Unconventional superconductivity in iron-base superconductors in a three-band model

Iron-base superconductors exhibits features of systems where the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase, a superconducting state with non-zero total momentum of Cooper pairs, is actively sought. Experimental and theoretical evidence points strongly to the FFLO phase in these materials above the Pauli limit. In this article we discuss the ground state of iron-base superconductors near the critical magnetic field and the full $h-T$ phase diagram for pnictides in case of intra-band pairing, in a three-band model with $s_{\pm}$ symmetry.Comment: RevTeX, 5 pages, 3 figures. Presented on "XVI National Conference of Superconductivity", October 7-12, 2013, Zakopane, Polan

Nationalizations and effciency

We develop a theoretical model in which ?rms are either private or state-owned. When ?rms become insolvent, the government can intervene with general measures, like subsidies, or by nationalizing ?rms. The government only intervenes when the bankruptcy of a ?rm entails social costs. In a stylized model, we analyze how government interventions a?ect allocative and productive efficiency. Nationalization of private ?rms in case unpro?table investments were made, leads to increased allocative efficiency despite private ownership. The effort level chosen by the managers working for ?rms is also affected by government intervention with an impact on productive efficiency

The Mu-MASS (MuoniuM lAser SpectroScopy) experiment

We present a new experiment, Mu-MASS, aiming for a 1000-fold improvement in the determination of the 1S-2S transition frequency of Muonium (M), the positive-muon/electron bound state. This substantial improvement beyond the current state-of-the-art relies on the novel cryogenic M converters and confinement techniques we developed, on the new excitation and detection schemes which we implemented for positronium spectroscopy and the tremendous advances in generation of UV radiation. This experiment is planned to be performed at the Paul Scherrer Institute (PSI). Interesting anomalies in the muon sector have accumulated: notably the famous anomalous muon magnetic moment (g-2) and the muonic hydrogen Lamb shift measurement which prompted the so-called proton charge radius puzzle. These tantalizing results triggered vibrant activity on both experimental and theoretical sides. Different explanations have been put forward including exciting solutions invoking New Physics beyond the Standard Model. Mu-MASS could contribute to clarifying the origin of these anomalies by providing robust and reliable values of fundamental constants such as the muon mass and a value of the Rydberg constant independent of finite size effects.Comment: 11 pages, 3 figures, prepared for the proceedings of the LEAP 2018 conferenc

Nationalizations and effciency

We develop a theoretical model in which ?rms are either private or state-owned. When ?rms become insolvent, the government can intervene with general measures, like subsidies, or by nationalizing ?rms. The government only intervenes when the bankruptcy of a ?rm entails social costs. In a stylized model, we analyze how government interventions a?ect allocative and productive efficiency. Nationalization of private ?rms in case unpro?table investments were made, leads to increased allocative efficiency despite private ownership. The effort level chosen by the managers working for ?rms is also affected by government intervention with an impact on productive efficiency.nationalization; efficiency

Size and Soft Budget Constraints

There is much evidence against the so-called "too big to fail" hypothesis in the case of bailouts to sub-national governments. We look at a model where districts of different size provide local public goods with positive spillovers. Matching grants of a central government can induce socially-efficient provision, but districts can still exploit the intervening central government by inducing direct financing. We show that the ability of a district to induce a bailout from the central government and district size are negatively correlated.bailouts, soft-budget constraints, jurisdictional size, public goods, spillovers

Energy current and energy fluctuations in driven quantum wires

We discuss the energy current and the energy fluctuations in an isolated quantum wire driven far from equilibrium. The system consists of interacting spinless fermions and is driven by a time--dependent magnetic flux. The energy current is defined by the continuity equation for the energy density which is derived both for homogeneous as well as for inhomogeneous systems. Since the total energy is not conserved in the driven system, the continuity equation includes the source terms which are shown to represent the Joule heating effects. For short times and weak drivings the energy current agrees with the linear response theory. For stronger fields or longer times of driving the system enters the quasiequilibrium regime when the energy current gradually diminishes due to the heating effects. Finally, for even stronger driving the energy current is shown to undergo a damped Bloch oscillations. The energy spread also increases upon driving. However, the time--dependence of this quantity in the low field regime is quite unexpected since it is determined mostly by the time of driving being quite independent of the instantaneous energy of the system.Comment: 9 pages, 2 figures, Proc. NATO Adv. Research Workshop Nanotechnology in the security systems, Ed. S. Kruchinin, Yalta, Ukraine, 201

Size and soft budget constraints

There is much evidence against the so-called "too big to fail" hypothesis in the case of bailouts to sub-national governments. We look at a model where districts of different size provide local public goods with positive spillovers. Matching grants of a central government can induce socially-efficient provision, but districts can still exploit the intervening central government by inducing direct financing. We show that the ability of a district to induce a bailout from the central government and district size are negatively correlated

Can we observe the gravitational quantum states of Positronium?

In this paper we consider the feasibility of observing the gravitational quantum states of positronium. The proposed scheme employs the flow-throw technique used for the first observation of this effect with neutrons. Collimation and Stark deceleration of Rydberg positronium atoms allow to select the required velocity class. If this experiment could be realized with positronium it would lead to a determination of g for this matter-antimatter system at the few % level. As discussed in this contribution, most of the required techniques are currently available but important milestones have to be demonstrated experimentally before such an experiment could become reality. Those are: the efficient focusing of a bunched positron beam, Stark deceleration of Rydberg positronium and its subsequent excitation into states with large angular momentum. We provide an estimate of the efficiencies we expect for these steps and assuming those could be confirmed we calculate the signal rate.Comment: 12 pages, 1 figure, contribution to the GRANIT 2014 workshop: Quantum gravitationnal spectroscopy with ultra-cold system

Optical trapping of anti-hydrogen towards an atomic anti-clock

The Anti-Matter Factory at CERN is gearing up, commissioning of the Extra Low ENergy Antiprotons (ELENA) ring is ongoing and the first anti-protons are foreseen to circulate in the decelerator very soon. The unprecedented flux of low energy antiprotons delivered by ELENA will open a new era for precision tests with antimatter including laser and microwave spectroscopy and tests of its gravitational behaviour. Here we propose a scheme to load the ultra cold anti-hydrogen atoms that will be produced by the GBAR experiment in an optical lattice tuned at the magic wavelength of the 1S-2S transition in order to measure this interval at a level comparable or even better than its matter counter part. This will provide the most sensitive test of CPT symmetry parametrised in the framework of the Standard Model Extension.Comment: 7 pages, 2 Figure