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Tag: University of Cambridge

  • Can Cosmic Inflation Be Ruled Out?

    Can Cosmic Inflation Be Ruled Out?

    Newswise — Astrophysicists say that cosmic inflation – a point in the Universe’s infancy when space-time expanded exponentially, and what physicists really refer to when they talk about the ‘Big Bang’ – can in principle be ruled out in an assumption-free way.

    The astrophysicists, from the University of Cambridge, the University of Trento, and Harvard University, say that there is a clear, unambiguous signal in the cosmos which could eliminate inflation as a possibility. Their paper, published in The Astrophysical Journal Letters, argues that this signal – known as the cosmic graviton background (CGB) – can feasibly be detected, although it will be a massive technical and scientific challenge.

    “Inflation was theorised to explain various fine-tuning challenges of the so-called hot Big Bang model,” said the paper’s first author Dr Sunny Vagnozzi, from Cambridge’s Kavli Institute for Cosmology, and is now based at the University of Trento. “It also explains the origin of structure in our Universe as a result of quantum fluctuations.

    “However, the large flexibility displayed by possible models for cosmic inflation which span an unlimited landscape of cosmological outcomes raises concerns that cosmic inflation is not falsifiable, even if individual inflationary models can be ruled out. Is it possible in principle to test cosmic inflation in a model-independent way?”

    Some scientists raised concerns about cosmic inflation in 2013, when the Planck satellite released its first measurements of the cosmic microwave background (CMB), the universe’s oldest light.

    “When the results from the Planck satellite were announced, they were held up as a confirmation of cosmic inflation,” said Professor Avi Loeb from Harvard University, Vagnozzi’s co-author on the current paper. “However, some of us argued that the results might be showing just the opposite.”

    Along with Anna Ijjas and Paul Steinhardt, Loeb was one of those who argued that results from Planck showed that inflation posed more puzzles than it solved, and that it was time to consider new ideas about the beginnings of the universe, which, for instance. may have begun not with a bang but with a bounce from a previously contracting cosmos.

    The maps of the CMB released by Planck represent the earliest time in the universe we can ‘see’, 100 million years before the first stars formed. We cannot see farther.

    “The actual edge of the observable universe is at the distance that any signal could have travelled at the speed-of-light limit over the 13.8 billion years that elapsed since the birth of the Universe,” said Loeb. “As a result of the expansion of the universe, this edge is currently located 46.5 billion light years away. The spherical volume within this boundary is like an archaeological dig centred on us: the deeper we probe into it, the earlier is the layer of cosmic history that we uncover, all the way back to the Big Bang which represents our ultimate horizon. What lies beyond the horizon is unknown.”

    In could be possible to dig even further into the universe’s beginnings by studying near-weightless particles known as neutrinos, which are the most abundant particles that have mass in the universe. The Universe allows neutrinos to travel freely without scattering from approximately a second after the Big Bang, when the temperature was ten billion degrees. “The present-day universe must be filled with relic neutrinos from that time,” said Vagnozzi.

    Vagnozzi and Loeb say we can go even further back, however, by tracing gravitons, particles which mediate the force of gravity.

    “The Universe was transparent to gravitons all the way back to the earliest instant traced by known physics, the Planck time: 10 to the power of -43 seconds, when the temperature was the highest conceivable: 10 to the power of 32 degrees,” said Loeb. “A proper understanding of what came before that requires a predictive theory of quantum gravity, which we do not possess.”

    Vagnozzi and Loeb say that once the Universe allowed gravitons to travel freely without scattering, a relic background of thermal gravitational radiation with a temperature of slightly less than one degree above absolute zero should have been generated: the cosmic graviton background (CGB).

    However, the Big Bang theory does not allow for the existence of the CGB, as it suggests that the exponential inflation of the newborn universe diluted relics such as the CGB to a point that they are undetectable. This can be turned into a test: if the CGB were detected, clearly this would rule out cosmic inflation, which does not allow for its existence.

    Vagnozzi and Loeb argue that such a test is possible, and the CGB could in principle be detected in future. The CGB adds to the cosmic radiation budget, which otherwise includes microwave and neutrino backgrounds. It therefore affects the cosmic expansion rate of the early Universe at a level that is detectable by next-generation cosmological probes, which could provide the first indirect detection of the CGB.

    However, to claim a definitive detection of the CGB, the ‘smoking gun’ would be the detection of a background of high-frequency gravitational waves peaking at frequencies around 100 GHz. This would be very hard to detect, and would require tremendous technological advances in gyrotron and superconducting magnets technology. Nevertheless, say the researchers, this signal may be within our reach in future.

    University of Cambridge

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  • UK policing: Psychological damage among officers heightened by bad working conditions – study

    UK policing: Psychological damage among officers heightened by bad working conditions – study

    Newswise — High levels of trauma-related mental health disorders across UK police forces are partly the result of bad working conditions such as having too little time, sexual harassment, and dealing with difficult situations without support, according to a study led by the University of Cambridge. 

    However, officers who say they feel supported by colleagues, and have a sense of doing meaningful work, had around half the rates of a form of PTSD as the national average for policing staff.

    Researchers behind the study say their findings suggest that simple improvements to the working lives of police – scheduled time for support from peers and supervisors, for example – could dramatically reduce the level of psychiatric problems in UK forces. 

    Sociologists surveyed thousands of police personnel across the country in 2018 and found that 12% showed clinical symptoms of Complex Post-Traumatic Stress Disorder (C-PTSD), a chronic condition in which repeated trauma exposure causes social disconnection, feelings of worthlessness, and an inability to regulate emotions.

    Complex PTSD often leads to “burnout” and substance abuse. In fact, 90% of police workers in the original survey study ‘The Job, The Life’ had experienced trauma, and one in five of these reported symptoms of either PTSD or C-PTSD.

    Now, the same team of researchers have analysed survey data provided by 12,248 serving police officers to determine the working conditions and on-the-job situations with the strongest links to Complex PTSD. The latest findings are published in the journal Policing.

    Trauma detailed by officers with probable levels of Complex PTSD based on the survey screening included dealing with fatal car accidents, rapes, homicides, suicides – including of children – and drug overdoses.  

    Exposure to physical violence made little difference to rates of C-PTSD, nor did long working hours.

    However, officers who described it as “very difficult” to take time away from the job for personal or family matters had C-PTSD rates over 50% higher than the UK-wide average for police.  

    Those who described their relationship between work and personal life as “not fitting well at all”, some 15% of police officers in the study, had twice (24%) the average policing rates of C-PTSD.  

    One officer suffering with probable C-PTSD described how what you see “impacts on your life outside of work”, offering the example of cases involving dead children that “make you anxious about your own children’s wellbeing. To a degree you lose your innocence.”    

    Another C-PTSD sufferer said “it is a given and accepted” that the job means exposure to trauma, and describes the occupational health team in their force as “brilliant” but few in number. “They are only able to put ‘sticky plasters’ on, and send the officers back out,” the officer said.

    Police officers who described never having enough time to “get the job done” had almost double the rates of C-PTSD as the average across UK forces, 22% compared to 12%, as did officers who reported experiencing sexual harassment – whether from the public or colleagues*.    

    Officers who said they could never rely on the help and support of colleagues were most likely to suffer with Complex PTSD, with over 43% displaying symptoms, but such claims were relatively rare.

    One detective with C-PTSD symptoms recounted dealing with sexual abuse cases as the sole investigating officer. “Little or no support from management. Victims hanging all their hopes and pressures on me.”

    By contrast, C-PTSD rates were just 7% among those who said they could always rely on colleagues, and just 6% among those who say they regularly get a feeling of a job well done, with researchers claiming that a sense of meaningful work may provide a “protective effect” mentally.   

    “Our research shows that the debilitating psychological misery often caused by trauma exposure isn’t an inevitable part of the difficult job of policing, it is exacerbated by poor working conditions,” said Prof Brendan Burchell, lead author from Cambridge’s Department of Sociology.     

    The team also conducted analyses beyond individual officers to compare forces, revealing a strong link between “work intensity” – those forces with more officers reporting a lack of time to effectively police – and increased rates of Complex PTSD.

    Of 18 anonymised UK police forces, the one with the highest reported time constraints among officers had C-PTSD rates of 29%, well over double the average for the overall policing population.

    “Severe austerity cuts since 2010 leading to a marked reduction in police numbers without a decrease in the demands of the job inevitably creates more time pressure for remaining officers,” said Burchell.

    “Single-crewing, shift work and fewer resources mean that time for encouraging words between colleagues or space for officers to acknowledge their traumatic experiences are few and far between.”

    One officer with probable C-PTSD described being “single crewed” at a rural location for a year, with nearest support almost an hour away. Another spoke of going from a shift team of five to working alone. “My coping strategy of being around colleagues who had been to the same fatal accident or suicide was taken away from me.”  

    Cambridge co-author Dr Jessica Miller, who is also director of research for Police Care UK, the charity that funded the research, added: “The police forces reporting the best working conditions had much lower rates of PTSD. Modest investments to improve their working conditions could see significant reductions in psychological problems among police officers.”

     

    University of Cambridge

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  • Students in Rwanda confound pandemic predictions and head back to school

    Students in Rwanda confound pandemic predictions and head back to school

    Newswise — New data from Rwanda, and some of the first published on how COVID-19 has impacted school attendance in the Global South, suggest that a widely-predicted spike in drop-out rates has “not materialised”.

    Ever since the pandemic forced schools around the world to close, analysts, academics and teachers have been warning that many students in poorer countries might not return. According to some estimates, more than 10 million school-age students are at risk of dropping out worldwide. There have been particular concerns about marginalised groups such as the very poorest children and girls.

    The new study, which used enrolment data from 358 Rwandan secondary schools, collected both before and after the closures, found that rather than undergoing a sharp fall, student numbers actually rose when schools reopened. The cause appears to have been a combination of existing students returning, and the enrolment of other pupils who were out of school before the pandemic began.

    Researchers say that this may represent an emerging trend, because as-yet unpublished results from other sub-Saharan countries, such as Ethiopia and Malawi, similarly show no steep fall in numbers.

    Despite this, a more gradual, long-term decline in the numbers of children in school may be underway. The research tracked enrolment past the point where schools reopened in Rwanda, and up to May 2021. By that stage, some students did appear to be dropping out of the system. This was particularly true of those from marginalised groups.

    The research was undertaken by a team from the University of Cambridge and the East African research and data collection firm, Laterite, and was carried out for the Mastercard Foundation’s Leaders in Teaching Initiative.

    Professor Pauline Rose, Director of the Research for Equitable Access and Learning (REAL) Centre, at the Faculty of Education, University of Cambridge, said: “Given the seriousness of the impact of COVID-19, I wouldn’t have been surprised if enrolment rates had halved when schools reopened. We are still developing a comprehensive picture of the situation across Sub-Saharan Africa, but the impact on drop-outs appears far less extreme than initially feared.”

    “It is important we continue to monitor the situation. There was clearly real enthusiasm for schools to reopen at first, but there are now signs that some children may potentially be disappearing from the system.”

    Schools in Rwanda closed in March 2020 and did not reopen until November, when they did so on a staggered basis. The research collected aggregate enrolment data from before the pandemic, in February 2020, and a year later, in February 2021.

    This showed that after schools reopened, enrolment rates rose in the Secondary 1 and Secondary 4 year groups: natural entry points into the Rwandan system because they mark the start of lower and upper secondary school respectively. Enrolment rose by 7% at the Secondary 1 level, and 11% at Secondary 4, in February 2021. Numbers remained steady in the other year groups.

    Crucially, the Rwanda Basic Education Board decided to make all students return to the year group that they were previously in when schools reopened. This means that the Secondary 1 and 4 year groups comprised the same cohorts across 2020 and 2021. The rise in numbers was therefore almost certainly due to students who had previously dropped out re-joining their cohort in February 2021.

    The study also gathered both enrolment and assessment data from a sample of 2,800 students in the Secondary 3 year group, which it followed up to May 2021.

    By that stage, researchers found, some students had started to drop out. About 89% of the entire sample group were still in school by May 2021, but the figure was lower among girls, and particularly among students who were over the ‘expected’ cohort age because they had been kept back an additional year or more. The overage group were also disproportionately likely to come from less-wealthy backgrounds.

    “Keeping track of these children is really important,” Mico Rudasingwa, Research Associate at Laterite said. “By the time they reach adolescence, those from the poorest backgrounds in particular are in danger of dropping out early to support with income generating activities for the household.”

    The sample group of students also took a learning assessment, in the form of a numeracy test, in February 2020, and again in May 2021 – two terms after their return to school. The results were measured using a ‘latent ability score’ – given as a figure between 0 and 1 – which takes into account not only how many questions they got right, but how difficult those questions were. The average score rose from 0.47 in the first test to 0.52 in the second. Over 90% of the schools in the sample group recorded an average improvement in numeracy scores.

    Although positive, these results should be treated with caution, as there is no counterfactual evidence available about how much their test results might have improved had the school closures never occurred. The learning levels of some groups also improved more than others. Boys generally outperformed girls by about 0.02 points on the latent ability scale, while overage students again lagged behind their peers, by about 0.03 points.

    The study also collected teacher retention data by tracking 1,700 teachers in science, technology, engineering and maths (STEM) subjects before and after the closures. Around 94% of STEM teachers returned to their classes in early 2021, and almost half the schools surveyed saw an overall increase in STEM teachers through new recruitment. The report describes this low turnover rate as ‘encouraging’.

    The full report is available on the REAL Centre website.

    University of Cambridge

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