4,714 research outputs found
Jet substructure and probes of CP violation in Vh production
We analyse the hVV (V = W, Z) vertex in a model independent way using Vh
production. To that end, we consider possible corrections to the Standard Model
Higgs Lagrangian, in the form of higher dimensional operators which parametrise
the effects of new physics. In our analysis, we pay special attention to linear
observables that can be used to probe CP violation in the same. By considering
the associated production of a Higgs boson with a vector boson (W or Z), we use
jet substructure methods to define angular observables which are sensitive to
new physics effects, including an asymmetry which is linearly sensitive to the
presence of CP odd effects. We demonstrate how to use these observables to
place bounds on the presence of higher dimensional operators, and quantify
these statements using a log likelihood analysis. Our approach allows one to
probe separately the hZZ and hWW vertices, involving arbitrary combinations of
BSM operators, at the Large Hadron Collider.Comment: 37 pages, 17 figures; v3 matches published versio
The Discrete Fundamental Group of the Associahedron, and the Exchange Module
The associahedron is an object that has been well studied and has numerous
applications, particularly in the theory of operads, the study of non-crossing
partitions, lattice theory and more recently in the study of cluster algebras.
We approach the associahedron from the point of view of discrete homotopy
theory. We study the abelianization of the discrete fundamental group, and show
that it is free abelian of rank . We also find a combinatorial
description for a basis of this rank. We also introduce the exchange module of
the type cluster algebra, used to model the relations in the cluster
algebra. We use the discrete fundamental group to the study of exchange module,
and show that it is also free abelian of rank .Comment: 16 pages, 4 figure
Synopsis of early field test results from the gravity gradiometer survey system
Although the amount of data yielded by the initial airborne and surface tests was modest, it was sufficient to demonstrate that the full gravity gradient tensor was successfully measured from moving platforms both in the air and on the surface. The measurements were effectively continuous with spatial along-track resolution limited only by choice of integration lengths taken to reduce noise. The airborne data were less noisy (800 E squared/Hz typical) than were the Gravity Gradiometer Survey System (GGSS) measurements taken at the surface (5000 E squared/Hz typical). Single tracks of surface gravity disturbances recovered from airborne data were accurate to 3 to 4 mgal in each component of gravity when compared to 5 x 5 mean gravity anomalies over a 90 km track. Multitrack processing yielded 2 to 3 mgal when compared to 5 x 5 mean anomalies. Deflection of the vertical recovery over a distance of 150 km was about one arcsecond
Windows into Non-Euclidean Spaces
Two microlens arrays that are separated by the sum of their focal lengths form arrays of micro-telescopes. Parallel light rays that pass through corresponding lenses remain parallel, but the direction of the transmitted light rays is different. This remains true if corresponding lenses do not share an optical axis (i.e. if the two microlens arrays are shifted with respect to each other). The arrays described above are examples of generalized confocal lenslet arrays, and the light-ray-direction change in these devices is well understood [Oxburgh et al., Opt. Commun. 313, 119 (2014)]. Here we show that such micro-telescope arrays change light-ray direction like the interface between spaces with different metrics. To physicists, the concept of metrics is perhaps most familiar from General Relativity (where it is applied to spacetime, not only space, like it is here) and Transformation Optics [Pendry et al., Science 312, 1780 (2006)], where different materials are treated like spaces with different optical metrics. We illustrate the similarities between micro-telescope arrays and metric interfaces with raytracing simulations. Our results suggest the possibility of realising transformation-optics devices with micro-telescope arrays, which we investigate elsewhere
Progress towards omnidirectional transformation optics with lenses
We study, theoretically, omni-directional Euclidean transformation-optics (TO) devices comprising planar, light-ray-direction changing, imaging, interfaces. We initially studied such devices in the case when the interfaces are homogeneous, showing that very general transformations between physical and electromagnetic space are possible. We are now studying the case of inhomogeneous interfaces. This case is more complex to analyse, but the inhomogeneous interfaces include ideal thin lenses, which gives rise to the hope that it might be possible to construct practical omni-directional TO devices from lenses alone. Here we report on our progress in this direction
The effects of river flooding on dioxin and PCBs in beef
In 2008-2010, samples of meat from 40 beef cattle, along with grass, soil and commercial feed, taken from ten matched pairs of flood-prone and control farms, were analysed for PCDD/Fs and PCBs. Concentrations were higher in soil and grass from flood-prone farms. The beef samples from flood-prone farms had total TEQ levels about 20% higher than on control farms. A majority of flood-prone farms (7/10) had higher median levels in beef than on the corresponding control farm. This first controlled investigation into PCDD/F and PCB contamination in beef produced on flood-prone land, presents robust evidence that flooding is a contaminant transfer mechanism to cattle raised on river catchments with a history of urbanisation and industrialisation. PCDD/F and PCB sources in these river systems are likely to be a result of the legacy of contamination from previous industrialisation, as well as more recent combustion activity or pollution events. Crow
A Perception of Change, A Change of Perception
Change is a constant reminder that permanence is the ultimate illusion. It is through the creation of hyper-realistic, ceramic sculpture that I explore the relationship between nature, humans, and the phenomenon of impermanence. I seek to expose the beauty that often results from decay while, at the same time, making my viewer question their own perception of the world around them. The juxtaposition of natural and man-made features in combination with the skewing of scale, proportion, and material, creates an altered perspective – forcing the viewer to look closer. By combining both human and natural elements within my work I highlight the fact that we are not separate from nature but are, in fact, part of it
Dark-Matter Decays and Self-Gravitating Halos
We consider models in which a dark-matter particle decays to a slightly less
massive daughter particle and a noninteracting massless particle. The decay
gives the daughter particle a small velocity kick. Self-gravitating dark-matter
halos that have a virial velocity smaller than this velocity kick may be
disrupted by these particle decays, while those with larger virial velocities
will be heated. We use numerical simulations to follow the detailed evolution
of the total mass and density profile of self-gravitating systems composed of
particles that undergo such velocity kicks as a function of the kick speed
(relative to the virial velocity) and the decay time (relative to the dynamical
time). We show how these decays will affect the halo mass-concentration
relation and mass function. Using measurements of the halo mass-concentration
relation and galaxy-cluster mass function to constrain the
lifetime--kick-velocity parameter space for decaying dark matter, we find
roughly that the observations rule out the combination of kick velocities
greater than 100 km/s and decay times less than a few times the age of the
Universe.Comment: 17 pages, 10 figures, replaced with published versio
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