Photons as quasi-charged particles

The Schrodinger motion of a charged quantum particle in an electromagnetic potential can be simulated by the paraxial dynamics of photons propagating through a spatially inhomogeneous medium. The inhomogeneity induces geometric effects that generate an artificial vector potential to which signal photons are coupled. This phenomenon can be implemented with slow light propagating through an a gas of double-Lambda atoms in an electromagnetically-induced transparency setting with spatially varied control fields. It can lead to a reduced dispersion of signal photons and a topological phase shift of Aharonov-Bohm type

A new proof that alternating links are non-trivial

We use a simple geometric argument and small cancellation properties of link groups to prove that alternating links are non-trivial. This proof uses only classic results in topology and combinatorial group theory.Comment: Minor changes. To appear in Fundamenta Mathematica

Formalizing Size-Optimal Sorting Networks: Extracting a Certified Proof Checker

Since the proof of the four color theorem in 1976, computer-generated proofs have become a reality in mathematics and computer science. During the last decade, we have seen formal proofs using verified proof assistants being used to verify the validity of such proofs. In this paper, we describe a formalized theory of size-optimal sorting networks. From this formalization we extract a certified checker that successfully verifies computer-generated proofs of optimality on up to 8 inputs. The checker relies on an untrusted oracle to shortcut the search for witnesses on more than 1.6 million NP-complete subproblems.Comment: IMADA-preprint-c

Coloring random graphs

We study the graph coloring problem over random graphs of finite average connectivity $c$. Given a number $q$ of available colors, we find that graphs with low connectivity admit almost always a proper coloring whereas graphs with high connectivity are uncolorable. Depending on $q$, we find the precise value of the critical average connectivity $c_q$. Moreover, we show that below $c_q$ there exist a clustering phase $c\in [c_d,c_q]$ in which ground states spontaneously divide into an exponential number of clusters and where the proliferation of metastable states is responsible for the onset of complexity in local search algorithms.Comment: 4 pages, 1 figure, version to app. in PR

Raman Adiabatic Transfer of Optical States

We analyze electromagnetically induced transparency and light storage in an ensemble of atoms with multiple excited levels (multi-Lambda configuration) which are coupled to one of the ground states by quantized signal fields and to the other one via classical control fields. We present a basis transformation of atomic and optical states which reduces the analysis of the system to that of EIT in a regular 3-level configuration. We demonstrate the existence of dark state polaritons and propose a protocol to transfer quantum information from one optical mode to another by an adiabatic control of the control fields

Quality of life of elderly persons with newly diagnosed cancer.

The aim was to investigate quality of life (QoL) in elderly persons newly diagnosed with cancer (65+ years) in relation to age, contact with the health-care system, ability to perform activities of daily living (ADL), hope, social network and support, and to identify which factors were associated with low QoL. The sample consisted of 101 patients (75 women and 26 men) newly diagnosed with cancer. EORTC QLQ-C30, Nowotny's Hope Scale, Katz ADL and the Interview Schedule for Social Interaction (ISSI) were used. The analysis was carried out in four age groups and revealed no significant differences in QoL. Compared with the other age groups, those of a high age (80+ years) more often lived alone, used more home-help service and had a smaller social network. Factors associated with low QoL were 'no other incomes than retirement pension', 'low level of hope' and 'lung cancer'. In addition, 'being told that the cancer disease has not come to an end', 'needing more help in activities of daily living', 'getting help from grown-up children' and 'needing help with PADL' were associated with low QoL. Those at risk of inferior QoL, that is, having poor economy, low level of hope and lung cancer need special attendance and specific interventions to improve QoL

The Joint Vienna Institute

"How does the intellectual role played by international training organisations fit into the contemporary architecture of global governance? The international diffusion of economic policy ideas represents one of the core dimensions of contemporary global governance, which has generated heated controversy in recent years with international institutions such as the International Monetary Fund (IMF) and the World Bank castigated for championing a ‘one-size-fits-all’ brand of neoliberal economic reform. Yet while substantial scholarly attention has focused on analysing the effects of the formal compliance mechanisms that the IMF and the World Bank rely on to implement neoliberal policy changes in borrowing countries, such as loan conditionality, less attention has been devoted to exploring the intermediate avenues through which neoliberal ideas travel from global governance institutions to national governance contexts. This article aims to address this gap in the study of contemporary global governance and neoliberal policy diffusion through critically examining the evolving role of the Joint Vienna Institute (JVI), an international training organisation set up after the end of the Cold War to transmit global ‘best practice’ economic policy ideas to national officials in post-communist economies.

Polynomial iterative algorithms for coloring and analyzing random graphs

We study the graph coloring problem over random graphs of finite average connectivity $c$. Given a number $q$ of available colors, we find that graphs with low connectivity admit almost always a proper coloring whereas graphs with high connectivity are uncolorable. Depending on $q$, we find the precise value of the critical average connectivity $c_q$. Moreover, we show that below $c_q$ there exist a clustering phase $c\in [c_d,c_q]$ in which ground states spontaneously divide into an exponential number of clusters. Furthermore, we extended our considerations to the case of single instances showing consistent results. This lead us to propose a new algorithm able to color in polynomial time random graphs in the hard but colorable region, i.e when $c\in [c_d,c_q]$.Comment: 23 pages, 10 eps figure

Operation of a Bloch oscillator

We report the operation of a Bloch oscillator. The active medium was a staticvoltage driven, doped GaAs/AlAs superlattice which was electromagnetically coupled to a resonator. The oscillator produced tuneable microwave radiation (frequency ~ 60 GHz; power ~ 0.5 mW; efficiency ~ 4 %). The gain (~ 10^4 /cm) was due to the nonlinearity mediated by miniband electrons. We also present a theory of the oscillator. The Bloch oscillator should in principle be feasible for generation of radiation up to frequencies of 10 THz and more.Comment: 9 pages, 4 figure