The Highest Energy Neutrinos

Measurements of the arrival directions of cosmic rays have not revealed their sources. High energy neutrino telescopes attempt to resolve the problem by detecting neutrinos whose directions are not scrambled by magnetic fields. The key issue is whether the neutrino flux produced in cosmic ray accelerators is detectable. It is believed that the answer is affirmative, both for the galactic and extragalactic sources, provided the detector has kilometer-scale dimensions. We revisit the case for kilometer-scale neutrino detectors in a model-independent way by focussing on the energetics of the sources. The real breakthrough though has not been on the theory but on the technology front: the considerable technical hurdles to build such detectors have been overcome. Where extragalactic cosmic rays are concerned an alternative method to probe the accelerators consists in studying the arrival directions of neutrinos produced in interactions with the microwave background near the source, i.e. within a GZK radius. Their flux is calculable within large ambiguities but, in any case, low. It is therefore likely that detectors that are larger yet by several orders of magnitudes are required. These exploit novel techniques, such as detecting the secondary radiation at radio wavelengths emitted by neutrino induced showers.Comment: 16 pages, pdflatex, 7 jpg figures, ICRC style files included. Highlight talk presented at the 30th International Cosmic Ray Conference, Merida, Mexico, 200

Effective Field Theories and Inflation

We investigate the possible influence of very-high-energy physics on inflationary predictions focussing on whether effective field theories can allow effects which are parametrically larger than order H^2/M^2, where M is the scale of heavy physics and H is the Hubble scale at horizon exit. By investigating supersymmetric hybrid inflation models, we show that decoupling does not preclude heavy-physics having effects for the CMB with observable size even if H^2/M^2 << O(1%), although their presence can only be inferred from observations given some a priori assumptions about the inflationary mechanism. Our analysis differs from the results of hep-th/0210233, in which other kinds of heavy-physics effects were found which could alter inflationary predictions for CMB fluctuations, inasmuch as the heavy-physics can be integrated out here to produce an effective field theory description of low-energy physics. We argue, as in hep-th/0210233, that the potential presence of heavy-physics effects in the CMB does not alter the predictions of inflation for generic models, but does make the search for deviations from standard predictions worthwhile.Comment: 19 pages, LaTeX, no figures, uses JHEP

Post-truth and anthropogenic climate change: asking the right questions

The connection between climate skepticism and climate denial and what has become known as post‐truth culture has become the subject of much interest in recent years. This has lead to intense debates among scientists and activists about how to respond to this changed cultural context and the ways in which it is held to obstruct wider acceptance of climate science. Drawing on research in the sociology of scientific knowledge, science and technology studies, social psychology, and philosophical reflections on evidential reasoning, it is argued that these debates are focused on the wrong topic. The idea of post‐truth implies that a once‐straightforward linear relationship between scientific evidence and decision‐making has been eroded. But such an idealized relationship never existed. The proper role of scientific evidence in informing belief and action in response to the prospect of anthropogenic climate change needs reconsideration. A key part of this is to make uncertainties related to processes within the climate system and their potential outcomes into the main focus of public discussion around climate change. Instead of keeping the focus of debate on how to “get the science right,” such a reframing makes precautionary questions about the prospect of unacceptable losses into the main focus. This brings a variety of ethical and political values into the debate, perhaps creating better conditions for a minimal consensus about what to do