A. Stephen Morse

A. Stephen Morse
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A. Stephen Morse

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Pub Categories

Mathematics - Optimization and Control (5)
Computer Science - Multiagent Systems (4)
Earth and Planetary Astrophysics (4)
Computer Science - Distributed; Parallel; and Cluster Computing (3)
Mathematics - Combinatorics (2)
General Relativity and Quantum Cosmology (2)
High Energy Physics - Experiment (1)
High Energy Physics - Phenomenology (1)
Mathematics - Dynamical Systems (1)
High Energy Astrophysical Phenomena (1)
Mathematics - Numerical Analysis (1)
Physics - Physics and Society (1)
Instrumentation and Methods for Astrophysics (1)
Computer Science - Numerical Analysis (1)
High Energy Physics - Theory (1)
Nonlinear Sciences - Chaotic Dynamics (1)

Publications Authored By A. Stephen Morse

A distributed algorithm is described for finding a common fixed point of a family of m>1 nonlinear maps M_i : R^n -> R^n assuming that each map is a paracontraction and that at least one such common fixed point exists. The common fixed point is simultaneously computed by m agents assuming each agent i knows only M_i, the current estimates of the fixed point generated by its neighbors, and nothing more. Each agent recursively updates its estimate of a fixed point by utilizing the current estimates generated by each of its neighbors. Read More

Motivated by the problem of determining unknotted routes for the scaffolding strand in DNA origami self-assembly, we examine existence and knottedness of A-trails in graphs embedded on the torus. We show that any A-trail in a checkerboard-colorable torus graph is unknotted and characterize the existence of A-trails in checkerboard-colorable torus graphs in terms of pairs of quasitrees in associated embeddings. Surface meshes are frequent targets for DNA nanostructure self-assembly, and so we study both triangular and rectangular torus grids. Read More

The Rosetta lander Philae successfully landed on the nucleus of comet 67P/Churyumov-Gerasimenko on 12 November 2014. Philae is equipped with two gas analyzers: The Cometary Sampling and Composition experiment (COSAC) and the gas chromatograph and mass spectrometer Ptolemy. On 12 to 14 November 2014 both instruments measured the organic composition of the comet nucleus material through seven measurements in sniffing mode during Philae's hopping and at its final landing site Abydos. Read More

In a recent paper, a distributed algorithm was proposed for solving linear algebraic equations of the form $Ax = b$ assuming that the equation has at least one solution. The equation is presumed to be solved by $m$ agents assuming that each agent knows a subset of the rows of the matrix $[A \; b]$, the current estimates of the equation's solution generated by each of its neighbors, and nothing more. Neighbor relationships are represented by a time-dependent directed graph $N(t)$ whose vertices correspond to agents and whose arcs characterize neighbor relationships. Read More

By the distributed averaging problem is meant the problem of computing the average value of a set of numbers possessed by the agents in a distributed network using only communication between neighboring agents. Gossiping is a well-known approach to the problem which seeks to iteratively arrive at a solution by allowing each agent to interchange information with at most one neighbor at each iterative step. Crafting a gossiping protocol which accomplishes this is challenging because gossiping is an inherently collaborative process which can lead to deadlocks unless careful precautions are taken to ensure that it does not. Read More

This paper develops a distributed resource allocation game to study countries' pursuit of targets such as self-survival in the networked international environment. The contributions are two. First, the game formalizes countries' power allocation behaviors which fall into the broad category of humans resource allocation behaviors. Read More

A time-invariant, linear, distributed observer is described for estimating the state of an $m>0$ channel, $n$-dimensional continuous-time linear system of the form $ \dot{x} = Ax,\ y_i = C_i x,\ i \in \{1,2,\cdots, m\}$. The state $x$ is simultaneously estimated by $m$ agents assuming each agent $i$ senses $y_i$ and receives the state $z_j$ of each of its neighbors' estimators. Neighbor relations are characterized by a constant directed graph $\mathbb{N}$ whose vertices correspond to agents and whose arcs depict neighbor relations. Read More

On November 12, 2014, the ESA/Rosetta descent module Philae landed on the Abydos site of comet 67P/Churyumov-Gerasimenko. Aboard this module, the Ptolemy mass spectrometer measured a CO/CO2 ratio of 0.07 +/- 0. Read More

A distributed algorithm is described for finding a common fixed point of a family of $m>1$ nonlinear maps $M_i : \mathbb{R}^n \rightarrow \mathbb{R}^n$ assuming that each map is a paracontraction and that such a common fixed point exists. The common fixed point is simultaneously computed by $m$ agents assuming each agent $i$ knows only $M_i$, the current estimates of the fixed point generated by its neighbors, and nothing more. Each agent recursively updates its estimate of the fixed point by utilizing the current estimates generated by each of its neighbors. Read More

In this paper, we survey results regarding the interlace polynomial of a graph, connections to such graph polynomials as the Martin and Tutte polynomials, and generalizations to the realms of isotropic systems and delta-matroids. Read More

The Hera Saturn entry probe mission is proposed as an M--class mission led by ESA with a contribution from NASA. It consists of one atmospheric probe to be sent into the atmosphere of Saturn, and a Carrier-Relay spacecraft. In this concept, the Hera probe is composed of ESA and NASA elements, and the Carrier-Relay Spacecraft is delivered by ESA. Read More

The paper develops a technique for solving a linear equation $Ax=b$ with a square and nonsingular matrix $A$, using a decentralized gradient algorithm. In the language of control theory, there are $n$ agents, each storing at time $t$ an $n$-vector, call it $x_i(t)$, and a graphical structure associating with each agent a vertex of a fixed, undirected and connected but otherwise arbitrary graph $\mathcal G$ with vertex set and edge set $\mathcal V$ and $\mathcal E$ respectively. We provide differential equation update laws for the $x_i$ with the property that each $x_i$ converges to the solution of the linear equation exponentially fast. Read More

A distributed algorithm is described for solving a linear algebraic equation of the form $Ax=b$ assuming the equation has at least one solution. The equation is simultaneously solved by $m$ agents assuming each agent knows only a subset of the rows of the partitioned matrix $(A,b)$, the current estimates of the equation's solution generated by its neighbors, and nothing more. Each agent recursively updates its estimate by utilizing the current estimates generated by each of its neighbors. Read More

By an undirected rigid formation of mobile autonomous agents is meant a formation based on graph rigidity in which each pair of "neighboring" agents is responsible for maintaining a prescribed target distance between them. In a recent paper a systematic method was proposed for devising gradient control laws for asymptotically stabilizing a large class of rigid, undirected formations in two dimensional space assuming all agents are described by kinematic point models. The aim of this paper is to explain what happens to such formations if neighboring agents have slightly different understandings of what the desired distance between them is supposed to be or equivalently if neighboring agents have differing estimates of what the actual distance between them is. Read More

A challenging problem in computational mathematics is to compute roots of a high-degree univariate random polynomial. We combine an efficient multiprecision implementation for solving high-degree random polynomials with two certification methods, namely Smale's $\alpha$-theory and one based on Gerschgorin's theorem, for showing that a given numerical approximation is in the quadratic convergence region of Newton's method of some exact solution. With this combination, we can certifiably count the number of real roots of random polynomials. Read More

Remote sensing observations meet some limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. A remarkable example of the superiority of in situ probe measurements is illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases abundances and the precise measurement of the helium mixing ratio have only been made available through in situ measurements by the Galileo probe. This paper describes the main scientific goals to be addressed by the future in situ exploration of Saturn placing the Galileo probe exploration of Jupiter in a broader context and before the future probe exploration of the more remote ice giants. Read More

Authors: IceCube Collaboration, R. Abbasi, Y. Abdou, T. Abu-Zayyad, J. Adams, J. A. Aguilar, M. Ahlers, K. Andeen, J. Auffenberg, X. Bai, M. Baker, S. W. Barwick, R. Bay, J. L. Bazo Alba, K. Beattie, J. J. Beatty, S. Bechet, J. K. Becker, K. -H. Becker, M. L. Benabderrahmane, S. BenZvi, J. Berdermann, P. Berghaus, D. Berley, E. Bernardini, D. Bertrand, D. Z. Besson, M. Bissok, E. Blaufuss, J. Blumenthal, D. J. Boersma, C. Bohm, D. Bose, S. Böser, O. Botner, J. Braun, S. Buitink, M. Carson, D. Chirkin, B. Christy, J. Clem, F. Clevermann, S. Cohen, C. Colnard, D. F. Cowen, M. V. D'Agostino, M. Danninger, J. C. Davis, C. De Clercq, L. Demirörs, O. Depaepe, F. Descamps, P. Desiati, G. de Vries-Uiterweerd, T. DeYoung, J. C. Díaz-Vélez, M. Dierckxsens, J. Dreyer, J. P. Dumm, M. R. Duvoort, R. Ehrlich, J. Eisch, R. W. Ellsworth, O. Engdegård, S. Euler, P. A. Evenson, O. Fadiran, A. R. Fazely, A. Fedynitch, T. Feusels, K. Filimonov, C. Finley, M. M. Foerster, B. D. Fox, A. Franckowiak, R. Franke, T. K. Gaisser, J. Gallagher, M. Geisler, L. Gerhardt, L. Gladstone, T. Glüsenkamp, A. Goldschmidt, J. A. Goodman, D. Grant, T. Griesel, A. Groß, S. Grullon, M. Gurtner, C. Ha, A. Hallgren, F. Halzen, K. Han, K. Hanson, K. Helbing, P. Herquet, S. Hickford, G. C. Hill, K. D. Hoffman, A. Homeier, K. Hoshina, D. Hubert, W. Huelsnitz, J. -P. Hülß, P. O. Hulth, K. Hultqvist, S. Hussain, A. Ishihara, J. Jacobsen, G. S. Japaridze, H. Johansson, J. M. Joseph, K. -H. Kampert, T. Karg, A. Karle, J. L. Kelley, N. Kemming, P. Kenny, J. Kiryluk, F. Kislat, S. R. Klein, J. -H. Köhne, G. Kohnen, H. Kolanoski, L. Köpke, D. J. Koskinen, M. Kowalski, T. Kowarik, M. Krasberg, T. Krings, G. Kroll, K. Kuehn, T. Kuwabara, M. Labare, S. Lafebre, K. Laihem, H. Landsman, M. J. Larson, R. Lauer, R. Lehmann, J. Lünemann, J. Madsen, P. Majumdar, A. Marotta, R. Maruyama, K. Mase, H. S. Matis, M. Matusik, K. Meagher, M. Merck, P. Mészáros, T. Meures, E. Middell, N. Milke, J. Miller, T. Montaruli, A. R. Morse, S. M. Movit, R. Nahnhauer, J. W. Nam, U. Naumann, P. Nießen, D. R. Nygren, S. Odrowski, A. Olivas, M. Olivo, A. O'Murchadha, M. Ono, S. Panknin, L. Paul, C. Pérez de los Heros, J. Petrovic, A. Piegsa, D. Pieloth, R. Porrata, J. Posselt, P. B. Price, M. Prikockis, G. T. Przybylski, K. Rawlins, P. Redl, E. Resconi, W. Rhode, M. Ribordy, A. Rizzo, J. P. Rodrigues, P. Roth, F. Rothmaier, C. Rott, T. Ruhe, D. Rutledge, B. Ruzybayev, D. Ryckbosch, H. -G. Sander, M. Santander, S. Sarkar, K. Schatto, S. Schlenstedt, T. Schmidt, A. Schukraft, A. Schultes, O. Schulz, M. Schunck, D. Seckel, B. Semburg, S. H. Seo, Y. Sestayo, S. Seunarine, A. Silvestri, K. Singh, A. Slipak, G. M. Spiczak, C. Spiering, M. Stamatikos, B. T. Stanev, G. Stephens, T. Stezelberger, R. G. Stokstad, S. Stoyanov, E. A. Strahler, T. Straszheim, G. W. Sullivan, Q. Swillens, H. Taavola, I. Taboada, A. Tamburro, O. Tarasova, A. Tepe, S. Ter-Antonyan, S. Tilav, P. A. Toale, S. Toscano, D. Tosi, D. Turčan, N. van Eijndhoven, J. Vandenbroucke, A. Van Overloop, J. van Santen, M. Voge, B. Voigt, C. Walck, T. Waldenmaier, M. Wallraff, M. Walter, Ch. Weaver, C. Wendt, S. Westerhoff, N. Whitehorn, K. Wiebe, C. H. Wiebusch, G. Wikström, D. R. Williams, R. Wischnewski, H. Wissing, M. Wolf, K. Woschnagg, C. Xu, X. W. Xu, G. Yodh, S. Yoshida, P. Zarzhitsky

A measurement of the atmospheric muon neutrino energy spectrum from 100 GeV to 400 TeV was performed using a data sample of about 18,000 up-going atmospheric muon neutrino events in IceCube. Boosted decision trees were used for event selection to reject mis-reconstructed atmospheric muons and obtain a sample of up-going muon neutrino events. Background contamination in the final event sample is less than one percent. Read More

We describe the search for a continuous signal of gravitational radiation from a rotating neutron star in the data taken by the ALLEGRO gravitational wave detector in early 1994. Since ALLEGRO is sensitive at frequencies near 1 kHz, only neutron stars with spin periods near 2 ms are potential sources. There are no known sources of this typ e for ALLEGRO, so we directed the search towards both the galactic center and the globular clus ter 47 Tucanae. Read More

This paper introduces and studies the notion of output-input stability, which represents a variant of the minimum-phase property for general smooth nonlinear control systems. The definition of output-input stability does not rely on a particular choice of coordinates in which the system takes a normal form or on the computation of zero dynamics. In the spirit of the ``input-to-state stability'' philosophy, it requires the state and the input of the system to be bounded by a suitable function of the output and derivatives of the output, modulo a decaying term depending on initial conditions. Read More

We discuss the data acquisition and analysis procedures used on the Allegro gravity wave detector, including a full description of the filtering used for bursts of gravity waves. The uncertainties introduced into timing and signal strength estimates due to stationary noise are measured, giving the windows for both quantities in coincidence searches. Read More