Primordial magnetic fields at preheating

Using lattice techniques we investigate the generation of long range cosmological magnetic fields during a cold electroweak transition. We will show how magnetic fields arise, during bubble collisions, in the form of magnetic strings. We conjecture that these magnetic strings originate from the alignment of magnetic dipoles associated with EW sphaleron-like configurations. We also discuss the early thermalisation of photons and the turbulent behaviour of the scalar fields after tachyonic preheating.Comment: 7 pages. Talk presented at Lattice200

Shot Noise in Mesoscopic Diffusive Andreev Wires

We study shot noise in mesoscopic diffusive wires between a normal and a superconducting terminal. We particularly focus on the regime, in which the proximity-induced reentrance effect is important. We will examine the difference between a simple Boltzmann-Langevin description, which neglects induced correlations beyond the simple conductivity correction, and a full quantum calculation. In the latter approach, it turns out that two Andreev pairs propagating coherently into the normal metal are anti-correlated for E<E_c, where E_c=D/L^2 is the Thouless energy. In a fork geometry the flux-sensitive suppression of the effective charge was confirmed experimentally.Comment: 12 pages, proceedings of the NATO ARW MQO, Bled, Sloveni

Full Counting Statistics of Superconductor--Normal-Metal Heterostructures

The article develops a powerful theoretical tool to obtain the full counting statistics. By a slight extension of the standard Keldysh method we can access immediately all correlation functions of the current operator. Embedded in a quantum generalization of the circuit theory of electronic transport, we are able to study the full counting statistics of a large class of two-terminal contacts and multi-terminal structures, containing superconductors and normal metals as elements. The practical use of the method is demonstrated in many examples.Comment: 35 pages, contribution to "Quantum Noise", ed. by Yu.V. Nazarov and Ya.M. Blanter, minor changes in text, references adde

Shot noise in mesoscopic systems

This is a review of shot noise, the time-dependent fluctuations in the electrical current due to the discreteness of the electron charge, in small conductors. The shot-noise power can be smaller than that of a Poisson process as a result of correlations in the electron transmission imposed by the Pauli principle. This suppression takes on simple universal values in a symmetric double-barrier junction (suppression factor 1/2), a disordered metal (factor 1/3), and a chaotic cavity (factor 1/4). Loss of phase coherence has no effect on this shot-noise suppression, while thermalization of the electrons due to electron-electron scattering increases the shot noise slightly. Sub-Poissonian shot noise has been observed experimentally. So far unobserved phenomena involve the interplay of shot noise with the Aharonov-Bohm effect, Andreev reflection, and the fractional quantum Hall effect.Comment: 37 pages, Latex, 10 figures (eps). To be published in "Mesoscopic Electron Transport," edited by L. P. Kouwenhoven, G. Schoen, and L. L. Sohn, NATO ASI Series E (Kluwer Academic Publishing, Dordrecht

Analisis terhadap tahap-tahap ketagihan menurut teori al-‘Ishq Ibnu Qayyim Al-Jawziyyah

Ketagihan merupakan satu penyakit minda yang mempunyai tahap-tahap ketegarannya yang tersendiri. Ini merujuk kepada realiti kerinduan seseorang terhadap sesuatu itu berbeza-beza dan mempunyai simptom yang berlainan. Para sarjana Islam turut membuat penelitian terhadap aspek kerinduan kepada sesuatu dalam karya-karya mereka. Antaranya tokoh ilmuan Islam yang terkenal, Ibnu Qayyim al-Jawziyyah yang memperincikan hal ini dalam konsep atau teori al-‘Ishq di dalam beberapa kitabnya. Kajian ini akan menganalisis tahap-tahap ketagihan berdasarkan teori al-‘Ishq oleh Ibnu Qayyim. Kajian ini menggunakan metod induktif, deduktif, serta komparatif. Hasil kajian mendapati terdapat hubungan yang sangat rapat di antara teori al-‘Ishq dan ketagihan dari sudut definisi dan peringkat-peringkatnya. Justeru, pendekatan terapi al-‘Ishq yang dicadangkan oleh Ibn Qayyim berdasarkan tahap-tahap keasyikan boleh diterokai sebagai suatu input dalam mengemukakan langkah-langkah pemulihan terhadap sebarang isu yang melibatkan ketagihan