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ECHO, ECHo, Echo, echo... When echoes overwhelm Landau damping

Series
Oxford Physics Public Lectures
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Physics Colloquium 6th May 2016 delivered by Professor William Dorland

The Liouville equation describing a collection of charged particles is time-reversible. In the weakly coupled limit, one can reduce this equation to a Fokker-Planck equation, which is irreversible. The problem of the fate of electromagnetic field fluctuations in a plasma in the limit of very weak irreversibility was addressed by Landau, who demonstrated that as long as there are some collisions (even if very rare), and in the absence of sources, gradients, etc, typical field fluctuations are damped with an easily calculated “collisionless” damping rate -- this is Landau damping. The energy of the field fluctuations is converted to particle energy; there is irreversible heating. Landau’s calculation is fine in the limit of small amplitude fluctuations, but what happens when the plasma is turbulent? I will show that in a typical nonlinear system (relevant to many physical observations), Landau damping is overwhelmed and ultimately arrested by turbulent “echoes”. This finding has important implications for detailed predictions of the heating (and in some cases, for the luminosity) of some interesting astrophysical plasmas.

Episode Information

Series
Oxford Physics Public Lectures
People
William Dorland
Keywords
liouville equation
charged particles
electromagnetic field fluctuations
plasma
landau
Department: Department of Physics
Date Added: 11/05/2016
Duration:

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Our Place in the Cosmos

Series
The Physics of Fine-Tuning
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Astrophysicist and bestselling author Mario Livio delivers a speculative talk about humans place in the cosmos.

Episode Information

Series
The Physics of Fine-Tuning
People
Mario Livio
Keywords
Physics
astronomy
fine-tuning
solar system
Department: Department of Physics
Date Added: 10/05/2016
Duration: 00:41:14

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Capitalizing on diversity: Outcomes of planet formation as initial conditions for life

Series
The Physics of Fine-Tuning
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Michael R. Meyer, Institute for Astronomy, Department of Physics, ETH Zurich, delivers a talk about planet formation and conditions for life to exist.

Episode Information

Series
The Physics of Fine-Tuning
People
Michael Meyer
Keywords
Physics
fine-tuning
exoplanets
astronomy
Department: Department of Physics
Date Added: 10/05/2016
Duration: 00:36:00

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Where and how might we search for life? From planet demographics to biosignatures

Series
The Physics of Fine-Tuning
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Professor Suzanne Aigrain is an expert exoplanet researcher. In this talk she will outline the methods for detection and characterisation of exoplanets in the context of finding planets that might harbor life.

Episode Information

Series
The Physics of Fine-Tuning
People
Suzanne Aigrain
Keywords
Physics
fine-tuning
exoplanets
life
cosmology
astronomy
Department: Department of Physics
Date Added: 10/05/2016
Duration: 00:43:34

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Emigration and the distribution of income per natural: Evidence from Egypt

Series
International Migration Institute
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Joachim Jarreau investigates whether the benefits of migration actually reach the poorest households
We study the impact of emigration on income distribution of Egyptian households, using longitudinal data covering 1998–2012. Controlling for selection of migrants and work participation of non-migrants, we find that remittances tend to increase income inequality at origin. However taking into account income earned abroad by migrants, adjusted for PPP differences, yields larger gains from migration and a negative impact on inequality of ‘income per natural’. We study the dependence of this effect with the saving share of migrants’ earnings. Positive selection of migrants tends to make migration inequality-increasing, while low transferability of skills in destination countries, primarily in the Gulf region, has the opposite effect. We argue that a focus on remittances is too restrictive to account for the whole benefits of migration to origin households, when transfer costs are high. We confirm this with household panel regressions showing that migration episodes have a significant and large impact in the medium-term on household permanent income, controlling for pre-departure characteristics. The medium-term benefits from migration have an inequality-reducing effect in particular in rural areas.
Creative Commons Licence
Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK (BY-NC-SA): England & Wales; https://creativecommons.org/licenses/by-nc-sa/2.0/uk/

Episode Information

Series
International Migration Institute
People
Joachim Jarreau
Keywords
inequality
household income
migration
migrant labour
egypt
poverty measurement
Department: Oxford Department of International Development
Date Added: 09/05/2016
Duration: 00:40:20

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The Not So Odd Couple: Richard Nixon and Daniel Patrick Moynihan

Series
Rothermere American Institute
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Mr Price, who joined the staff of the Nixon administration in 1969, working in the Urban Affairs Council, discusses the relationship between Moynihan and Nixon during the Nixon presidency.

Episode Information

Series
Rothermere American Institute
People
John Price
Keywords
Nixon
American Politics
moynihan
welfare
urban affairs
Department: Rothermere American Institute
Date Added: 09/05/2016
Duration: 00:50:00

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Truth and Reality in a Hyper-Connected World

Series
Women of Achievement
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Katharine Viner, the editor-in-chief at The Guardian, delivers the second Women of Achievement Lecture. Drawing on recent high profile news stories, Ms Viner highlights how truth is a troubling concept in todays modern era of journalism.

Episode Information

Series
Women of Achievement
People
Katharine Viner
Keywords
journalism
diversity
media
communications
Department: University Administration and Services (UAS)
Date Added: 09/05/2016
Duration: 01:11:44

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Women of Achievement

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This series is unique in being wholly dedicated to female speakers. It is intended to showcase the enormous range of women's careers and raise the profile of women of high achievement in order to increase the range of role models accessible to challenge and inspire women both at Oxford and outside. The lecture series is funded by the Vice Chancellor's Diversity Fund.

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How English Became English

Series
TORCH | The Oxford Research Centre in the Humanities
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A Book at Lunchtime discussion looking at the English language and how it is developing with Simon Horobin, Faramerz Dabhoiwala, Martin Wynne, Philip Durkin and Susie Dent.
The English Language is spoken by more than a billion people throughout the world. But where did English come from? And how has it evolved into the language used today?

Simon Horobin (Professor of English Language and Literature, University of Oxford) explores these questions with Faramerz Dabhoiwala (Associate Professor of Modern History, University of Oxford), Martin Wynne (Digital Methods Specialist, Oxford e-Research Centre, University of Oxford) and Philip Durkin (Deputy Chief Editor, Oxford English Dictionary) in a discussion centered around his new book 'How English Became English'.

The discussion is chaired by Susie Dent (English lexicographer and etymologist. Host of Countdown's "Dictionary Corner") and touches on topics as wide-ranging as cultural imperialism, snobbery, bullet points, Shakespeare, toilet brushes and alphabetti spaghetti.

Episode Information

Series
TORCH | The Oxford Research Centre in the Humanities
People
Simon Horobin
Faramerz Dabhoiwala
Martin Wynne
Philip Durkin
Susie Dent.
Keywords
literature
torch
language
english
linguistics
Department: The Oxford Research Centre in the Humanities (TORCH)
Date Added: 06/05/2016
Duration: 00:45:40

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The Future of the BBC

Series
Reuters Institute for the Study of Journalism
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Special lecture by former Chairman of the BBC Trust and current Chancellor of the University of Oxford Lord Patten of Barnes on the future of the BBC. Followed by a discussion between Lord Patten and Tim Gardam, Principal of St Anne's College.
The current BBC Charter expires at the end of 2016. Negotiations are underway for its renewal. A White Paper containing the British Government’s specific proposals for the future of the BBC is expected to be published this Summer.

Episode Information

Series
Reuters Institute for the Study of Journalism
People
Lord Patten of Barnes
Tim Gardam
Keywords
bbc
television
news
journalism
politics
internet
Department: Department of Politics and International Relations (DPIR)
Date Added: 05/05/2016
Duration: 01:05:22

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