328 research outputs found
Inelastic decay from integrability
A hallmark of integrable systems is the purely elastic scattering of their
excitations. Such systems possess an extensive number of locally conserved
charges, leading to the conservation of the number of scattered excitations, as
well as their set of individual momenta. In this work, we show that inelastic
decay can nevertheless be observed in circuit QED realizations of integrable
boundary models. We consider the scattering of microwave photons off impurities
in superconducting circuits implementing the boundary sine-Gordon and Kondo
models, which are both integrable. We show that not only inelastic decay is
possible for the microwave photons, in spite of integrability, and thanks to a
nonlinear relation between them and the elastically-scattered excitations, but
also that integrability in fact provides powerful analytical tools allowing to
obtain exact expressions for response functions describing the inelastic decay.
Using the framework of form factors, we calculate the total inelastic decay
rate and elastic phase shift of the microwave photons, extracted from a 2-point
response function. We then go beyond linear response and obtain the exact
energy-resolved inelastic decay spectrum, using a novel method to evaluate form
factor expansions of 3-point response functions, which could prove useful in
other applications of integrable quantum field theories. We relate our results
to several recent photon splitting experiments, and in particular to recent
experimental data that provides evidence for the elusive Schmid-Bulgadaev
dissipative quantum phase transition.Comment: 36 pages, 5 figures. See also a paper by M. Houzet, T. Yamamoto and
L. I. Glazman on the same arXiv postin
Systematic Biases in LLM Simulations of Debates
Recent advancements in natural language processing, especially the emergence
of Large Language Models (LLMs), have opened exciting possibilities for
constructing computational simulations designed to replicate human behavior
accurately. However, LLMs are complex statistical learners without
straightforward deductive rules, making them prone to unexpected behaviors. In
this study, we highlight the limitations of LLMs in simulating human
interactions, particularly focusing on LLMs' ability to simulate political
debates. Our findings indicate a tendency for LLM agents to conform to the
model's inherent social biases despite being directed to debate from certain
political perspectives. This tendency results in behavioral patterns that seem
to deviate from well-established social dynamics among humans. We reinforce
these observations using an automatic self-fine-tuning method, which enables us
to manipulate the biases within the LLM and demonstrate that agents
subsequently align with the altered biases. These results underscore the need
for further research to develop methods that help agents overcome these biases,
a critical step toward creating more realistic simulations
Inelastic scattering of a photon by a quantum phase-slip
Spontaneous decay of a single photon is a notoriously inefficient process in
nature irrespective of the frequency range. We report that a quantum phase-slip
fluctuation in high-impedance superconducting waveguides can split a single
incident microwave photon into a large number of lower-energy photons with a
near unit probability. The underlying inelastic photon-photon interaction has
no analogs in non-linear optics. Instead, the measured decay rates are
explained without adjustable parameters in the framework of a new model of a
quantum impurity in a Luttinger liquid. Our result connects circuit quantum
electrodynamics to critical phenomena in two-dimensional boundary quantum field
theories, important in the physics of strongly-correlated systems. The photon
lifetime data represents a rare example of verified and useful quantum
many-body simulation.Comment: minor revision for clarity, supplementary material is available at
www.superconducting-circuits.co
Less is better than more with resection of periacetabular tumors – A retrospective 16 years study and literature review
IntroductionWide resections of periacetabular tumors create a sizeable bony defect that inevitably results in severe loss of function. Reconstruction of such defects usually requires using large metal implants, a feature associated with considerable surgery extension and complications. The aim of this study is to report resection with no reconstruction of the bony defect. In this retrospective study, we reviewed a consecutive series of 16 patients diagnosed with malignant periacetabular tumors and underwent en-bloc resection without reconstructing their remaining bone defect.MethodsRecords were reviewed of 16 consecutive patients diagnosed with malignant periacetabular tumors and underwent en-bloc resection without reconstructing their remaining bony defect. Measurements included: the duration of surgery, blood loss, hemoglobin levels and the need for blood transfusions, data on other hospitalization characteristics, and intraoperative and postoperative complications.ResultsSixteen patients with malignant periacetabular bone tumors and extensive bone destruction underwent wide periacetabular tumor resection with a mean follow-up of 75 months and a mean age of 53 years. The average HOOS score was 46 (range: 20 to 76), and the mean MSTS score was 13% (range: 0 to 15). The mean operative time was 4.1 h, and the mean blood loss was 1200 ml. At their most recent follow-up, patients had a mean shortening of their operated extremity of 4.8 cm, and all could ambulate with assisting devices.ConclusionWide resection of periacetabular tumors without reconstruction provides acceptable levels of function and was associated with shorter surgical time, less blood loss and fewer postoperative complications compared to resection with reconstruction. Therefore, this approach may be considered a viable surgical option in patients with an extensive malignant periacetabular.Level IIIRetrospective study
Characteristics associated with quality of life among people with drug-resistant epilepsy
Quality of Life (QoL) is the preferred outcome in non-pharmacological trials, but there is little UK population evidence of QoL in epilepsy. In advance of evaluating an epilepsy self-management course we aimed to describe, among UK participants, what clinical and psycho-social characteristics are associated with QoL. We recruited 404 adults attending specialist clinics, with at least two seizures in the prior year and measured their self-reported seizure frequency, co-morbidity, psychological distress, social characteristics, including self-mastery and stigma, and epilepsy-specific QoL (QOLIE-31-P). Mean age was 42 years, 54% were female, and 75% white. Median time since diagnosis was 18 years, and 69% experienced ≥10 seizures in the prior year. Nearly half (46%) reported additional medical or psychiatric conditions, 54% reported current anxiety and 28% reported current depression symptoms at borderline or case level, with 63% reporting felt stigma. While a maximum QOLIE-31-P score is 100, participants’ mean score was 66, with a wide range (25–99). In order of large to small magnitude: depression, low self-mastery, anxiety, felt stigma, a history of medical and psychiatric comorbidity, low self-reported medication adherence, and greater seizure frequency were associated with low QOLIE-31-P scores. Despite specialist care, UK people with epilepsy and persistent seizures experience low QoL. If QoL is the main outcome in epilepsy trials, developing and evaluating ways to reduce psychological and social disadvantage are likely to be of primary importance. Educational courses may not change QoL, but be one component supporting self-management for people with long-term conditions, like epilepsy
A Cookbook of Self-Supervised Learning
Self-supervised learning, dubbed the dark matter of intelligence, is a
promising path to advance machine learning. Yet, much like cooking, training
SSL methods is a delicate art with a high barrier to entry. While many
components are familiar, successfully training a SSL method involves a dizzying
set of choices from the pretext tasks to training hyper-parameters. Our goal is
to lower the barrier to entry into SSL research by laying the foundations and
latest SSL recipes in the style of a cookbook. We hope to empower the curious
researcher to navigate the terrain of methods, understand the role of the
various knobs, and gain the know-how required to explore how delicious SSL can
be
Inhibition of adenosine monophosphate-activated protein kinase-3-hydroxy-3-methylglutaryl coenzyme a reductase signaling leads to hypercholesterolemia and promotes hepatic steatosis and insulin resistance
Adenosine monophosphate–activated protein kinase (AMPK) regulates multiple signaling pathways involved in glucose and lipid metabolism in response to changes in hormonal and nutrient status. Cell culture studies have shown that AMPK phosphorylation and inhibition of the rate‐limiting enzyme in the mevalonate pathway 3‐hydroxy‐3‐methylglutaryl (HMG) coenzyme A (CoA) reductase (HMGCR) at serine‐871 (Ser871; human HMGCR Ser872) suppresses cholesterol synthesis. In order to evaluate the role of AMPK‐HMGCR signaling in vivo, we generated mice with a Ser871‐alanine (Ala) knock‐in mutation (HMGCR KI). Cholesterol synthesis was significantly suppressed in wild‐type (WT) but not in HMGCR KI hepatocytes in response to AMPK activators. Liver cholesterol synthesis and cholesterol levels were significantly up‐regulated in HMGCR KI mice. When fed a high‐carbohydrate diet, HMGCR KI mice had enhanced triglyceride synthesis and liver steatosis, resulting in impaired glucose homeostasis. Conclusion: AMPK‐HMGCR signaling alone is sufficient to regulate both cholesterol and triglyceride synthesis under conditions of a high‐carbohydrate diet. Our findings highlight the tight coupling between the mevalonate and fatty acid synthesis pathways as well as revealing a role of AMPK in suppressing the deleterious effects of a high‐carbohydrate diet
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A 680,000-person megastudy of nudges to encourage vaccination in pharmacies
Encouraging vaccination is a pressing policy problem. To assess whether text-based reminders can encourage pharmacy vaccination and what kinds of messages work best, we conducted a megastudy. We randomly assigned 689,693 Walmart pharmacy patients to receive one of 22 different text reminders using a variety of different behavioral science principles to nudge flu vaccination or to a business-as-usual control condition that received no messages. We found that the reminder texts that we tested increased pharmacy vaccination rates by an average of 2.0 percentage points, or 6.8%, over a 3-mo follow-up period. The most-effective messages reminded patients that a flu shot was waiting for them and delivered reminders on multiple days. The top-performing intervention included two texts delivered 3 d apart and communicated to patients that a vaccine was “waiting for you.” Neither experts nor lay people anticipated that this would be the best-performing treatment, underscoring the value of simultaneously testing many different nudges in a highly powered megastudy
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