Loschmidt echoes in two-body random matrix ensembles

Fidelity decay is studied for quantum many-body systems with a dominant independent particle Hamiltonian resulting e.g. from a mean field theory with a weak two-body interaction. The diagonal terms of the interaction are included in the unperturbed Hamiltonian, while the off-diagonal terms constitute the perturbation that distorts the echo. We give the linear response solution for this problem in a random matrix framework. While the ensemble average shows no surprising behavior, we find that the typical ensemble member as represented by the median displays a very slow fidelity decay known as ``freeze''. Numerical calculations confirm this result and show, that the ground state even on average displays the freeze. This may contribute to explanation of the ``unreasonable'' success of mean field theories.Comment: 9 pages, 5 figures (6 eps files), RevTex; v2: slight modifications following referees' suggestion

1/f noise in the Two-Body Random Ensemble

We show that the spectral fluctuations of the Two-Body Random Ensemble (TBRE) exhibit 1/f noise. This result supports a recent conjecture stating that chaotic quantum systems are characterized by 1/f noise in their energy level fluctuations. After suitable individual averaging, we also study the distribution of the exponent \alpha in the 1/f^{\alpha} noise for the individual members of the ensemble. Almost all the exponents lie inside a narrow interval around \alpha=1 suggesting that also individual members exhibit 1/f noise, provided they are individually unfoldedComment: 4 pages, 3 figures, Accepted for publication in Phys. Rev.

The potentiation effects of high intensity warm ups in a middle distance context

n previous research (Long & French, 2013a, 2013b, 2013c, 2014a) we have explored how since the start of athletic competition, coaches have attempted to create innovative methods of preparing athletes to perform at their optimum. Much of the established coach education literature has focused on the effects of long term preparation and planning, now known as Periodization, in terms of how different activities are performed in the weeks and months leading up to a competition (Bompa and Haff, 2009). This current research focuses on activities undertaken by athletes under the supervision of coaches immediately prior to performance and in this case we are specifically looking at how mode of warm can produce a potentiation effect. Evidence has suggested that warm ups can both reduce injury (Thacker et al., 2004) and increase both endurance and ‘power’ performance (Young & Behm, 2003). This being said, we have argued (Long & French, 2013a, 2013b, 2013c) that whilst many of the practices seem not to be new and have been implemented by coaches over a period of time, the effectiveness and scientific underpinnings are only now being understood. More specifically, we have begun to make the argument that it is not only the duration of the warm up which 2 matters but rather the intensity of the warm up undertaken before training and competition

Clinical, histological and prognostic features of a novel nail-bed lesion of cats: 41 cases

There is a distinct subset of lesions arising on the digits of cats, located at or close to the nail-bed epithelium, which are typically composed of proliferative fibroblast-like cells, multinucleate giant cells and areas of osseous metaplasia, but currently there is no published literature detailing the clinical or histological features of these lesions. This study identified 41 such cases from two large commercial diagnostic laboratories and assessed various histological and clinical features; 22 cases had additional follow-up data available

FOOD AND HYGIENE OF OLD AGE.: Read by Title in the Section of Physiology and Dietetics, at the Forty third Annual Meeting of the American Medical Association, held at Detroit, Mich., June 7, 1892.

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Mobile Phone Faraday Cage

A Faraday cage is an interesting physics phenomena where an electromagnetic wave can be excluded from a volume of space by enclosure with an electrically conducting material. The practical application of this in the classroom is to block the signal to a mobile phone by enclosing it in a metal can! The background of the physics behind this is described in some detail followed by a explanation of some demonstrations and experiments which I have used

Violation of the isotropic-ℓ\ell approximation in overdoped La_{2-x}Sr_xCuO_4

Magnetotransport measurements on the overdoped cuprate La_{1.7}Sr_{0.3}CuO_4 are fitted using the Ong construction and band parameters inferred from angle-resolved photoemission. Within a band picture, the low temperature Hall data can only be fitted satisfactorily by invoking strong basal-plane anisotropy in the mean-free-path $\ell$. This violation of the isotropic-$\ell$ approximation supports a picture of dominant small-angle elastic scattering in cuprates due to out-of-plane substitutional disorder. We show that both band anisotropy and anisotropy in the elastic scattering channel strongly renormalize the Hall coefficient in overdoped La_{2-x}Sr_xCuO_4 over a wide doping and temperature range.Comment: 4 pages, 4 figure