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Contents contributed and discussions participated by Tessa Baker

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Cosmic Censorship: Formation of a Shielding Horizon Around a Fragile Horizon - 0 views

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    The Cosmic Censorship hypothesis suggests that gravitational singularities will always be hidden from the view of an external observer by an event horizon. It's sometimes given the status of a 'fundamental principle of the universe', though there's no particularly solid reasoning behind this (as far as I'm aware, at least). This short paper explores a gedanken experiment that attempts to violate cosmic censorship.
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What if Planck's Universe isn't flat? - 0 views

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    I'll let Phil do the talking on this one!
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A practical approach to cosmological perturbations in modified gravity - 0 views

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    There's been a growing awareness that the 'free' functions used to parameterise modified gravity aren't really as arbitrary as one might first think. This methods paper suggests how to use these ideas - although the forecast isn't all that encouraging. Still, the proof of the pudding is yet to come.
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Tickling the CMB damping tail: scrutinizing the tension between the ACT and SPT experim... - 0 views

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    Perhaps an ACT team member could give us a verdict on this?
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[1207.4543] The Atacama Cosmology Telescope: Cross-Correlation of CMB Lensing and Quasars - 1 views

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    Maybe an ACT insider could tell us more...
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[1207.3804] Examining the evidence for dynamical dark energy - 0 views

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    Hints of something interesting or data artefact? Also: http://arxiv.org/pdf/1207.4781v1.pdf
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Growth Histories in Bimetric Massive Gravity - 1 views

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    Massive Gravity is this year's must-have theory of modified gravity. The concept is simple - what if the graviton had a (very small) mass? However, building a consistent and viable theory from this idea has proved very difficult. It has now been achieved for the background-level cosmology, and can fit the accelerated expansion (with the usual fine-tuning problems, of course!) This paper takes the first steps towards the perturbation theory that needs to be developed if we are to test Massive Gravity with measurements of structure growth, etc.
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[1205.4033] On the local dark matter density - 3 views

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    An explanation of the anomalously low measurement of the local dark matter density that we discussed a few weeks ago?
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[1204.6044] Astrophysical Tests of Modified Gravity: Constraints from Distance Indicato... - 0 views

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    The chameleon mechanism suppresses the effects of a modified gravity theory in high-density environments. The authors of this paper suggest that this could lead to effects on stellar structure that would impact distance measures inferred from cepheid variables and red giant branch stars. Whilst it's not clear that the astrophysics involved is sufficiently well understood for such tests to be useful, I think there is some good thinking-outside-the-box here!
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[1204.1691] A tensor instability in the Eddington inspired Born-Infeld Theory of Gravity - 1 views

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    Celia visited us for several months last summer - this paper is the outcome of her work here. In EBI gravity there is an 'Eddington-dominated' epoch in the universe prior to radiation domination, which can avoid the need for a big bang singularity. However, it turns out that tensor perturbations in this early phase are unstable. It's particularly interesting that the instability only shows up at the perturbative level, whilst the background cosmology remains non-singular.
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Lensing of 21cm Fluctuations by Primordial Gravitational Waves - 4 views

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    The current upper limit on the tensor-to-scalar ratio r is ~0.2, and should improve by an order of magnitude with future experiments. These authors claim that measuring the curl component of the lensing power spectrum of 21cm emission could yield incredible constraints r~10^(-9) (though this headline figure corresponds to their most optimistic case). The angular resolution of our planned 21cm telescopes is the crucial quantity in determining these constraints.
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Seeing in the dark - II. Cosmic shear in the Sloan Digital Sky Survey - 0 views

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    Recommended by Jo.
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Halo Scale Predictions of Symmetron Modified Gravity - 1 views

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    There are a number of `screening' mechanisms that are designed to suppress the effects of modified gravity below cluster scales. What are the characteristic radii at which this switch-off occurs in the different mechanisms?
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Ultra-light Axions: Degeneracies with Massive Neutrinos and Forecasts for Future Cosmol... - 1 views

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    Axions are ultra-light particles that arise in string theory, and could make up some part of the dark matter in the universe. If so, what are the prospects for detecting their effects with galaxy surveys/CMB/weak lensing with future experiments? Come and ask the authors.
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[1108.5161] Hubble without the Hubble: cosmology using advanced gravitational-wave de... - 2 views

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    A new method to determine the luminosity-distance/redshift relation from gravitational waves, without the need to find an EM counterpart? I would love someone with more NS knowledge to explain the details!
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