Search results for "Names"

Tensor tomography in periodic slabs

2018

Abstract The X-ray transform on the periodic slab [ 0 , 1 ] × T n , n ≥ 0 , has a non-trivial kernel due to the symmetry of the manifold and presence of trapped geodesics. For tensor fields gauge freedom increases the kernel further, and the X-ray transform is not solenoidally injective unless n = 0 . We characterize the kernel of the geodesic X-ray transform for L 2 -regular m -tensors for any m ≥ 0 . The characterization extends to more general manifolds, twisted slabs, including the Mobius strip as the simplest example.

Effects of Biochar Addition on Rill Flow Resistance

2021

The development of rills on a hillslope whose soil is amended by biochar remains a topic to be developed. A theoretical rill flow resistance equation, obtained by the integration of a power velocity distribution, was assessed using available measurements at plot scale with a biochar added soil. The biochar was incorporated and mixed with the arable soil using a biochar content BC of 6 and 12 kg m−2. The developed analysis demonstrated that an accurate estimate of the velocity profile parameter Гv can be obtained by the proposed power equation using an exponent e of the Reynolds number which decreases for increasing BC values. This result pointed out that the increase of biochar content dump…

Stochastic dynamical modelling of spot freight rates

2014

Based on empirical analysis of the Capesize and Panamax indices, we propose different continuous-time stochastic processes to model their dynamics. The models go beyond the standard geometric Brownian motion, and incorporate observed effects like heavy-tailed returns, stochastic volatility and memory. In particular, we suggest stochastic dynamics based on exponential Levy processes with normal inverse Gaussian distributed logarithmic returns. The Barndorff-Nielsen and Shephard stochastic volatility model is shown to capture time-varying volatility in the data. Finally, continuous-time autoregressive processes provide a class of models sufficiently rich to incorporate short-term persistence …

Relativistic wave equations from supergroup quantization

1983

A formalism of geometric quantization recently introduced which is based on the consideration of Lie groups which are central extensions by U(1) is applied to the relativistic case by using the N-2 super Poincare group with a central charge.

Fractional Fourier Transforms and Geometrical Optics

2010

Hybrid WENO schemes for polydisperse sedimentation models

2015

International audience; Polydisperse sedimentation models can be described by a strongly coupled system of conservation laws for the concentration of each species of solids. Typical solutions for the sedimentation model considered for batch settling in a column include stationary kinematic shocks separating layers of sediment of different composition. This phenomenon, known as segregation of species, is a specially demanding task for numerical simulation due to the need of accurate numerical simulations. Very high-order accurate solutions can be constructed by incorporating characteristic information, available due to the hyperbolicity analysis made in Donat and Mulet [A secular equation fo…

Emmy Noether’s Long Struggle to Habilitate in Göttingen

2020

Doctoral degrees have a long prehistory, but the modern Ph.D. first arose as part of an educational reform launched at the German universities. Over the course of the nineteenth century, this degree came to be awarded not merely to those who displayed a command of established knowledge in an academic field.

Diving into Math with Emmy Noether

2020

Some 100 years ago a notice appeared in the journal of the German Mathematical Society that read: “Dr. Emmy Noether has habilitated as a lecturer in mathematics at Gottingen University.” This quiet announcement was actually the resounding final chord in a long struggle that went on for four years and only ended on June 4, 1919, when Noether joined the Gottingen faculty.

Max von laue’s role in the relativity revolution

2008

Whereas countless studies have been devoted to Einstein’s work on relativity, the contributions of several other major protagonists have received comparatively little attention. Within the immediate German context, no single figure played a more important role in developing the consequences of the special theory of relativity (SR) than Max von Laue (1879–1960). Although remembered today mainly for his discovery of x-ray diffraction in 1912 – an achievement for which he was awarded the Nobel Prize – Laue’s accomplishments in promoting the theory of relativity were of crucial importance. They began early, well before most physicists even knew anything about a mysterious Swiss theoretician nam…

Klein, Mittag-Leffler, and the Klein-Poincaré Correspondence of 1881–1882

2018

If a modern-day Plutarch were to set out to write the “Parallel lives” of some famous modern-day mathematicians, he could hardly do better than to begin with the German, Felix Klein (1849–1925), and the Swede, Gosta Mittag-Leffler (1846–1927). Both lived in an age ripe with possibilities for the mathematics profession and, like few of their contemporaries, they seized upon these new opportunities whenever and however they arose. Even when their chances for success looked dismal, they forged ahead, winning over the skeptics as they did so. Although accomplished and prolific researchers (Klein’s work has even enjoyed the appellation “great”), they owed much of their success to their talents a…