Dynamics and the gauge/gravity duality

De snaartheorie is de laatste jaren meer en meer een volwaardige tak van onderzoek geworden binnen de theoretische natuurkunde. Een belangrijke doorbraak in de snaartheorie was een concrete implementatie van het zogeheten holografisch principe. In essentie dicteert dit principe dat één dimensie van de ruimtetijd eigenlijk overbodig is in onze beschrijving ervan, net zoals een hologram een driedimensionaal beeld vastlegt op een plat vlak. Hoe dit ‘vergeten' van een dimensie in detail werkt was echter tot dusver alleen duidelijk in evenwichtssituaties. Balt van Rees ontwikkelde in detail de consequenties van het holografisch principe voor niet-evenwichtssituaties. Uiteindelijk moet dit leiden tot een holografische beschrijving van dynamische verschijnselen zoals de explosie van een ster of de vorming van een zwart gat

Conformal invariance in the long-range Ising model

We consider the question of conformal invariance of the long-range Ising model at the critical point. The continuum description is given in terms of a nonlocal field theory, and the absence of a stress tensor invalidates all of the standard arguments for the enhancement of scale invariance to conformal invariance. We however show that several correlation functions, computed to second order in the epsilon expansion, are nontrivially consistent with conformal invariance. We proceed to give a proof of conformal invariance to all orders in the epsilon expansion, based on the description of the long-range Ising model as a defect theory in an auxiliary higher-dimensional space. A detailed review of conformal invariance in the d-dimensional short-range Ising model is also included and may be of independent interest

The N=2 superconformal bootstrap

In this work we initiate the conformal bootstrap program for N=2N=2 super-conformal field theories in four dimensions. We promote an abstract operator-algebraic viewpoint in order to unify the description of Lagrangian and non-Lagrangian theories, and formulate various conjectures concerning the landscape of theories. We analyze in detail the four-point functions of flavor symmetry current multiplets and of N=2N=2 chiral operators. For both correlation functions we review the solution of the superconformal Ward identities and describe their superconformal block decompositions. This provides the foundation for an extensive numerical analysis discussed in the second half of the paper. We find a large number of constraints for operator dimensions, OPE coefficients, and central charges that must hold for any N=2N=2 superconformal field theory

Prediction of adenomyosis diagnosis based on MRI

ObjectiveDevelopment of a multivariate prediction model based on MRI and clinical parameters for histological adenomyosis diagnosis.Materials and methodsThis single centre retrospective cohort study took place in the gynaecological department of a referral hospital. In all, 296 women undergoing hysterectomy with preoperative pelvic MRI between 2007–2022 were included. MRI scans were retrospectively assessed for adenomyosis markers (junctional zone [JZ] parameters, high signal intensity [HSI] foci in a blinded fashion. A multivariate regression model for histopathological adenomyosis diagnosis was developed based on MRI and clinical variables from univariate analysis with p < 0.1 and factors deemed clinically relevant.Results131/296 women (44.3%) had histopathological adenomyosis. Patients had comparable age at hysterectomy, BMI and clinical symptoms, p > 0.05. Adenomyosis patients more often had: undergone a curettage (22.1% vs. 8.9%, p = 0.002), a higher mean JZ thickness (9.40 vs. 8.35 mm, p < .001), maximal JZ thickness (16.00 vs. 13.40 mm, p < .001), mean JZ/myometrium ratio (0.56 vs. 0.49, p = .040), and JZ differential (8.60 vs. 8.15 mm, p = .003). Presence of HSI foci was the strongest predictor for adenomyosis (39.7% vs. 8.9%, p < .001). Based on the parameters age and BMI, history of curettage, dysmenorrhoea, abnormal uterine bleeding (AUB), mean JZ, JZ differential ≥ 5 mm, JZ/myometrium ratio > 40, and presence of HSI foci, a predictive model was created with a good area under the curve (AUC) of .776.ConclusionsThis is the first study to create a diagnostic tool based on MRI and clinical parameters for adenomyosis diagnosis. After sufficient external validation, this model could function as a useful clinical decision-making tool in women with suspected adenomyosis

The influence of uterine abnormalities on uterine peristalsis in the non-pregnant uterus:A systematic review

Uterine peristalsis is the rhythmic wave-like motion of the subendometrial layer of the uterus. These contractions change throughout the menstrual cycle in terms of direction, frequency and amplitude, and can be analysed with various methods. Not much is known about uterine peristalsis in patients with uterine abnormalities. To that end, we decided to systematically review the available studies for evidence on the influence of uterine abnormalities, including leiomyomas, endometriosis, adenomyosis and congenital uterine anomalies, on uterine peristalsis. After a systematic search of relevant databases, sixteen eligible studies were included in this review; eight case-control studies and eight controlled prospective cohort studies. The sample sizes ranged from twelve to 205 participants. Various methods of analysing uterine contractions were used, including transvaginal ultrasound, hysterosalpingo-radionuclide scintigraphy, cine MRI and intrauterine pressure measurement. Studies varied in their design, uterine contraction measurement method and patient groups. Generally however, uterine abnormalities do seem to have an influence on uterine peristalsis. Compared to healthy controls, the specific phase of the menstrual cycle (namely the periovulatory and luteal phases) seems to play a major role in the observed effect on uterine contractions. The included studies were difficult to compare directly due to heterogeneity however, and sample sizes were relatively small. Despite these limitations, it can be concluded that uterine abnormalities likely have a menstrual phase-dependent effect on uterine peristalsis and contraction features. These aberrant contractions potentially play a role in the relationship between (benign) uterine abnormalities and infertility, along with other associated symptoms (i.e., dysmenorrhea, abnormal uterine bleeding). It is not yet possible to make a definite conclusion on the nature of this effect however. Further research is needed on objective measurement tools, treatment and clinical consequences of abnormal uterine peristalsis in patients with uterine abnormalities

Real-time gauge/gravity duality: Prescription, Renormalization and Examples

We present a comprehensive analysis of the prescription we recently put forward for the computation of real-time correlation functions using gauge/gravity duality. The prescription is valid for any holographic supergravity background and it naturally maps initial and final data in the bulk to initial and final states or density matrices in the field theory. We show in detail how the technique of holographic renormalization can be applied in this setting and we provide numerous illustrative examples, including the computation of time-ordered, Wightman and retarded 2-point functions in Poincare and global coordinates, thermal correlators and higher-point functions.Comment: 85 pages, 13 figures; v2: added comments and reference