On the Key-Uncertainty of Quantum Ciphers and the Computational Security of One-way Quantum Transmission

We consider the scenario where Alice wants to send a secret (classical) $n$-bit message to Bob using a classical key, and where only one-way transmission from Alice to Bob is possible. In this case, quantum communication cannot help to obtain perfect secrecy with key length smaller then $n$. We study the question of whether there might still be fundamental differences between the case where quantum as opposed to classical communication is used. In this direction, we show that there exist ciphers with perfect security producing quantum ciphertext where, even if an adversary knows the plaintext and applies an optimal measurement on the ciphertext, his Shannon uncertainty about the key used is almost maximal. This is in contrast to the classical case where the adversary always learns $n$ bits of information on the key in a known plaintext attack. We also show that there is a limit to how different the classical and quantum cases can be: the most probable key, given matching plain- and ciphertexts, has the same probability in both the quantum and the classical cases. We suggest an application of our results in the case where only a short secret key is available and the message is much longer.Comment: 19 pages, 2 figures. This is a revised version of an earlier version that appeared in the proc. of Eucrocrypt'04:LNCS3027, 200

Historical narratives as strategic resources: an analysis of the Turkish international contracting sector

The Turkish contracting sector has an enviable reputation for operating in high-risk international markets. The sector’s ability to respond to market instability could meaningfully be construed as sectoral-level capability. We aim to demonstrate how history can be mobilised in a formalised ‘strategy text’ to create a strategic narrative on the sectoral level. The Geography of Contractors as published by the Turkish Contractors Association (TCA) ostensively portrays the strategic development of Turkish international contractors over four decades. Such quasi-historical narratives are routinely mobilised for the purposes of creating a shared memory on the sectoral level. The chosen strategy text draws from multiple narrative fragments derived from past experience to generate a strategic agenda for the future. The representation given to multiple voices reflects the pluralistic nature of strategy making praxis. The overarching strategy narrative reflects a performative intent in legitimising some practices whilst discrediting others. Narrative analysis demonstrates the way in which actors, actions and events are positioned within a plot structure, with direct implications for the enactment of future strategic practices. The findings suggest that strategic actions can only ever be identified in retrospect, and that such arguments are always made with an eye on the future

HST observations of star clusters in NGC 1023: Evidence for three cluster populations?

Using HST images we have carried out a study of cluster populations in the nearby S0 galaxy NGC 1023. In two WFPC2 pointings we have identified 221 cluster candidates. The small distance (~9 Mpc) combined with deep F555W and F814W images allows us to reach about two magnitudes below the expected turn-over of the globular cluster luminosity function. NGC 1023 appears to contain at least three identifiable cluster populations: the brighter clusters show a clearly bimodal color distribution with peaks at V-I = 0.92 and at V-I = 1.15 and in addition there are a number of fainter, more extended objects with predominantly red colors. Among the brighter clusters, we find that the blue clusters have somewhat larger sizes than the red ones with mean effective radii of R(eff) ~ 2 and R(eff) ~ 1.7 pc, respectively. These clusters have luminosity functions (LFs) and sizes consistent with what is observed for globular clusters in other galaxies. Fitting Gaussians to the LFs of the blue and red compact clusters we find turn-over magnitudes of M(TO,blue)=-7.58 and M(TO,red)=-7.37 in V and dispersions of sigma(V,blue)=1.12 and sigma(V,red)=0.97. The fainter, more extended clusters have effective radii up to R(eff) ~ 10-15 pc and their LF appears to rise at least down to M(V) ~ -6, few of them being brighter than M(V) = -7. We suggest that these fainter objects may have a formation history distinct from that of the brighter GCs.Comment: 27 pages, 13 figures. Accepted for publication in the Astronomical Journa

Interval training normalizes cCardiomyocyte function, diastolic Ca²⁺ control, and SR Ca²⁺ release synchronicity in a mouse model of diabetic cardiomyopathy

In the present study we explored the mechanisms behind excitation-contraction (EC)-coupling defects in cardiomyocytes from mice with type-2 diabetes (db/db), and determined whether 13-weeks of aerobic interval training could restore cardiomyocyte Ca2+ cycling and EC-coupling. Reduced contractility in cardiomyocytes isolated from sedentary db/db was associated with increased diastolic sarcoplasmic reticulum (SR)-Ca2+ leak, reduced synchrony of Ca2+ release, reduced transverse (T)-tubule density, and lower peak systolic and diastolic Ca2+ and caffeine-induced Ca2+ release. Additionally, the rate of SR Ca2+ ATPase (SERCA2a)-mediated Ca2+ uptake during diastole was reduced, whereas a faster recovery from caffeine-induced Ca2+ release indicated increased Na+/Ca2+- exchanger (NCX) activity. The increased SR-Ca2+ leak was attributed to increased Ca2+-calmodulindependent protein kinase (CaMKIIδ) phosphorylation, supported by the normalization of SR-Ca2+ leak upon inhibition of CaMKIIδ (AIP). Exercise training restored contractile function associated with restored SR Ca2+ release synchronicity, T-tubule density, twitch Ca2+ amplitude, SERCA2a and NCX activities, and SR-Ca2+ leak. The latter was associated with reduced phosphorylation of cytosolic CaMKIIδ. Despite normal contractile function and Ca2+ handling after the training period, phospholamban was hyperphosphorylated at Serine-16. Protein kinase A (PKA) inhibition (H-89) in cardiomyocytes from the exercised db/db group abolished the differences in SR-Ca2+ load when compared with the sedentary db/db mice. EC-coupling changes were observed without changes in serum insulin or glucose levels, suggesting that the exercise training-induced effects are not via normalization of the diabetic condition. These data demonstrate that aerobic interval training almost completely restored the contractile function of the diabetic cardiomyocyte to levels close to sedentary wild type (WT)

Stark ionization of atoms and molecules within density functional resonance theory

We show that the energetics and lifetimes of resonances of finite systems under an external electric field can be captured by Kohn-Sham density functional theory (DFT) within the formalism of uniform complex scaling. Properties of resonances are calculated self-consistently in terms of complex densities, potentials, and wave functions using adapted versions of the known algorithms from DFT. We illustrate this new formalism by calculating ionization rates using the complex-scaled local density approximation and exact exchange. We consider a variety of atoms (H, He, Li, and Be) as well as the H2 molecule. Extensions are briefly discussed

On Probabilistic Applicative Bisimulation and Call-by-Value λ\lambda-Calculi (Long Version)

Probabilistic applicative bisimulation is a recently introduced coinductive methodology for program equivalence in a probabilistic, higher-order, setting. In this paper, the technique is applied to a typed, call-by-value, lambda-calculus. Surprisingly, the obtained relation coincides with context equivalence, contrary to what happens when call-by-name evaluation is considered. Even more surprisingly, full-abstraction only holds in a symmetric setting.Comment: 30 page

Magnetic ground state and magnon-phonon interaction in multiferroic h-YMnO3_3

Inelastic neutron scattering has been used to study the magneto-elastic excitations in the multiferroic manganite hexagonal YMnO$_3$. An avoided crossing is found between magnon and phonon modes close to the Brillouin zone boundary in the $(a,b)$-plane. Neutron polarization analysis reveals that this mode has mixed magnon-phonon character. An external magnetic field along the $c$-axis is observed to cause a linear field-induced splitting of one of the spin wave branches. A theoretical description is performed, using a Heisenberg model of localized spins, acoustic phonon modes and a magneto-elastic coupling via the single-ion magnetostriction. The model quantitatively reproduces the dispersion and intensities of all modes in the full Brillouin zone, describes the observed magnon-phonon hybridized modes, and quantifies the magneto-elastic coupling. The combined information, including the field-induced magnon splitting, allows us to exclude several of the earlier proposed models and point to the correct magnetic ground state symmetry, and provides an effective dynamic model relevant for the multiferroic hexagonal manganites.Comment: 12 pages, 10 figure

Optimal infinite scheduling for multi-priced timed automata

This paper is concerned with the derivation of infinite schedules for timed automata that are in some sense optimal. To cover a wide class of optimality criteria we start out by introducing an extension of the (priced) timed automata model that includes both costs and rewards as separate modelling features. A precise definition is then given of what constitutes optimal infinite behaviours for this class of models. We subsequently show that the derivation of optimal non-terminating schedules for such double-priced timed automata is computable. This is done by a reduction of the problem to the determination of optimal mean-cycles in finite graphs with weighted edges. This reduction is obtained by introducing the so-called corner-point abstraction, a powerful abstraction technique of which we show that it preserves optimal schedules

Metallic spin-glasses beyond mean-field: An approach to the impurity-concentration dependence of the freezing temperature

A relation between the freezing temperature ($T^{}_{\rm g}$) and the exchange couplings ($J^{}_{ij}$) in metallic spin-glasses is derived, taking the spin-correlations ($G^{}_{ij}$) into account. This approach does not involve a disorder-average. The expansion of the correlations to first order in $J^{}_{ij}/T^{}_{\rm g}$ leads to the molecular-field result from Thouless-Anderson-Palmer. Employing the current theory of the spin-interaction in disordered metals, an equation for $T^{}_{\rm g}$ as a function of the concentration of impurities is obtained, which reproduces the available data from {\sl Au}Fe, {\sl Ag}Mn, and {\sl Cu}Mn alloys well.Comment: 4 figures. This is a strongly revised version, where several aspects have been improved, and the equation for the freezing temperature has been refined. It is equivalent to the published version in J. Phys.: Condens. Matter 25 (2013) 13600

Electronic correlations on a metallic nanosphere

We consider the correlation functions in a gas of electrons moving within a thin layer on the surface of nanosize sphere. A closed form of expressions for the RKKY indirect exchange, superconducting Cooper loop and `density-density' correlation function is obtained. The systematic comparison with planar results is made, the effects of spherical geometry are outlined. The quantum coherence of electrons leads to the enhancement of all correlations for the points--antipodes on the sphere. This effect is lost when the radius of the sphere exceeds the temperature coherence length.Comment: 5 pages, no figures, to appear in PRB (RC