Nonlinear thermoelectric response of quantum dots: renormalized dual fermions out of equilibrium

The thermoelectric transport properties of nanostructured devices continue to attract attention from theorists and experimentalist alike as the spatial confinement allows for a controlled approach to transport properties of correlated matter. Most of the existing work, however, focuses on thermoelectric transport in the linear regime despite the fact that the nonlinear conductance of correlated quantum dots has been studied in some detail throughout the last decade. Here, we review our recent work on the effect of particle-hole asymmetry on the nonlinear transport properties in the vicinity of the strong coupling limit of Kondo-correlated quantum dots and extend the underlying method, a renormalized superperturbation theory on the Keldysh contour, to the thermal conductance in the nonlinear regime. We determine the charge, energy, and heat current through the nanostructure and study the nonlinear transport coefficients, the entropy production, and the fate of the Wiedemann-Franz law in the non-thermal steady-state. Our approach is based on a renormalized perturbation theory in terms of dual fermions around the particle-hole symmetric strong-coupling limit.Comment: chapter contributed to 'New Materials for Thermoelectric Applications: Theory and Experiment' Springer Series: NATO Science for Peace and Security Series - B: Physics and Biophysics, Veljko Zlatic (Editor), Alex Hewson (Editor). ISBN: 978-9400749863 (2012

Dynamical Mean-Field Theory

The dynamical mean-field theory (DMFT) is a widely applicable approximation scheme for the investigation of correlated quantum many-particle systems on a lattice, e.g., electrons in solids and cold atoms in optical lattices. In particular, the combination of the DMFT with conventional methods for the calculation of electronic band structures has led to a powerful numerical approach which allows one to explore the properties of correlated materials. In this introductory article we discuss the foundations of the DMFT, derive the underlying self-consistency equations, and present several applications which have provided important insights into the properties of correlated matter.Comment: Chapter in "Theoretical Methods for Strongly Correlated Systems", edited by A. Avella and F. Mancini, Springer (2011), 31 pages, 5 figure

Immunophenotyping of Circulating T Helper Cells Argues for Multiple Functions and Plasticity of T Cells In Vivo in Humans - Possible Role in Asthma

BACKGROUND: The immune process driving eosinophilic and non-eosinophilic asthma is likely driven by different subsets of T helper (Th) cells. Recently, in vitro studies and animal studies suggest that Th cell subsets displays plasticity by changing their transcription factor or by expressing multiple transcription factors. Our aim was to determine whether individuals with asthma and elevated circulating eosinophils express signs of different regulatory immune mechanisms compared with asthmatics with low blood eosinophils and non-asthmatic control subjects. In addition, determine the relationship between eosinophilia and circulating Th cell subsets. METHODOLOGY/PRINCIPAL FINDINGS: Participants were selected from a random epidemiological cohort, the West Sweden Asthma Study. Immunophenotypes of fresh peripheral blood cells obtained from stable asthmatics, with and without elevated eosinophilic inflammation (EOS high and EOS low respectively) and control subjects, were determined by flow cytometry. No differences in the number of Th1 (T-bet), Th2 (GATA-3), Th17 (RORγt) or Treg (FOXP3) cells were observed between the groups when analysing each subset separately. However, in all groups, each of the Th subsets showed expression of additional canonical transcription factors T-bet, GATA-3, RORγt and FOXP3. Furthermore, by in vitro stimulation with anti-CD3/anti-CD28 there was a significant increase of single expressing GATA-3(+) and co-expressing T-bet(+)GATA-3(+) cells in the EOS high asthmatics in comparison with control subjects. In addition, T-bet(-)GATA-3(+)RORγt(+)FOXP3(+) were decreased in comparison to the EOS low asthmatics. Finally, in a group of control subjects we found that the majority of proliferating Th cells (CD4(+)CD25(+)Ki67(+)) expressed three or four transcription factors. CONCLUSIONS: The ability of human Th cells to express several regulatory transcription factors suggests that these cells may display plasticity in vivo

In Situ Patrolling of Regulatory T Cells Is Essential for Protecting Autoimmune Exocrinopathy

BACKGROUND: Migration of T cells, including regulatory T (Treg) cells, into the secondary lymph organs is critically controlled by chemokines and adhesion molecules. However, the mechanisms by which Treg cells regulate organ-specific autoimmunity via these molecules remain unclear. Although we previously reported autoimmune exocrinopathy resembling Sjögren's syndrome (SS) in the lacrimal and salivary glands from C-C chemokine receptor 7 (CCR7)-deficient mice, it is still unclear whether CCR7 signaling might specifically affect the dynamics and functions of Treg cells in vivo. We therefore investigated the cellular mechanism for suppressive function of Treg cells via CCR7 in autoimmunity using mouse models and human samples. METHODS AND FINDINGS: Patrolling Treg cells were detected in the exocrine organs such as lacrimal and salivary glands from normal mice that tend to be targets for autoimmunity while the Treg cells were almost undetectable in the exocrine glands of CCR7(-/-) mice. In addition, we found the significantly increased retention of CD4(+)CD25(+)Foxp3(+) Treg cells in the lymph nodes of CCR7(-/-) mice with aging. Although Treg cell egress requires sphingosine 1-phosphate (S1P), chemotactic function to S1P of CCR7-/- Treg cells was impaired compared with that of WT Treg cells. Moreover, the in vivo suppression activity was remarkably diminished in CCR7(-/-) Treg cells in the model where Treg cells were co-transferred with CCR7(-/-) CD25(-)CD4(+) T cells into Rag2(-/-) mice. Finally, confocal analysis showed that CCR7(+)Treg cells were detectable in normal salivary glands while the number of CCR7(+)Treg cells was extremely decreased in the tissues from patients with Sjögren's syndrome. CONCLUSIONS: These results indicate that CCR7 essentially governs the patrolling functions of Treg cells by controlling the traffic to the exocrine organs for protecting autoimmunity. Characterization of this cellular mechanism could have clinical implications by supporting development of new diagnosis or treatments for the organ-specific autoimmune diseases such as Sjögren's syndrome and clarifying how the local immune system regulates autoimmunity

Update on the Combined Analysis of Muon Measurements from Nine Air Shower Experiments

Over the last two decades, various experiments have measured muon densities in extensive air showers over several orders of magnitude in primary energy. While some experiments observed differences in the muon densities between simulated and experimentally measured air showers, others reported no discrepancies. We will present an update of the meta-analysis of muon measurements from nine air shower experiments, covering shower energies between a few PeV and tens of EeV and muon threshold energies from a few 100 MeV to about 10GeV. In order to compare measurements from different experiments, their energy scale was cross-calibrated and the experimental data has been compared using a universal reference scale based on air shower simulations. Above 10 PeV, we find a muon excess with respect to simulations for all hadronic interaction models, which is increasing with shower energy. For EPOS-LHC and QGSJet-II.04 the significance of the slope of the increase is analyzed in detail under different assumptions of the individual experimental uncertainties

A SPDE Maximum Principle for Stochastic Differential Games under Partial Information with Application to Optimal Portfolios on Fixed Income Markets

In this paper we aim at establishing a necessary and sufficient maximum principle for partial information control of general stochastic games, where the controlled process is given by a stochastic reaction-diffusion equation with jumps. As an application of this result we study a zero-sum stochastic differential game on a fixed income market, that is we solve the problem of finding an optimal strategy for portfolios of constant maturity interest rate derivatives managed by a trader who plays against various "market scenarios". Here we permit the restriction that the trader has limited access to market information

Risk Indifference Pricing of Functional Claims of the Yield Surface in the Presence of Partial Information

In this paper we study the problem of risk indifference pricing of interest rate claims which are functionals of a bond yield surface under partial information. Our approach to solve this problem relies on a maximum principle for partial information control of stochastic differential games based on generalized bond portfolios. The latter method enables us to establish an explicit representation of the risk indifference price of such claims