A Quantum Window Onto Early Inflation

Inflation in the early Universe is one of the most promising probes of gravity in the high-energy regime. However, observable scales give access to a limited window in the inflationary dynamics. In this essay, we argue that quantum corrections to the classical dynamics of cosmological fields allow us to probe much earlier epochs of the inflationary phase and extend this window by many orders of magnitude. We point out that both the statistics of cosmological fluctuations at observable scales, and the field displacements acquired by spectator fields that play an important role in many post-inflationary processes, are sensitive to a much longer phase of the inflationary epoch.Comment: 5 pages, 2 figures. Honourable Mention from the Gravity Research Foundation 2017 Awards for Essays on Gravitation. Version to appear in October 2017 Special Issue of the International Journal of Modern Physics D. Updated to match the published versio

Network-Based Vertex Dissolution

We introduce a graph-theoretic vertex dissolution model that applies to a number of redistribution scenarios such as gerrymandering in political districting or work balancing in an online situation. The central aspect of our model is the deletion of certain vertices and the redistribution of their load to neighboring vertices in a completely balanced way. We investigate how the underlying graph structure, the knowledge of which vertices should be deleted, and the relation between old and new vertex loads influence the computational complexity of the underlying graph problems. Our results establish a clear borderline between tractable and intractable cases.Comment: Version accepted at SIAM Journal on Discrete Mathematic

A comparison of mean winds and gravity wave activity in the northern and southern polar MLT

Mean winds and waves observed in the mesosphere and lower thermosphere with MF radars located at Davis (69°S, 78°E) and Poker Flat (65°N, 147°W) are compared. Measurements covering the period from 1999 to mid 2000 show differences in the strength of the horizontal wind fields. In the southern hemisphere the zonal and meridional winds reach their maximum values near the summer solstice, but are delayed by 2–3 weeks in the northern hemisphere. Gravity wave variances also show significant differences, as do the strength of vertical velocities.Andrew Dowdy and Robert A. Vincent, Kiyoshi Igarashi and Yasuhiro Murayama, Damian J. Murph

A quantum trampoline for ultra-cold atoms

We have observed the interferometric suspension of a free-falling Bose-Einstein condensate periodically submitted to multiple-order diffraction by a vertical 1D standing wave. The various diffracted matter waves recombine coherently, resulting in high contrast interference in the number of atoms detected at constant height. For long suspension times, multiple-wave interference is revealed through a sharpening of the fringes. We use this scheme to measure the acceleration of gravity

Left ear advantage in speech-related dichotic listening is not specific to auditory processing disorder in children: A machine-learning fMRI and DTI study

AbstractDichotic listening (DL) tests are among the most frequently included in batteries for the diagnosis of auditory processing disorders (APD) in children. A finding of atypical left ear advantage (LEA) for speech-related stimuli is often taken by clinical audiologists as an indicator for APD. However, the precise etiology of ear advantage in DL tests has been a source of debate for decades. It is uncertain whether a finding of LEA is truly indicative of a sensory processing deficit such as APD, or whether attentional or other supramodal factors may also influence ear advantage. Multivariate machine learning was used on diffusion tensor imaging (DTI) and functional MRI (fMRI) data from a cohort of children ages 7–14 referred for APD testing with LEA, and typical controls with right-ear advantage (REA). LEA was predicted by: increased axial diffusivity in the left internal capsule (sublenticular region), and decreased functional activation in the left frontal eye fields (BA 8) during words presented diotically as compared to words presented dichotically, compared to children with right-ear advantage (REA). These results indicate that both sensory and attentional deficits may be predictive of LEA, and thus a finding of LEA, while possibly due to sensory factors, is not a specific indicator of APD as it may stem from a supramodal etiology

Levels of developmental assets and educational outcomes in young people in transitional living in Canada

"Developmental assets may be defined as significant relationships, skills, opportunities or values that protect young people in the presence of risk and promote their resilience. The purpose of this study was to discover whether high, medium, and low levels of developmental assets among transition-age young people in care were related to selected educational outcomes. If so, child welfare staff could potentially use their knowledge of a youth's level of assets to plan an appropriate level of educational assistance that would enable the youth to be more successful in his or her transition. The sample was composed of 567 young people (322 females and 245 males), aged 18-20 years, who were residing in a transitional living program in Ontario, Canada. The three levels of developmental assets were found to have statistically significant relationships with the seven educational outcomes examined that ranged between small-to-medium and strong in size. The educational outcomes consisted of the educational level in which the youth was currently enrolled, the highest educational level attained, average marks in school, participation in volunteering, employment, education or training, development of skills useful for employment, and adequacy of planning for the youth's education. The implications of the findings for rendering educational assistance to youths in particular need were discussed." (author's abstract)"Entwicklungsressourcen können als signifikante Beziehungen, Fähigkeiten, Chancen und Werte bestimmt werden, die Jugendliche in Risikolagen schützen und ihre Belastbarkeit fördern. Im Mittelpunkt der vorliegenden Studie stand die Frage, ob hohe, mittlere und niedrige Entwicklungsressourcenniveaus betreuter Jugendlicher in der Übergangsphase mit ausgewählten Bildungserfolgen in Zusammenhang stehen. Ist dies der Fall, könnten Fachkräfte ihr Wissen um die Entwicklungsressourcen von Jugendlichen nutzen, um eine angemessene pädagogische Begleitung zu planen, die Jugendlichen hilft, den Übergang erfolgreicher zu gestalten. Die Stichprobe der Studie setzte sich aus 567 jungen Menschen (322 Mädchen und 245 Jungen) im Alter von 18-20 Jahren zusammen, die ein Übergangsprogramm in Ontario (Kanada) durchliefen. Die Ergebnisse der Untersuchung zeigen, dass die drei Niveaus in unterschiedlicher Stärke statistisch signifikant mit Erfolgen in den sieben untersuchten Bildungsbereichen korrelieren. Diese umfassten den momentan angestrebten Bildungsabschluss, den höchsten bereits erreichten Bildungsabschluss, den Notendurchschnitt in der Schule, Partizipation in freiwilligen Engagements, Arbeit/ Beschäftigung, Bildung oder Training, die Entwicklung beschäftigungsrelevanter Fähigkeiten, sowie zukunftsorientierte Bildungspläne. Abschließend werden Folgerungen für die Begleitung von Jugendlichen mit spezifischen Bedürfnissen diskutiert." (Autorenreferat