This is partly because the mathematics in this field is highly complicated. At the same time, it is tough to perform suitable experiments: One would have to create situations in which phenomena of both the relativity theory play an important role, for example, a spacetime curved by heavy masses, and at the same time, quantum effects become visible, for example the dual particle and wave nature of light.

At the TU Wien in Vienna, Austria, a new approach has now been developed for this purpose: A so-called “quantum simulator” is used to get to the bottom of such questions: Instead of directly investigating the system of interest (namely quantum particles in curved spacetime), one creates a “model system” from which one can then learn something about the system of actual interest by analogy. The researchers have now shown that this quantum simulator works excellently. The findings of this international collaboration involving physicists from the University of Crete, Nanyang Technological University, and FU Berlin are now published in the scientific journal Proceedings of the National Academy of Sciences of the USA (PNAS).

Learning from one system about another

The basic idea behind the quantum simulator is simple: Many physical systems are similar. Even if they are entirely different kinds of particles or physical systems on different scales that, at first glance, have little to do with each other, these systems may obey the same laws and equations at a deeper level. This means one can learn something about a particular system by studying another.

“We take a quantum system that we know we can control and adjust very well in experiments,” says Prof. Jörg Schmiedmayer of the Atomic Institute at TU Wien. “In our case, these are ultracold atomic clouds held and manipulated by an atom chip with electromagnetic fields.” Suppose you properly adjust these atomic clouds so that their properties can be translated into another quantum system. In that case, you can learn something about the other system from the measurement of the atomic cloud model system — much like you can learn something about the oscillation of a pendulum from the oscillation of a mass attached to a metal spring: They are two different physical systems, but one can be translated into the other.

The gravitational lensing effect

“We have now been able to show that we can produce effects in this way that can be used to resemble the curvature of spacetime,” says Mohammadamin Tajik of the Vienna Center for Quantum Science and Technology (VCQ) — TU Wien, first author of the current paper. In the vacuum, light propagates along a so-called “light cone.” The speed of light is constant; at equal times, the light travels the same distance in each direction. However, if the light is influenced by heavy masses, such as the sun’s gravitation, these light cones are bent. The light’s paths are no longer perfectly straight in curved spacetimes. This is called “gravitational lens effect.”

The same can now be shown in atomic clouds. Instead of the speed of light, one examines the speed of sound. “Now we have a system in which there is an effect that corresponds to spacetime curvature or gravitational lensing, but at the same time, it is a quantum system that you can describe with quantum field theories,” says Mohammadamin Tajik. “With this, we have a completely new tool to study the connection between relativity and quantum theory.”

A model system for quantum gravity

The experiments show that the shape of light cones, lensing effects, reflections, and other phenomena can be demonstrated in these atomic clouds precisely as expected in relativistic cosmic systems. This is not only interesting for generating new data for basic theoretical research — solid-state physics and the search for new materials also encounter questions that have a similar structure and can therefore be answered by such experiments.

“We now want to control these atomic clouds better to determine even more far-reaching data. For example, interactions between the particles can still be changed in a very targeted way,” explains Jörg Schmiedmayer. In this way, the quantum simulator can recreate physical situations that are so complicated that they cannot be calculated even with supercomputers.

The quantum simulator thus becomes a new, additional source of information for quantum research — in addition to theoretical calculations, computer simulations, and direct experiments. When studying the atomic clouds, the research team hopes to come across new phenomena that may have been entirely unknown up to now, which also take place on a cosmic, relativistic scale — but without a look at tiny particles, they might never have been discovered.

New research led by the University of Oxford has found that climate change is causing the hottest days in North-West Europe to warm at double the rate of average summer days. The difference in trends is most pronounced for England, Wales, and Northern France. Worryingly, while current climate models accurately predict the rate of warming for average days, they underestimate the rate at which the hottest days are warming compared to observations.

According to lead researcher Dr Matthew Patterson, from the University of Oxford’s Department of Physics, the results indicate that extreme heat events — such as the UK’s record-breaking heatwave last summer — are likely to become more regular. Dr Patterson said: ‘These findings underline the fact that the UK and neighbouring countries are already experiencing the effects of climate change, and that last year’s heatwave was not a fluke. Policy makers urgently need to adapt their infrastructure and health systems to cope with the impacts of higher temperatures.’

For the study, published today in Geographical Research Letters, Dr Patterson analysed data from the past 60 years (1960-2021) recording the maximum daily temperature, provided by the European Centre for Medium-Range Weather Forecasts.

Although the maximum recorded temperature varied between years, the overall trend clearly showed that the hottest days for North-West Europe had warmed at twice the rate of average summer days. For England and Wales, the average summer day increased by approximately 0.26°C per decade, whilst the hottest day increased by around 0.58°C per decade. However, this faster warming of the hottest days was not observed to this extent elsewhere in the Northern Hemisphere.

The reason causing this faster warming of the hottest days relative to average summer days is not yet understood. According to Dr Patterson, this may be due to the hottest summer days in North-West Europe often being linked to hot air transported north from over Spain. Because Spain is warming faster than North-West Europe, this means that air carried in from this region is ever more extreme relative to the ambient air in North-West Europe. The hottest days of 2022, for instance, were driven by a plume of hot air carried north from Spain and the Sahara. However, further research is needed to verify this.

Dr Patterson added: ‘Understanding the warming rate of the hottest days will be important if we are to improve climate model simulation of extreme events and make accurate predictions about the future intensity of such events. If our models underestimate the rise in extreme temperatures over the coming decades, we will underestimate the impacts this will have.’

Extreme heat has significant negative impacts on many different aspects of society, including energy and transport infrastructure, and agriculture. It also exacerbates conditions including respiratory and cardiovascular diseases, putting a strain on health services.

The current UK Government has been criticised by the Climate Change Committee (CCC) for failing to act quickly enough to adapt for the impacts of global heating. These new findings add even more urgency for policy makers to adapt infrastructure and systems vulnerable to extreme heat.

The study, which was the first to test an AI voice-based virtual coach for behavioral therapy, found changes in patients’ brain activity along with improved depression and anxiety symptoms after using Lumen, an AI voice assistant that delivered a form of psychotherapy.

The UIC team says the results, which are published in the journal Translational Psychiatry, offer encouraging evidence that virtual therapy can play a role in filling the gaps in mental health care, where waitlists and disparities in access are often hurdles that patients, particularly from vulnerable communities, must overcome to receive treatment.

“We’ve had an incredible explosion of need, especially in the wake of COVID, with soaring rates of anxiety and depression and not enough practitioners,” said Dr. Olusola A. Ajilore, UIC professor of psychiatry and co-first author of the paper. “This kind of technology may serve as a bridge. It’s not meant to be a replacement for traditional therapy, but it may be an important stop-gap before somebody can seek treatment.”

Lumen, which operates as a skill in the Amazon Alexa application, was developed by Ajilore and study senior author Dr.Jun Ma, the Beth and George Vitoux Professor of Medicine at UIC, along with collaborators at Washington University in St. Louis and Pennsylvania State University, with the support of a $2 million grant from the National Institute of Mental Health.

The UIC researchers recruited over 60 patients for the clinical study exploring the application’s effect on mild-to-moderate depression and anxiety symptoms, and activity in brain areas previously shown to be associated with the benefits of problem-solving therapy.

Two-thirds of the patients used Lumen on a study-provided iPad for eight problem-solving therapy sessions, with the rest serving as a “waitlist” control receiving no intervention.

After the intervention, study participants using the Lumen app showed decreased scores for depression, anxiety and psychological distress compared with the control group. The Lumen group also showed improvements in problem-solving skills that correlated with increased activity in the dorsolateral prefrontal cortex, a brain area associated with cognitive control. Promising results for women and underrepresented populations also were found.

“It’s about changing the way people think about problems and how to address them, and not being emotionally overwhelmed,” Ma said. “It’s a pragmatic and patient-driven behavior therapy that’s well established, which makes it a good fit for delivery using voice-based technology.”

A larger trial comparing the use of Lumen with both a control group on a waitlist, and patients receiving human-coached problem-solving therapy is currently being conducted by the researcher. They stress that the virtual coach doesn’t need to perform better than a human therapist to fill a desperate need in the mental health system.

“The way we should think about digital mental health service is not for these apps to replace humans, but rather to recognize what a gap we have between supply and demand, and then find novel, effective and safe ways to deliver treatments to individuals who otherwise do not have access, to fill that gap,” Ma said.

Co-first author of the study is Thomas Kannampallil at Washington University in St. Louis.

Other co-investigators include Aifeng Zhang, Nan Lv, Nancy E. Wittels, Corina R. Ronneberg, Vikas Kumar, Susanth Dosala, Amruta Barve, Kevin C. Tan, Kevin K. Cao, Charmi R. Patel and Emily A. Kringle, all of UIC; Joshua Smyth and Jillian A. Johnson at Pennsylvania State University; and Lan Xiao at Stanford University.

Mimicking ants is a good defense option because they do not make for good eating; ants often have spiny defenses and biting mandibles (and they’re not afraid to fight back), and many also carry chemical repellants or venom. Though the focal spider of this study — Siler collingwoodi — was already known to move in an ant-like fashion, the researchers wanted to know how accurate its mimicry is, whether it mimics more than one ant species, and how effective this mimicry is at discouraging predators.

The research team also explored the role of the spider’s brilliant coloration. “Unlike typical ant-mimicking spiders that mimic the brown or black body color of ants, S. collingwoodi has brilliant body coloration,” says first author Hua Zeng, an ecologist at Peking University. “From a human’sperspective, it seems to blend well with plants in its environment, but we wanted to test whether their body coloration served as camouflage to protect against predators.”

To understand how ant-mimicry helps these spiders avoid being eaten, the researchers collected wild ant-mimicking spiders from four geographic locations in southern Hainan, China, and brought them back to the lab. For comparison, they also collected another type of jumping spider that doesn’t mimic ants, as well as five co-occurring ant species that they thought might serve as models.

Back in the lab, the researchers characterized and compared how the ants and spiders moved in terms of how they used individual limbs, as well as their speed, acceleration, and whether they followed a straight path or took a more tortuous trajectory.

They found that, rather than jumping like most jumping spiders, S. collingwoodi move like ants: by raising their front legs to mimic an ant’s antennae, bobbing their abdomens, and lifting their legs to walk in an ant-like manner. Of the five ant species, the spiders’ walking style most closely resembled the three smaller ant species, who are also closer to it in size.

“S. collingwoodi is not necessarily a perfect mimic, because its gait and trajectory showed high similarity with multiple ant species,” says Zeng. “Being a general mimic rather than perfectly mimicking one ant species could benefit the spiders by allowing them to expand their range if the ant models occupy different habitats.”

Next, the researchers tested the spider’s defenses against two likely predators: a similarly sized jumping spider with color vision that specializes in preying upon other spiders (Portia labiata) and a praying mantis (Gonypeta brunneri) that is a generalist predator with a monochromatic visual system.

To explore the role of color camouflage, the researchers modeled how the two predators would perceive S. collingwoodi relative to the other prey species against the background of two plants that the spiders live on — the red-flowering West Indian jasmine (Ixora chinensis) and the Fukien tea tree (Carmona microphylla). They found that the ant-mimicking spiders were better camouflaged from both spider and praying mantis predators on the jasmine plant than the tea tree plant.

When the predators were given the choice of the ant-mimicking spider and the other jumping spider, the predatory spider was more likely to attack the non-mimic; out of 17 trials, the spider launched 5 attacks, all of which were towards the non-mimic. Praying mantises, however, attacked both prey species with equal alacrity.

“We initially thought that both predators would behave similarly in the antipredation experiments, but in fact the simulated ant locomotion of Siler collingwoodi only worked for the jumping spider predator, while the praying mantis showed indiscriminate attacks on both ants and mimics,” says senior author Wei Zhang, an evolutionary ecologist at Peking University.

This difference might be driven by each predator’s likelihood of being injured from eating an ant. The praying mantises are much larger than their prey, so they can get away with eating spiny ants without risking grave injury, but this is not the case for the predatory spiders.

“For the spider predator, a random attack on an ant could result in injury, so they are very careful predators and will only attack if they can distinguish S. collingwoodi from ants with a high degree of certainty,” says Zhang.

However, losing a limb compromised the ant-mimicking spiders’ ability to avoid the predatory spider’s attention, probably by preventing them from accurately mimicking ants.