitrary dimensions
We re-examine holographic versions of the c-theorem and entanglement entropy
in the context of higher curvature gravity and the AdS/CFT correspondence. We
select the gravity theories by tuning the gravitational couplings to eliminate
non-unitary operators in the boundary theory and demonstrate that all of these
theories obey a holographic c-theorem. In cases where the dual CFT is
even-dimensional, we show that the quantity that flows is the central charge
associated with the A-type trace anomaly. Here, unlike in conventional
holographic constructions with Einstein gravity, we are able to distinguish
this quantity from other central charges or the leading coefficient in the
entropy density of a thermal bath. In general, we are also able to identify
this quantity with the coefficient of a universal contribution to the
entanglement entropy in a particular construction. Our results suggest that
these coefficients appearing in entanglement entropy play the role of central
charges in odd-dimensional CFT's. We conjecture a new c-theorem on the space of
odd-dimensional field theories, which extends Cardy's proposal for even
dimensions. Beyond holography, we were able to show that for any
even-dimensional CFT, the universal coefficient appearing the entanglement
entropy which we calculate is precisely the A-type central charge.Comment: 62 pages, 4 figures, few typo's correcte
Framework, principles and recommendations for utilising participatory methodologies in the co-creation and evaluation of public health interventions
Background:
Due to the chronic disease burden on society, there is a need for preventive public health interventions to stimulate society towards a healthier lifestyle. To deal with the complex variability between individual lifestyles and settings, collaborating with end-users to develop interventions tailored to their unique circumstances has been suggested as a potential way to improve effectiveness and adherence. Co-creation of public health interventions using participatory methodologies has shown promise but lacks a framework to make this process systematic. The aim of this paper was to identify and set key principles and recommendations for systematically applying participatory methodologies to co-create and evaluate public health interventions.
Methods:
These principles and recommendations were derived using an iterative reflection process, combining key learning from published literature in addition to critical reflection on three case studies conducted by research groups in three European institutions, all of whom have expertise in co-creating public health interventions using different participatory methodologies.
Results:
Key principles and recommendations for using participatory methodologies in public health intervention co-creation are presented for the stages of: Planning (framing the aim of the study and identifying the appropriate sampling strategy); Conducting (defining the procedure, in addition to manifesting ownership); Evaluating (the process and the effectiveness) and Reporting (providing guidelines to report the findings). Three scaling models are proposed to demonstrate how to scale locally developed interventions to a population level.
Conclusions:
These recommendations aim to facilitate public health intervention co-creation and evaluation utilising participatory methodologies by ensuring the process is systematic and reproducible
Comments on Holographic Entanglement Entropy and RG Flows
Using holographic entanglement entropy for strip geometry, we construct a
candidate for a c-function in arbitrary dimensions. For holographic theories
dual to Einstein gravity, this c-function is shown to decrease monotonically
along RG flows. A sufficient condition required for this monotonic flow is that
the stress tensor of the matter fields driving the holographic RG flow must
satisfy the null energy condition over the holographic surface used to
calculate the entanglement entropy. In the case where the bulk theory is
described by Gauss-Bonnet gravity, the latter condition alone is not sufficient
to establish the monotonic flow of the c-function. We also observe that for
certain holographic RG flows, the entanglement entropy undergoes a 'phase
transition' as the size of the system grows and as a result, evolution of the
c-function may exhibit a discontinuous drop.Comment: References adde
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