Top arXiv papers

• Topological nonsymmorphic crystalline superconductivity (TNCS) is an intriguing phase of matter, offering a platform to study the interplay between topology, superconductivity, and nonsymmorphic crystalline symmetries. Interestingly, some of TNCS are classified into $Z_4$ topological phases, which have unique surface states referred to as a Möbius strip or an hourglass, and have not been achieved in symmorphic superconductors. However, material realization of $Z_4$ TNCS has never been known, to the best of our knowledge. Here we propose that the paramagnetic superconducting phase of UCoGe under pressure is a promising candidate of $Z_4$-nontrivial TNCS enriched by glide symmetry. We evaluate $Z_4$ invariants of UCoGe by deriving the formulas relating $Z_4$ invariants to the topology of Fermi surfaces. Applying the formulas and previous ab-initio calculations, we clarify that three odd-parity representations, out of four, are $Z_4$-nontrivial TNCS, while the other is also $Z_2$-nontrivial TNCS. We also discuss possible $Z_4$ TNCS in CrAs and related materials.
• We show that strong parametric driving of a quantum harmonic oscillator coupled to a thermal bath allows one to distinguish between different microscopic models for the oscillator-bath coupling. We consider a bath with an Ohmic spectral density and a model where the system-bath interaction can be tuned continuously between position and momentum coupling via the coupling angle $\alpha$. We derive a master equation for the reduced density operator of the oscillator in Born-Markov approximation and investigate its quasi-steady state as a function of the driving parameters, the temperature of the bath and the coupling angle $\alpha$. We find that the time-averaged variance of position and momentum exhibits a strong dependence on these parameters. In particular, we identify parameter regimes that maximise the $\alpha$-dependence and provide an intuitive explanation of our results.
• Excitation functions were measured for the production of the 101,100Pd, 102m, 102g,101m,101g,100,99m,99gRh and 97Ru radionuclides by bombardment of 103Rh targets with proton beams up to 70 MeV, some of them for the first time. The new results are compared with the earlier experimental data and with the theoretical nuclear model code calculations from ALICE-IPPE, EMPIRE and TALYS 1.6. Thick target yields were deduced and possible application of the new data for production of medically relevant 101m,101gRh and 97Ru are discussed.
• Shallow trimers composed of three bosonic atoms in one-dimensional harmonic waveguides are studied in the vicinity of a Feshbach resonance. It is shown that for arbitrarily large values of the one-dimensional scattering length, an excited trimer branch exists in coexistence with the dimer and the trimer of the Lieb-Liniger model.
• A highly secure, foolproof, user authentication system is still a primary focus of research in the field of User Privacy and Security. Shoulder-surfing is an act of spying when an authorized user is logging into a system, and is promoted by a malicious intent of gaining unauthorized access. We present a gaze-assisted user authentication system as a potential solution to counter shoulder-surfing attacks. The system comprises of an eye tracker and an authentication interface with 12 pre-defined shapes (e.g., triangle, circle, etc.) that move simultaneously on the screen. A user chooses a set of three shapes as a password. To authenticate, the user follows the paths of three shapes as they move, one on each frame, over three consecutive frames. The system uses either the template matching or decision tree algorithms to match the scan-path of the user's gaze with the path traversed by the shape. The system was evaluated with seven users to test the accuracy of both the algorithms. We found that with the template matching algorithm the system achieves an accuracy of 95%, and with the decision tree algorithm an accuracy of 90.2%. We also present the advantages and disadvantages of using both the algorithms. Our study suggests that gaze-based authentication is a highly secure method against shoulder-surfing attacks as the unique pattern of eye movements for each individual makes the system hard to break into.
• Bosonic condensation of microcavity polaritons is accompanied by their relaxation from the ensemble of excited states into a single quantum state. The excess of energy is transferred to the crystal lattice that eventually involves heating of the structure. Creation of the condensate results in the local increase of the temperature which leads to the red shift of the exciton energy providing the mechanism for polariton self-trapping. By employing the driven-dissipative Gross-Pitaevskii model we predict a new type of a stable localized solution supported by the thermally-induced self-trapping in a one-dimensional microcavity structure. The predicted solution is of a sink-type i.e. it is characterized by the presence of converging density currents. We examine the spontaneous formation of these states from the white noise under spatially localized pumping and analyze the criteria for their stability. The collective bosonic polaron state described here may be considered as a toy model for studies of bosonic stars formed due to the self-gravity effect.
• We identify certain Gromov-Witten invariants counting rational curves with given incidence and tangency conditions with the Betti numbers of moduli spaces of point configurations in projective spaces. On the Gromov-Witten side, S. Fomin and G. Mikhalkin established a recurrence relation via tropicalization, which is realized on the moduli space side using Donaldson-Thomas invariants of subspace quivers.
• In the same way as tree rings give us useful information about the climate many decades ago (or even centuries ago in the case of big trees), population pyramids allow us to know birth or death rates several decades earlier. Naturally, they can fulfill such promises only if they have been recorded accurately. That is why we start this study by listing a number of pitfalls that may occur in the process of taking censuses. In this paper our main goal is to show how it is possible to "read" population pyramids. Sudden changes in birth rate give rise to the clearest signatures. This indicator reveals that major tragedies like famines, wars, or epidemics are generally accompanied by a fall in birth rates. Thanks to this observation, population pyramids can be used to identify and gauge the blows suffered by populations and nations. As an illustration of how this works, we compare the population pyramids of North and South Korea. This allows us, among other things, to gauge the scale of the food shortage that North Korea experienced at the end of the 1990s.
• Activation cross sections of the natLa(p,x)139,137m,137g,135,134,133mCe, natLa(p,x)135,134,133La and 133m,133g,131Ba nuclear reactions have been measured experimentally, for the first time (except 139Ce). Cross-sections in the 34-64 MeV energy range were obtained through an activation method combining the stacked foil irradiation technique and gamma-ray spectrometry. The experimental cross sections were compared with the theoretical prediction in the TENDL-2014 and TENDL-2015, TALYS based libraries. Applications in the field of medical radionuclides production is discussed.
• We report a measurement of time-dependent $CP$ violation parameters in ${B^0 \to K_S^0 \eta \gamma}$ decays. The study is based on a data sample, containing ${772 \times 10^6 B\bar{B}}$ pairs, that was collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We obtain the $CP$ violation parameters of ${{\cal S} = -1.32 \pm 0.77 {\rm (stat.)} \pm 0.36{\rm (syst.)}}$ and ${{\cal A} = -0.48 \pm 0.41 {\rm (stat.)} \pm 0.07{\rm (syst.)}}$ for the invariant mass of the $K_S^0 \eta$ system up to 2.1 GeV/$c^2$.
• In this paper, we propose a cross layer energy efficient resource allocation and remote radio head (RRH) selection algorithm for heterogeneous traffic in power domain - non-orthogonal multiple access (PD-NOMA) based heterogeneous cloud radio access networks (H-CRANs). The main aim is to maximize the EE of the elastic users subject to the average delay constraint of the streaming users and the constraints, RRH selection, subcarrier, transmit power and successive interference cancellation. The considered optimization problem is non-convex, NP-hard and intractable. To solve this problem, we transform the fractional objective function into a subtractive form. Then, we utilize successive convex approximation approach. Moreover, in order to increase the processing speed, we introduce a framework for accelerating the successive convex approximation for low complexity with the Lagrangian method on graphics processing unit. Furthermore, in order to show the optimality gap of the proposed successive convex approximation approach, we solve the proposed optimization problem by applying an optimal method based on the monotonic optimization. Studying different scenarios show that by using both PD-NOMA technique and H-CRAN, the system energy efficiency is improved.
• Excitation functions were measured for the natSr(d,x)88,87m,87g,86g,85gY, 87m,85g,83g,82Sr, 86g,84g,83,82m, 81gRb reactions by the stacked foil activation technique and high-resolution gamma-spectrometry up to 50 MeV. We present the first experimental activation cross section data for all investigated reactions. Our experimental data are compared with the TALYS code results as available in the TENDL-2015 on-line library. Use of deuteron induced reactions on Sr for production of medical isotopes is discussed.
• Measurement results for millimeter wave LOS MIMO systems are presented with a focus on time variation and multipath propagation. Different system setups are used, including 2x2 and 3x3 MIMO, and involving different synchronization procedures and front-ends. Furthermore, different propagation scenarios are evaluated, covering a wide area of applications. The results show that the LOS component carries significantly more power than the NLOS components, and that frequency selectivity from front-ends should be taken into account when designing these high bandwidth systems. Frequency offsets and other phase variations due to transmit and receive oscillator differences are treated as part of the channel and thus, depending on the synchronization setup, the MIMO system exhibits different time variations, particularly in the case of independent local oscillators. It is also observed that these systems experience significant non-trivial long-term variations in terms of amplitude and phase.
• We consider the Hall conductivity of composite fermions in the presence of quenched disorder using the non-relativistic theory of Halperin, Lee and Read (HLR). Consistent with the recent analysis of Wang et al., we show that in a fully quantum mechanical transport calculation, the HLR theory, under suitable assumptions, exhibits a Hall response $\sigma_{xy}^{\rm CF} = - {1 \over 2} {e^2 \over h}$ that is consistent with an emergent particle-hole symmetric electrical response. Remarkably, this response of the HLR theory remains robust even when the disorder range is of the order of the Fermi wavelength.
• Experimental cross sections are presented for the 159Tb(p,xn)153,155,157,159Dy, 152,153,155,156m2,m1,g,158Tb and 153,151Gd nuclear reactions up to 65 MeV. The experimental results are compared with the recently reported experimental data and with the results of the nuclear reaction codes ALICE-IPPE, EMPIRE and TALYS as reported in the TENDL-2015 on-line library. Integral thick-target yields are also derived for the reaction products used in practical applications and production routes are discussed.
• In order to effectively improve the output quality of X-ray free electron laser (XFEL), we theoretically propose an XFEL scheme seeded by atomic inner-shell laser. As well known, an atomic inner-shell laser based on neutral atoms and pumped by an XFEL has been experimentally demonstrated, which produced sub-femtosecond X-ray pulses with increased temporal coherence. It shows that, by using the inner-shell laser as a seed to modulate the electron bunch, very stable and almost fully-coherent short-wavelength XFEL pulses can be generated. The proposed scheme holds promising prospects in X-ray wavelengths, and even shorter.
• Two key contributions presented in this paper are: i) A method for building a dataset containing source code features extracted from source files taken from Open Source Software (OSS) and associated bug reports, ii) A predictive model for estimating defectiveness of a given source code. These artifacts can be useful for building tools and techniques pertaining to several automated software engineering areas such as bug localization, code review, and recommendation and program repair. In order to achieve our goal, we first extract coding style information (e.g. related to programming language constructs used in the source code) for source code files present on GitHub. Then the information available in bug reports (if any) associated with these source code files are extracted. Thus fetched un(/ semi)-structured information is then transformed into a structured knowledge base. We considered more than 30400 source code files from 20 different GitHub repositories with about 14950 associated bug reports across 4 bug tracking portals. The source code files considered are written in four programming languages (viz., C, C++, Java, and Python) and belong to different types of applications. A machine learning (ML) model for estimating the defectiveness of a given input source code is then trained using the knowledge base. In order to pick the best ML model, we evaluated 8 different ML algorithms such as Random Forest, K Nearest Neighbour and SVM with around 50 parameter configurations to compare their performance on our tasks. One of our findings shows that best K-fold (with k=5) cross-validation results are obtained with the NuSVM technique that gives a mean F1 score of 0.914.
• The Gaussian width is a fundamental quantity in probability, statistics and geometry, known to underlie the intrinsic difficulty of estimation and hypothesis testing. In this work, we show how the Gaussian width, when localized to any given point of an ellipse, can be controlled by the Kolmogorov width of a set similarly localized. This connection leads to an explicit characterization of the estimation error of least-squares regression as a function of the true regression vector within the ellipse. The rate of error decay varies substantially as a function of location: as a concrete example, in Sobolev ellipses of smoothness $\alpha$, we exhibit rates that vary from $(\sigma^2)^{\frac{2 \alpha}{2 \alpha + 1}}$, corresponding to the classical global rate, to the faster rate $(\sigma^2)^{\frac{4 \alpha}{4 \alpha + 1}}$. We also show how the local Kolmogorov width can be related to local metric entropy.
• An important consequence of the theory of entropy of Z-actions is that the events measurable with respect to the far future coincide (modulo null sets) with those measurable with respect to the distant past, and that measuring the entropy using the past will give the same value as measuring it using the future. In this paper we show that for measures invariant under multiparameter algebraic actions if the entropy attached to coarse Lyapunov foliations fail to display a stronger symmetry property of a similar type this forces the measure to be invariant under non-trivial unipotent groups. Some consequences of this phenomenon are noted.
• We establish the existence of Kähler-Ricci flow on pseudoconvex domains with general initial metric without curvature bounds. Moreover we prove that this flow is simultaneously complete, and its normalized version converge to the complete Kähler-Einstein metric, which generalizes Topping's works on surfaces.
• In the frame of a systematical study of light ion induced nuclear reactions on platinum, activation cross sections for deuteron induced reactions were investigated. Excitation functions were measured in the 20.8 - 49.2 MeV energy range for the natPt(d,xn)191,192,193,194,195,196m2,196g,198g,199Au, natPt(d,x)188,189,191,195m,197m,197gPt and natPt(d,x)189,190,192,194m2Ir reactions by using the stacked foil irradiation technique. The experimental results are compared with previous results from the literature and with the theoretical predictions in the TENDL-2014 and TENDL-2015 libraries. The applicability of the produced radio-tracers for wear measurements has been presented.
• Temporal variations in the Suns internal velocity field with a periodicity of about 11 years have been observed over the last four decades. The period of these torsional oscillations and their latitudinal propagation roughly coincides with the period and equatorward propagation of sunspots which originate from a magnetohydrodynamic dynamo mechanism operating in the Suns interior. While the solar differential rotation plays an important role in this dynamo mechanism by inducting the toroidal component of magnetic field, the impact of torsional oscillations on the dynamo mechanism and hence the solar cycle is not well understood. Here, we include the observed torsional oscillations into a flux transport dynamo model of the solar cycle to investigate their effect. We find that the overall amplitude of the solar cycle does not change significantly on inclusion of torsional oscillations. However, all the characteristics of the Waldmeier effect in the sunspot cycle are qualitatively reproduced by varying only the amplitude of torsional oscillations. The Waldmeier effect, first noted in 1935, includes the important characteristic that the amplitude of sunspot cycles is anti-correlated to their rise time; cycles with high initial rise rate tend to be stronger. This has implications for solar cycle predictions. Our results suggest that the Waldmeier effect could be a plausible outcome of cycle to cycle modulation of torsional oscillations and provides a physical basis for sunspot cycle forecasts based on torsional oscillation observations. We also provide a theoretical explanation based on the magnetic induction equation thereby connecting two apparently disparate phenomena.
• Establishment of a new technique or extension of an existing technique for thermal and thermoelectric measurements to a more challenging system is an important task to explore the thermal and thermoelectric properties of various materials and systems. The bottleneck lies in the challenges in measuring the thermal contact resistance. In this work, we applied electron beam self-heating technique to derive the intrinsic thermal conductivity of suspended Molybdenum Disulfide (MoS2) ribbons and the thermal contact resistance, with which the interfacial thermal resistance between few-layer MoS2 and Pt electrodes was calculated. The measured room temperature thermal conductivity of MoS2 is around 30 W/mK, while the estimated interfacial thermal resistance is around 2*10-6 m2K/W. Our experiments extend a useful branch in application of this technique for studying thermal properties of suspended layered ribbons and have potential application in investigating the interfacial thermal resistance of different 2D heterojunctions.
• In this paper, we consider the nodal set of a bi-harmonic function $u$ on an $n$ dimensional $C^{\infty}$ Riemannian manifold $M$, that is, $u$ satisfies the equation $\triangle_M^2u=0$ on $M$, where $\triangle_M$ is the Laplacian operator on $M$. We first define the frequency function and the doubling index for the bi-harmonic function $u$, and then establish their monotonicity formulae and doubling conditions. With the help of the smallness propagation and partitions, we show that, for some ball $B_r(x_0)\subseteq M$ with $r$ small enough, an upper bound for the measure of nodal set of the bi-harmonic function $u$ can be controlled by $N^\alpha$, that is, \mathcalH^n-1\left(\left{x∈B_r/2(x_0)|u(x)=0\right}\right)≤CN^\alphar^n-1, where $N=\max\left\{C_0,N(x_0,r)\right\}$, $\alpha$, $C$ and $C_0$ both are positive constants depending only on $n$ and $M$. Here $N(x_0,r)$ is the frequency function of $u$ centered at $x_0$ with radius $r$. Furthermore, we derive that an upper measure for nodal sets of eigenfunctions of the bi-harmonic operator on a $C^{\infty}$ compact Riemannian manifold without boundary can be controlled by $\lambda^\beta$ for the corresponding eigenvalue $\lambda^2$ and some positive constant $\beta$.
• The mass of axion dark matter is only weakly bounded by cosmological observations, necessitating a variety of detection techniques and experiments at many different mass ranges. Axions are expected to couple to photons via the inverse Primakoff effect and cryogenic resonant cavities are often proposed as a tool for detecting these photons. However, such structures are inherently narrowband and the range of possible axion dark matter masses spans several orders of magnitude. On the other hand broadband low-mass particle haloscopes have been proposed using inductive magnetometer sensors coupled to SQUID amplifiers and requiring a solenoid magnet of gapped toroidal geometry. In this work we propose an alternative approach, which uses a capacitive sensor in a conventional solenoidal magnet with the magnetic field aligned in the laboratory z-axis, as implemented in standard haloscope experiments. In the presence of a large DC magnetic field, the inverse Primakoff effect causes a time varying electric field (or displacement current) in the z-direction to oscillate at the axion Compton frequency. We propose non-resonant techniques to detect this electric field by implementing capacitive sensors coupled to a low noise amplifier. We present the theoretical foundation for this proposal, and the first experimental results. Preliminary results constrain $g_{a\gamma\gamma} >\sim2.35\times10^{-12}$ $\text{GeV}^{-1}$ in the mass range of $2.08\times10^{-11}$ to $2.2\times10^{-11}$ eV, and demonstrate potential sensitivity to axion like dark matter with masses in the range of $10^{-12}$ to $10^{-8}$ eV.
• In this paper, the notion of generic transversality and its characterization are given. The characterization is also a further improvement of the basic transversality result and its strengthening which was given by John Mather.
• Excitation functions were measured for the $^{nat}$Ag(d,x)$^{105,104}$Cd, $^{110m,108m,106m,105g,104g}$Ag and $^{101}$Pd, $^{105,101m}$Rh reactions over the energy range 33 50 MeV by using the stacked foil activation technique and subsequent high-resolution gamma spectrometry. We present the first experimental cross section data above 40 MeV for all of these reactions and the first experimental cross section data for $^{nat}$Ag(d,x)$^{108m,104g}$Ag and $^{105,103}$Rh. The experimental data are compared with results of the model calculations performed with the ALICE D, EMPIRE D theoretical nuclear reaction model codes and with the TALYS code results as available in the TENDL2014 and 2015 on-line libraries.
• Additional experimental cross sections were deduced for the long half-life activation products (172Hf and 173Lu) from the alpha particle induced reactions on ytterbium up to 38 MeV from late, long measurements and for 175Yb, 167Tm from a re-evaluation of earlier measured spectra. The cross-sections are compared with the earlier experimental datasets and with the data based on the TALYS theoretical nuclear reaction model (available in the TENDL-2014 and 2015 libraries) and the ALICE-IPPE code.
• We demonstrate an ultrabright narrow-band two-photon source at the 1.5 -\mu m telecom wavelength for long-distance quantum communication. By utilizing a bow-tie cavity, we obtain a cavity enhancement factor of $4.06\times 10^4$. Our measurement of the second-order correlation function $G^{(2)} ({\tau})$ reveals that the linewidth of $2.4$ MHz has been hitherto unachieved in the 1.5 -\mu m telecom band. This two-photon source is useful for obtaining a high absorption probability close to unity by quantum memories set inside quantum repeater nodes. Furthermore, to the best of our knowledge, the observed spectral brightness of $3.94\times 10^5$ pairs/(s$\cdot$MHz$\cdot$mW) is also the highest reported over all wavelengths.
• We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e+e- pairs observed in the excited Be-8 nucleus decays. Due to its coupling to electrons, the X could be produced in the bremsstrahlung reaction e- Z -> e- Z X by a 100 GeV e- beam incident on an active target in the NA64 experiment at the CERN SPS and observed through the subsequent decay into a e+e- pair. With 5.4\times 10^10 electrons on target, no evidence for such decays was found, allowing to set first limits on the X-e^- coupling in the range 1.3\times 10^-4≲\epsilon_e ≲4.2\times 10^-4 excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A') from non-observation of the decay A'->e+e- of the bremsstrahlung A' with a mass ≲23 MeV.
• Weak value amplification has been applied to various small physical quantities estimation, however there still lacks a practical feasible protocol to amplify ultra-small longitudinal phase, which is of importance in high precision measurement. Very recently, a different amplification protocol within the framework of weak measurements is proposed to solve this problem, which is capable of measuring any ultra-small longitudinal phase signal that conventional interferometry tries to do. Here we experimentally demonstrate this weak measurements amplification protocol of ultra-small longitudinal phase and realize one order of magnitude amplification in the same technical condition, which verifies the validity of the protocol and show higher precision and sensitivity than conventional interferometry. Our results significantly broaden the area of applications of weak measurements and may play an important role in high precision measurements.
• We present hydrodynamical N-body models which demonstrate that elliptical galaxies can transform into S0s by acquiring a disc. In particular, we show that the merger with a massive gas-rich satellite can lead to the formation of a baryonic disc around an elliptical. We model the elliptical as a massive, compact galaxy which could be observed as a 'red nugget' in the high-z universe. This scenario contrasts with existing S0 formation scenarios in the literature in two important ways. First, the progenitor is an elliptical galaxy whereas scenarios in the literature typically assume a spiral progenitor. Second, the physical conditions underlying our proposed scenario can exist in low-density environments such as the field, in contrast to scenarios in the literature which typically address dense environments like clusters and groups. As a consequence, S0s in the field may be the most likely candidates to have evolved from elliptical progenitors. Our scenario also naturally explains recent observations which indicate that field S0s may have older bulges than discs, contrary to cluster S0s which seem to have older discs than bulges.
• Mar 22 2018 math.OC arXiv:1803.07744v1
This paper investigates an energy conservation and dissipation -- passivity -- aspect of dynamic models in evolutionary game theory. We define a notion of passivity using the state-space representation of the models, and we devise systematic methods to examine passivity and to identify properties of passive dynamic models. Based on the methods, we describe how passivity is connected to stability in population games and illustrate stability of passive dynamic models using numerical simulations.
• Reinforcement learning based adaptive/approximate dynamic programming (ADP) is a powerful technique to determine an approximate optimal controller for a dynamical system. These methods bypass the need to analytically solve the nonlinear Hamilton-Jacobi-Bellman equation, whose solution is often to difficult to determine but is needed to determine the optimal control policy. ADP methods usually employ a policy iteration algorithm that evaluates and improves a value function at every step to find the optimal control policy. Previous works in ADP have been lacking a stronger condition that ensures the convergence of the policy iteration algorithm. This paper provides a sufficient but not necessary condition that guarantees the convergence of an ADP algorithm. This condition may provide a more solid theoretical framework for ADP-based control algorithm design for nonlinear dynamical systems.
• New experimental excitation functions for proton induced reactions on natW are presented in the 32- 65 MeV energy range. The cross sections for natW(p,xn)186,184,183,182m,182g,181Re, naW(p,x)178W, natW(p,x)183,182,180m,177,176,175Ta, 175Hf, 177Lu were measured via an activation method by using a stacked-foil irradiation technique and high resolution gamma-ray spectrometry. The results were compared with predicted values obtained with the nuclear reaction model code TALYS (results taken from TENDL-2014 and TENDL-2015 on-line library). Production routes of the medically relevant radionuclides 186Re, 178W 178Ta and 181W are discussed.
• HD 176465 is a binary system whose both components are solar-like pulsators and whose oscillation frequencies were observed by the \kepler mission. In this paper we have modeled the asteroseismic and spectroscopic data of the stars, and have determined their convection-zone helium abundances using the signatures left by the He\sc ii ionization zone on the mode frequencies. As expected we find that the components of the binary have the same age within uncertainties ($3.087 \pm 0.580$ Gyr and $3.569 \pm 0.912$ Gyr); they also have the same initial helium abundance (Y$_{\mathrm{init}}$=0.253 $\pm$ 0.006 and 0.254 $\pm$ 0.008). Their current metallicity ([Fe/H]=$-0.275 \pm 0.04$ and $-0.285 \pm 0.04$) is also the same within errors. Fits to the signature of the He\sc ii acoustic glitch yields current helium abundances of $Y_{\rm A} = 0.224 \pm 0.006$ and $Y_{\rm B} = 0.233 \pm 0.008$ for the two components. Analyzing the complete ensemble of models generated for this investigation we find that both the amplitude and acoustic depth of the glitch signature arising from the second helium ionization zone and the base of the convection zone (CZ) are functions of mass. We show that the acoustic depths of these glitches are positively correlated with each other. The analysis can help us to detect the internal structure and constrain the chemical compositions.
• Mar 22 2018 math.DG arXiv:1803.07733v1
Qualitative behavior of Bach flow is established on compact four-dimensional locally homogeneous product manifolds. This is achieved by lifting to the homogeneous universal cover and, in most cases, capitalizing on the resultant group structure. The resulting system of ordinary differential equations is carefully analyzed on a case-by-case basis, with explicit solutions found in some cases. Limiting behavior of the metric and the curvature are determined in all cases. The behavior on quotients of $\mathbb{R} \times \mathbb{S}^3$ proves to be the most challenging and interesting.
• In this paper, we study convergence and superconvergence theory of integer and fractional derivatives of the one-point and the two-point Hermite interpolations. When considering the integer-order derivative, exponential decay of the error is proved, and superconvergence points are located, at which the convergence rates are $O(N^{-2})$ and $O(N^{-1.5})$, respectively, better than the global rate for the one-point and two-point interpolations. Here $N$ represents the degree of interpolation polynomial. It is proved that the $\alpha$-th fractional derivative of $(u-u_N)$ with $k<\alpha<k+1$, is bounded by its $(k+1)$-th derivative. Furthermore, the corresponding superconvergence points are predicted for fractional derivatives, and an eigenvalue method is proposed to calculate the superconvergence points for the Riemann-Liouville fractional derivative. In the application of the knowledge of superconvergence points to solve FDEs, we discover that a modified collocation method makes numerical solutions much more accurate than the traditional collocation method.
• Considering the expensive radio frequency (RF) chain, huge training overhead and feedback burden issues in massive MIMO, in this letter, we propose a mixed-timescale per-group hybrid precoding (MPHP) scheme under an adaptive partially-connected RF precoding structure (PRPS), where the RF precoder is implemented using an adaptive connection network (ACN) and M analog phase shifters (APSs), where M is the number of antennas at the base station (BS). Exploiting the mixed-time stage channel state information (CSI) structure, the joint-design of ACN and APSs is formulated as a statistical signal-to-leakage-and-noise ratio (SSLNR) maximization problem, and a heuristic group RF precoding (GRFP) algorithm is proposed to provide a near-optimal solution. Simulation results show that the proposed design advances at better energy efficiency (EE) and lower hardware cost, CSI signaling overhead and computational complexity than the conventional hybrid precoding (HP) schemes.
• We introduce a family of sequence transformations, defined via partial Bell polynomials, that may be used for a systematic study of a wide variety of problems in enumerative combinatorics. This family includes some of the transformations listed in the paper by Bernstein & Sloane, now seen as transformations under the umbrella of partial Bell polynomials. Our goal is to describe these transformations from the algebraic and combinatorial points of view. We provide functional equations satisfied by the generating functions, derive inverse relations, and give a convolution formula. While the full range of applications remains unexplored, in this paper we show a glimpse of the versatility of Bell transformations by discussing the enumeration of several combinatorial configurations, including rational Dyck paths, rooted planar maps, and certain classes of permutations.
• We approximate the backward reachable set of discrete-time autonomous polynomial systems using the recently developed occupation measure approach. We formulate the problem as an infinite-dimensional linear programming (LP) problem on measures and its dual on continuous functions. Then we approximate the LP by a hierarchy of finite-dimensional semidefinite programming (SDP) programs on moments of measures and their duals on sums-of-squares polynomials. Finally we solve the SDP's and obtain a sequence of outer approximations of the backward reachable set. We demonstrate our approach on three dynamical systems. As a special case, we also show how to approximate the preimage of a compact semi-algebraic set under a polynomial map.
• In this paper we outline the construction of semiclassical eigenfunctions of integrable models in terms of the semiclassical path integral for the Poisson sigma model with the target space being the phase space of the integrable system. The semiclassical path integral is defined as a formal power series with coefficients being Feynman diagrams. We also argue that in a similar way one can obtain irreducible semiclassical representations of Kontsevich's star product.
• This paper studies the portfolio optimization problem when the investor's utility is general and the return and volatility of the risky asset are fast mean-reverting, which are important to capture the fast-time scale in the modeling of stock price volatility. Motivated by the heuristic derivation in [J.-P. Fouque, R. Sircar and T. Zariphopoulou, \emphMathematical Finance, 2016], we propose a zeroth order strategy, and show its asymptotic optimality within a specific (smaller) family of admissible strategies under proper assumptions. This optimality result is achieved by establishing a first order approximation of the problem value associated to this proposed strategy using singular perturbation method, and estimating the risk-tolerance functions. The results are natural extensions of our previous work on portfolio optimization in a slowly varying stochastic environment [J.-P. Fouque and R. Hu, \emphSIAM Journal on Control and Optimization, 2017], and together they form a whole picture of analyzing portfolio optimization in both fast and slow environments.
• The solutions for the Tolmann-Oppenheimer-Volkoff (TOV) equation bring valuable informations about the macroscopical features of compact astrophysical objects. They are sensitive to both the equation of state considered for nuclear matter and the background gravitational theory. In this work we construct the TOV equation for a conservative version of the $f(R,T)$ gravity. While the non-vanishing of the covariant derivative of the $f(R,T)$ energy-momentum tensor yields, in a cosmological perspective, the prediction of creation of matter throughout the universe evolution as shown by T. Harko, in the analysis of the hydrostatic equilibrium of compact astrophysical objects, this property still lacks a convincing physical explanation. The imposition of $\nabla^{\mu}T_{\mu\nu}=0$ demands a particular form for the function $h(T)$ in $f(R,T)=R+h(T)$, which is here derived. We construct and solve the TOV equation for this case and the macroscopical properties of compact stars, derived within this approach, are presented and discussed.
• This paper describes Infosys's participation in the "2nd Social Media Mining for Health Applications Shared Task at AMIA, 2017, Task 2". Mining social media messages for health and drug related information has received significant interest in pharmacovigilance research. This task targets at developing automated classification models for identifying tweets containing descriptions of personal intake of medicines. Towards this objective we train a stacked ensemble of shallow convolutional neural network (CNN) models on an annotated dataset provided by the organizers. We use random search for tuning the hyper-parameters of the CNN and submit an ensemble of best models for the prediction task. Our system secured first place among 9 teams, with a micro-averaged F-score of 0.693.
• High-dimensional variable selection in the proportional hazards (PH) model has many successful applications in different areas. In practice, data may involve confounding variables that do not satisfy the PH assumption, in which case the stratified proportional hazards (SPH) model can be adopted to control the confounding effects by stratification of the confounding variable, without directly modeling the confounding effects. However, there is lack of computationally efficient statistical software for high-dimensional variable selection in the SPH model. In this work, an R package, SurvBoost, is developed to implement the gradient boosting algorithm for fitting the SPH model with high-dimensional covariate variables and other confounders. Extensive simulation studies demonstrate that in many scenarios SurvBoost can achieve a better selection accuracy and reduce computational time substantially compared to the existing R package that implements boosting algorithms without stratification. The proposed R package is also illustrated by an analysis of the gene expression data with survival outcome in The Cancer Genome Atlas (TCGA) study. In addition, a detailed hands-on tutorial for SurvBoost is provided.
• We address the interplay between dimension and quantum anomaly on the breathing mode frequency of a strongly interacting Fermi gas harmonically trapped at zero temperature. Using a beyond mean-field, Gaussian pair fluctuation theory, we employ periodic boundary conditions to simulate the dimensionality of the system and impose a local density approximation, with two different schemes, to model different trapping potentials in the tightly-confined axial direction. By using a sum-rule approach, we compute the breathing mode frequency associated with a small variation of the trapping frequency along the weakly-confined transverse direction, and describe its behavior as functions of the dimensionality, from two- to three-dimensions, and of the interaction strength. We compare our predictions with previous calculations on the two-dimensional breathing mode anomaly and discuss their possible observation in ultracold Fermi gases of $^{6}$Li and $^{40}$K atoms.
• The robust beamforming problem in multiple-input single-output (MISO) downlink networks of simultaneous wireless information and power transfer (SWIPT) is studied in this paper. Adopting the time switching fashion to perform energy harvesting and information decoding respectively, we aim at maximizing the sum rate under imperfect channel state information (CSI) and the chance constraints of users' harvested energy. In view of the fact that the constraints for minimal harvested energy is not necessary to meet from time to time, this paper adopts chance constraint to model it and uses the Bernstein inequality to transform it into deterministic constraints equivalently. Recognizing the maximum sum rate problem of imperfect CSI as nonconvex problem, we transform it into finding the expectation of minimum mean square error (MMSE) equivalently in this paper, and an alternative optimization (AO) algorithm is proposed to decompose the optimization problem into two sub-problems: the transmit beamformer design and the division of switching time. The simulation results show the performance gains compared to non-robust state of the art schemes.
• Modern scientific computational methods are undergoing a transformative change; big data and statistical learning methods now have the potential to outperform the classical first-principles modeling paradigm. This book bridges this transition, connecting the theory of probability, stochastic processes, functional analysis, numerical analysis, and differential geometry. It describes two classes of computational methods to leverage data for modeling dynamical systems. The first is concerned with data fitting algorithms to estimate parameters in parametric models that are postulated on the basis of physical or dynamical laws. The second class is on operator estimation, which uses the data to nonparametrically approximate the operator generated by the transition function of the underlying dynamical systems. This self-contained book is suitable for graduate studies in applied mathematics, statistics, and engineering. Carefully chosen elementary examples with supplementary MATLAB codes and appendices covering the relevant prerequisite materials are provided, making it suitable for self-study.
• The relativistic quantum decay laws of moving unstable particles are analyzed for a general class of mass distribution densities which behave as power laws near the (non-vanishing) lower bound $\mu_0$ of the mass spectrum. The survival probability $\mathcal{P}_p(t)$, the instantaneous mass $M_p(t)$ and the instantaneous decay rate $\Gamma_p(t)$ of the moving unstable particle are evaluated over short and long times for an arbitrary value $p$ of the (constant) linear momentum. The ultrarelativistic and non-relativistic limits are studied. Over long times, the survival probability $\mathcal{P}_p(t)$ is approximately related to the survival probability at rest $\mathcal{P}_0(t)$ by a scaling law. The scaling law can be interpreted as the effect of the relativistic time dilation if the asymptotic value $M_p\left(\infty\right)$ of the instantaneous mass is considered as the effective mass of the unstable particle over long times. The effective mass has magnitude $\mu_0$ at rest and moves with linear momentum $p$ or, equivalently, with constant velocity $1\Big/\sqrt{1+\mu_0^2\big/p^2}$. The instantaneous decay rate $\Gamma_p(t)$ is approximately independent of the linear momentum $p$, over long times, and, consequently, is approximately invariant by changing reference frame.

Luis Cruz Mar 16 2018 15:34 UTC

Related Work:

- [Performance-Based Guidelines for Energy Efficient Mobile Applications](http://ieeexplore.ieee.org/document/7972717/)
- [Leafactor: Improving Energy Efficiency of Android Apps via Automatic Refactoring](http://ieeexplore.ieee.org/document/7972807/)

Dan Elton Mar 16 2018 04:36 UTC

Code is open source and available at :
[https://github.com/delton137/PIMD-F90][1]

[1]: https://github.com/delton137/PIMD-F90

Danial Dervovic Mar 01 2018 12:08 UTC

Hello again Māris, many thanks for your patience. Your comments and questions have given me much food for thought, and scope for an amended version of the paper -- please see my responses below.

Please if any of the authors of [AST17 [arXiv:1712.01609](https://arxiv.org/abs/1712.01609)] have any fu

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igorot Feb 28 2018 05:19 UTC

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[1]: https://www.igorotage.com/

Beni Yoshida Feb 13 2018 19:53 UTC

This is not a direct answer to your question, but may give some intuition to formulate the problem in a more precise language. (And I simplify the discussion drastically). Consider a static slice of an empty AdS space (just a hyperbolic space) and imagine an operator which creates a particle at some

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Abhinav Deshpande Feb 10 2018 15:42 UTC

I see. Yes, the epsilon ball issue seems to be a thorny one in the prevalent definition, since the gate complexity to reach a target state from any of a fixed set of initial states depends on epsilon, and not in a very nice way (I imagine that it's all riddled with discontinuities). It would be inte

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Elizabeth Crosson Feb 10 2018 05:49 UTC

Thanks for the correction Abhinav, indeed I meant that the complexity of |psi(t)> grows linearly with t.

Producing an arbitrary state |phi> exactly is also too demanding for the circuit model, by the well-known argument that given any finite set of gates, the set of states that can be reached i

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Abhinav Deshpande Feb 09 2018 20:21 UTC

Elizabeth, interesting comment! Did you mean to say that the complexity of $U(t)$ increases linearly with $t$ as opposed to exponentially?

Also, I'm confused about your definition. First, let us assume that the initial state is well defined and is $|\psi(0)\rangle$.
If you define the complexit

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Elizabeth Crosson Feb 08 2018 04:27 UTC

The complexity of a state depends on the dynamics that one is allowed to use to generate the state. If we restrict the dynamics to be "evolving according a specific Hamiltonian H" then we immediately have that the complexity of U(t) = exp(i H t) grows exponentially with t, up until recurrences that

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Danial Dervovic Feb 05 2018 15:03 UTC

Thank you Māris for the extremely well thought-out and articulated points here.

I think this very clearly highlights the need to think explicitly about the precompute time if using the lifting to directly simulate the quantum walk, amongst other things.

I wish to give a well-considered respons

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