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On September 14th and December 26th, 2015, the Advanced LIGO detectors observed two gravitational wave signals, each from the merger of stellar-mass black holes. The LIGO Scientific Collaboration's search, based on general-relativistic models of gravitational wave signals from binary black hole systems, identified these two signals, GW150914 and GW151226, with a significance greater than 5 sigma over the observational period. In this talk I will discuss these first detections of gravitational waves, describe how we measured these signals and estimated their significance, and how we ruled out all possible causes of these signals except binary black holes. I will also discuss the future of the exciting new field of gravitational-wave astronomy.
Event Time
15:00-16:00
Venue
Elizabeth Livingston LT
Speaker
Dr Laura Nuttall
Cosmological perturbation theory is currently a preferred mathematical procedure to compare the equations of gravity with precise observations. However, due to the difficulties in interpreting gauge-invariance and invertibility in Hamiltonian formalism, there is no consistent and generalized Hamiltonian analysis for cosmological perturbation theory at any order for any kind of model of gravity. In this work, using a simple model, we provide a simple mathematical approach to deal with all the difficulties to obtain a consistent Hamiltonian formalism and extend the approach to canonical scalar field. We show that our approach can be applied to any order of perturbation for any first order derivative fields. We also apply our approach to Galilean scalar field model and show that, there is no extra degrees of freedom, as expected, at every order of perturbation and obtain all consistent equations of motion. We compare and contrast our approach to the Lagrangian approach (Chen et al [2006]) for extracting higher order correlations and show that our approach is quick and robust and can be applied to any model of gravity and matter fields without invoking slow-roll approximation. This approach can not only be used for higher order correlation but can also be used to obtain mixed-mode correlation functions at any level of perturbations. Finally, by introducing a new phase-space variable, we show that the approach can also be easily extended to generalized non-canonical scalar field and it leads to a new definition of speed of sound in phase-space.
Event Time
14:00-15:00
Venue
Management School Lecture Theatre 5
Speaker
Debottam Nandi, Ph.D. student at School of Physics, IISER-TVM, Trivandrum, India
Dr Adam Noble, University of Strathclyde
Event Time
1.30pm-2.30pm
Venue
Furness LT 1
Speaker
Dr Adam Noble, University of Strathclyde
The advent of spacetime cloaking in 2011 opened a new paradigm in transformation optics in which the full spacetime covariance of Maxwell's equations was exploited to design, theoretically, a dynamic medium capable of concealing events. Shortly afterwards spacetime cloaks were demonstrated experimentally in systems that exploited dispersion in optical fibres. Somewhat ironically, dispersion was neglected in the original proposal of spacetime cloaking, and a theoretical apparatus that properly accounts for dispersion has only recently been established. I will describe the historical evolution towards the spacetime cloak, how it was demonstrated experimentally, and some of the new theoretical challenges in transformation optics it poses.
Event Time
3pm-4pm
Venue
Furness LT 1
Speaker
Prof. Martin McCall, Imperial College, London
<August 2016>
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Day | Week | Month | Year | Upcoming