@article{2126, abstract = {Let K be an irreducible and reversible Markov kernel on a finite set X. We construct a metric W on the set of probability measures on X and show that with respect to this metric, the law of the continuous time Markov chain evolves as the gradient flow of the entropy. This result is a discrete counterpart of the Wasserstein gradient flow interpretation of the heat flow in Rn by Jordan, Kinderlehrer and Otto (1998). The metric W is similar to, but different from, the L2-Wasserstein metric, and is defined via a discrete variant of the Benamou–Brenier formula. }, author = {Jan Maas}, journal = {Journal of Functional Analysis}, number = {8}, pages = {2250 -- 2292}, publisher = {Academic Press}, title = {{Gradient flows of the entropy for finite Markov chains}}, doi = {10.1016/j.jfa.2011.06.009 }, volume = {261}, year = {2011}, } @unpublished{2138, abstract = {A (diatomic) shape resonance is a metastable state of a pair of colliding atoms quasi-bound by the centrifugal barrier imposed by the angular momentum involved in the collision. The temporary trapping of the atoms' scattering wavefunction corresponds to an enhanced atom pair density at low interatomic separations. This leads to larger overlap of the wavefunctions involved in a molecule formation process such as photoassociation, rendering the process more efficient. However, for an ensemble of atoms, the atom pair density will only be enhanced if the energy of the resonance comes close to the temperature of the atomic ensemble. Herein we explore the possibility of controlling the energy of a shape resonance by shifting it toward the temperature of atoms confined in a trap. The shifts are imparted by the interaction of non-resonant light with the anisotropic polarizability of the atom pair, which affects both the centrifugal barrier and the pair's rotational and vibrational levels. We find that at laser intensities of up to 5×109 W/cm2 the pair density is increased by one order of magnitude for 87Rb atoms at 100μK and by two orders of magnitude for 88Sr atoms at 20μK.}, author = {Ağanoğlu, Ruzin and Mikhail Lemeshko and Friedrich, Břetislav and González-Férez, Rosario and Koch, Christiane P}, booktitle = {Unknown}, publisher = {ArXiv}, title = {{Controlling a diatomic shape resonance with non-resonant light}}, year = {2011}, } @article{2198, abstract = {We show that dressing polar molecules with a far-off-resonant optical field leads to new types of intermolecular potentials, which undergo a crossover from the inverse power to oscillating behavior depending on the intermolecular distance, and whose parameters can be tuned by varying the laser intensity and wavelength. We present analytic expressions for the potential energy surfaces, thereby providing direct access to the parameters of an optical field required to design intermolecular interactions experimentally.}, author = {Mikhail Lemeshko}, journal = {Physical Review A - Atomic, Molecular, and Optical Physics}, number = {5}, publisher = {American Physical Society}, title = {{Shaping interactions between polar molecules with far-off-resonant light}}, doi = {10.1103/PhysRevA.83.051402}, volume = {83}, year = {2011}, } @article{2199, abstract = {By invoking supersymmetry, we found a condition under which the Stark-effect problem for a polar and polarizable molecule subject to nonresonant electric fields becomes exactly solvable for the family of stretched states. The analytic expressions for the wave function and eigenenergy and other expectation values allow one to readily reverse-engineer the problem of finding the values of the interaction parameters required for creating quantum states with preordained characteristics. The method also allows the construction of families of isospectral potentials, realizable with combined fields.}, author = {Mikhail Lemeshko and Mustafa, Mustafa K and Kais, Sabre and Friedrich, Břetislav}, journal = {Physical Review A - Atomic, Molecular, and Optical Physics}, number = {4}, publisher = {American Physical Society}, title = {{Supersymmetric factorization yields exact solutions to the molecular Stark-effect problem for "stretched" states}}, doi = {10.1103/PhysRevA.83.043415}, volume = {83}, year = {2011}, } @article{2200, abstract = {We made use of supersymmetric (SUSY) quantum mechanics to find the condition under which the Stark effect problem for a polar and polarizable closed-shell diatomic molecule subjected to collinear electrostatic and nonresonant radiative fields becomes exactly solvable. The condition Δω = ω2/4(m+1)2 connects values of the dimensionless parameters ω and Δω that characterize the strengths of the permanent and induced dipole interactions of the molecule with the respective fields. The exact solutions are obtained for the \J̃ = m, m; ω, Δω) family of 'stretched' states. The field-free and strong-field limits of the combined-fields problem were found to exhibit supersymmetry and shape invariance, which is indeed the reason why they are analytically solvable. By making use of the analytic form of the \J̃ = m,m; ω, Δω) wavefunctions, we obtained simple formulae for the expectation values of the space-fixed electric dipole moment, the alignment cosine and the angular momentum squared, and derived a 'sum rule' that combines the above expectation values into a formula for the eigenenergy. The analytic expressions for the characteristics of the strongly oriented and aligned states provide direct access to the values of the interaction parameters required for creating such states in the laboratory.}, author = {Mikhail Lemeshko and Mustafa, Mustafa K and Kais, Sabre and Friedrich, Břetislav}, journal = {New Journal of Physics}, publisher = {IOP Publishing Ltd.}, title = {{Supersymmetry identifies molecular Stark states whose eigenproperties can be obtained analytically}}, doi = {10.1088/1367-2630/13/6/063036}, volume = {13}, year = {2011}, } @inproceedings{2320, abstract = {The binding of polarons, or its absence, is an old and subtle topic. After defining the model we state some recent theorems of ours. First, the transition from many-body collapse to the existence of a thermodynamic limit for N polarons occurs precisely at U = 2α, where U is the electronic Coulomb repulsion and α is the polaron coupling constant. Second, if U is large enough, there is no multi-polaron binding of any kind. We also discuss the Pekar-Tomasevich approximation to the ground state energy, which is valid for large α. Finally, we derive exact results, not reported before, about the one-dimensional toy model introduced by E. P. Gross.}, author = {Frank, Rupert L and Lieb, Élliott H and Robert Seiringer and Thomas, Lawrence E}, pages = {21 -- 32}, publisher = {World Scientific Publishing}, title = {{Binding, stability, and non-binding of multi-polaron systems}}, doi = {10.1142/9789814350365_0002}, year = {2011}, } @inproceedings{2321, abstract = {We derive a sharp bound on the location of non-positive eigenvalues of Schrödinger operators on the half-line with complex-valued potentials.}, author = {Frank, Rupert L and Laptev, Ari and Robert Seiringer}, pages = {39 -- 44}, publisher = {Springer}, title = {{ A sharp bound on eigenvalues of Schrödinger operators on the halfline with complex-valued potentials}}, doi = {10.1007/978-3-7643-9994-8_3}, volume = {214}, year = {2011}, } @article{2390, abstract = {We resolve several longstanding problems concerning the stability and the absence of multi-particle binding for N≥2 polarons. Fröhlich's 1937 polaron model describes non-relativistic particles interacting with a scalar quantized field with coupling √α, and with each other by Coulomb repulsion of strength U. We prove the following: (i) While there is a known thermodynamic instability for U<2α, stability of matter does hold for U>2α, that is, the ground state energy per particle has a finite limit as N→∞. (ii) There is no binding of any kind if U exceeds a critical value that depends on α but not on N. The same results are shown to hold for the Pekar-Tomasevich model.}, author = {Frank, Rupert L and Lieb, Élliott H and Robert Seiringer and Thomas, Lawrence E}, journal = {Publications Mathematiques de l Institut des Hautes Etudes Scientifiques}, number = {1}, pages = {39 -- 67}, publisher = {Springer}, title = {{Stability and absence of binding for multi-polaron systems}}, doi = {10.1007/s10240-011-0031-5}, volume = {113}, year = {2011}, } @article{2391, abstract = {The change in energy of an ideal Fermi gas when a local one-body potential is inserted into the system, or when the density is changed locally, are important quantities in condensed matter physics. We show that they can be rigorously bounded from below by a universal constant times the value given by the semiclassical approximation.}, author = {Frank, Rupert L and Lewin, Mathieu and Lieb, Élliott H and Robert Seiringer}, journal = {Physical Review Letters}, number = {15}, publisher = {American Physical Society}, title = {{Energy cost to make a hole in the fermi sea}}, doi = {10.1103/PhysRevLett.106.150402}, volume = {106}, year = {2011}, } @article{2393, abstract = {We investigate the low energy excitation spectrum of a Bose gas with weak, long range repulsive interactions. In particular, we prove that the Bogoliubov spectrum of elementary excitations with linear dispersion relation for small momentum becomes exact in the mean-field limit.}, author = {Robert Seiringer}, journal = {Communications in Mathematical Physics}, number = {2}, pages = {565 -- 578}, publisher = {Springer}, title = {{The excitation spectrum for weakly interacting Bosons}}, doi = {10.1007/s00220-011-1261-6}, volume = {306}, year = {2011}, } @article{6749, abstract = {This article refers to algorithms based on finite difference schemes for computing mean and affine curvature evolutions of digital images, introduced by Alvarez and Morel [L. Alvarez, J.M. Morel, “Formalization and computational aspects of image analysis”, Acta Numerica, pp. 159, 1994]. We discuss consistency, stability and convergence. Our analysis focuses on some possible choices of the parameters, choices that generate multiple variants in the implementations. Meaningful visual examples on how the algorithms actually work are provided.}, author = {Mondelli, Marco and Ciomaga, Adina}, issn = {2105-1232}, journal = {Image Processing On Line}, pages = {127--177}, publisher = {IPOL Image Processing On Line}, title = {{Finite difference schemes for MCM and AMSS}}, doi = {10.5201/ipol.2011.cm_fds}, volume = {1}, year = {2011}, } @article{469, abstract = {Spontaneous release of glutamate is important for maintaining synaptic strength and controlling spike timing in the brain. Mechanisms regulating spontaneous exocytosis remain poorly understood. Extracellular calcium concentration ([Ca2+]o) regulates Ca2+ entry through voltage-activated calcium channels (VACCs) and consequently is a pivotal determinant of action potential-evoked vesicle fusion. Extracellular Ca 2+ also enhances spontaneous release, but via unknown mechanisms. Here we report that external Ca2+ triggers spontaneous glutamate release more weakly than evoked release in mouse neocortical neurons. Blockade of VACCs has no effect on the spontaneous release rate or its dependence on [Ca2+]o. Intracellular [Ca2+] slowly increases in a minority of neurons following increases in [Ca2+]o. Furthermore, the enhancement of spontaneous release by extracellular calcium is insensitive to chelation of intracellular calcium by BAPTA. Activation of the calcium-sensing receptor (CaSR), a G-protein-coupled receptor present in nerve terminals, by several specific agonists increased spontaneous glutamate release. The frequency of spontaneous synaptic transmission was decreased in CaSR mutant neurons. The concentration-effect relationship for extracellular calcium regulation of spontaneous release was well described by a combination of CaSR-dependent and CaSR-independent mechanisms. Overall these results indicate that extracellular Ca2+ does not trigger spontaneous glutamate release by simply increasing calcium influx but stimulates CaSR and thereby promotes resting spontaneous glutamate release. }, author = {Vyleta, Nicholas and Smith, Stephen}, journal = {European Journal of Neuroscience}, number = {12}, pages = {4593 -- 4606}, publisher = {Wiley-Blackwell}, title = {{Spontaneous glutamate release is independent of calcium influx and tonically activated by the calcium-sensing receptor}}, doi = {10.1523/JNEUROSCI.6398-10.2011}, volume = {31}, year = {2011}, } @article{490, abstract = {BioSig is an open source software library for biomedical signal processing. The aim of the BioSig project is to foster research in biomedical signal processing by providing free and open source software tools for many different application areas. Some of the areas where BioSig can be employed are neuroinformatics, brain-computer interfaces, neurophysiology, psychology, cardiovascular systems, and sleep research. Moreover, the analysis of biosignals such as the electroencephalogram (EEG), electrocorticogram (ECoG), electrocardiogram (ECG), electrooculogram (EOG), electromyogram (EMG), or respiration signals is a very relevant element of the BioSig project. Specifically, BioSig provides solutions for data acquisition, artifact processing, quality control, feature extraction, classification, modeling, and data visualization, to name a few. In this paper, we highlight several methods to help students and researchers to work more efficiently with biomedical signals. }, author = {Schlögl, Alois and Vidaurre, Carmen and Sander, Tilmann}, journal = {Computational Intelligence and Neuroscience}, publisher = {Hindawi Publishing Corporation}, title = {{BioSig: The free and open source software library for biomedical signal processing}}, doi = {10.1155/2011/935364}, volume = {2011}, year = {2011}, } @article{518, abstract = {Cancer stem cells or cancer initiating cells are believed to contribute to cancer recurrence after therapy. MicroRNAs (miRNAs) are short RNA molecules with fundamental roles in gene regulation. The role of miRNAs in cancer stem cells is only poorly understood. Here, we report miRNA expression profiles of glioblastoma stem cell-containing CD133 + cell populations. We find that miR-9, miR-9 * (referred to as miR-9/9 *), miR-17 and miR-106b are highly abundant in CD133 + cells. Furthermore, inhibition of miR-9/9 * or miR-17 leads to reduced neurosphere formation and stimulates cell differentiation. Calmodulin-binding transcription activator 1 (CAMTA1) is a putative transcription factor, which induces the expression of the anti-proliferative cardiac hormone natriuretic peptide A (NPPA). We identify CAMTA1 as an miR-9/9 * and miR-17 target. CAMTA1 expression leads to reduced neurosphere formation and tumour growth in nude mice, suggesting that CAMTA1 can function as tumour suppressor. Consistently, CAMTA1 and NPPA expression correlate with patient survival. Our findings could provide a basis for novel strategies of glioblastoma therapy.}, author = {Schraivogel, Daniel and Weinmann, Lasse and Beier, Dagmar and Tabatabai, Ghazaleh and Eichner, Alexander and Zhu, Jia and Anton, Martina and Sixt, Michael K and Weller, Michael and Beier, Christoph and Meister, Gunter}, journal = {EMBO Journal}, number = {20}, pages = {4309 -- 4322}, publisher = {Wiley-Blackwell}, title = {{CAMTA1 is a novel tumour suppressor regulated by miR-9/9 * in glioblastoma stem cells}}, doi = {10.1038/emboj.2011.301}, volume = {30}, year = {2011}, } @article{531, abstract = {Software transactional memories (STM) are described in the literature with assumptions of sequentially consistent program execution and atomicity of high level operations like read, write, and abort. However, in a realistic setting, processors use relaxed memory models to optimize hardware performance. Moreover, the atomicity of operations depends on the underlying hardware. This paper presents the first approach to verify STMs under relaxed memory models with atomicity of 32 bit loads and stores, and read-modify-write operations. We describe RML, a simple language for expressing concurrent programs. We develop a semantics of RML parametrized by a relaxed memory model. We then present our tool, FOIL, which takes as input the RML description of an STM algorithm restricted to two threads and two variables, and the description of a memory model, and automatically determines the locations of fences, which if inserted, ensure the correctness of the restricted STM algorithm under the given memory model. We use FOIL to verify DSTM, TL2, and McRT STM under the memory models of sequential consistency, total store order, partial store order, and relaxed memory order for two threads and two variables. Finally, we extend the verification results for DSTM and TL2 to an arbitrary number of threads and variables by manually proving that the structural properties of STMs are satisfied at the hardware level of atomicity under the considered relaxed memory models.}, author = {Guerraoui, Rachid and Henzinger, Thomas A and Singh, Vasu}, journal = {Formal Methods in System Design}, number = {3}, pages = {297 -- 331}, publisher = {Springer}, title = {{Verification of STM on relaxed memory models}}, doi = {10.1007/s10703-011-0131-3}, volume = {39}, year = {2011}, } @misc{5379, abstract = {Computing the winning set for Büchi objectives in alternating games on graphs is a central problem in computer aided verification with a large number of applications. The long standing best known upper bound for solving the problem is ̃O(n·m), where n is the number of vertices and m is the number of edges in the graph. We are the first to break the ̃O(n·m) boundary by presenting a new technique that reduces the running time to O(n2). This bound also leads to O(n2) time algorithms for computing the set of almost-sure winning vertices for Büchi objectives (1) in alternating games with probabilistic transitions (improving an earlier bound of O(n·m)), (2) in concurrent graph games with constant actions (improving an earlier bound of O(n3)), and (3) in Markov decision processes (improving for m > n4/3 an earlier bound of O(min(m1.5, m·n2/3)). We also show that the same technique can be used to compute the maximal end-component decomposition of a graph in time O(n2), which is an improvement over earlier bounds for m > n4/3. Finally, we show how to maintain the winning set for Büchi objectives in alternating games under a sequence of edge insertions or a sequence of edge deletions in O(n) amortized time per operation. This is the first dynamic algorithm for this problem.}, author = {Chatterjee, Krishnendu and Henzinger, Monika H}, issn = {2664-1690}, pages = {20}, publisher = {IST Austria}, title = {{An O(n2) time algorithm for alternating Büchi games}}, doi = {10.15479/AT:IST-2011-0009}, year = {2011}, } @misc{5380, abstract = {We consider 2-player games played on a finite state space for an infinite number of rounds. The games are concurrent: in each round, the two players (player 1 and player 2) choose their moves independently and simultaneously; the current state and the two moves determine the successor state. We study concurrent games with ω-regular winning conditions specified as parity objectives. We consider the qualitative analysis problems: the computation of the almost-sure and limit-sure winning set of states, where player 1 can ensure to win with probability 1 and with probability arbitrarily close to 1, respectively. In general the almost-sure and limit-sure winning strategies require both infinite-memory as well as infinite-precision (to describe probabilities). We study the bounded-rationality problem for qualitative analysis of concurrent parity games, where the strategy set for player 1 is restricted to bounded-resource strategies. In terms of precision, strategies can be deterministic, uniform, finite-precision or infinite-precision; and in terms of memory, strategies can be memoryless, finite-memory or infinite-memory. We present a precise and complete characterization of the qualitative winning sets for all combinations of classes of strategies. In particular, we show that uniform memoryless strategies are as powerful as finite-precision infinite-memory strategies, and infinite-precision memoryless strategies are as powerful as infinite-precision finite-memory strategies. We show that the winning sets can be computed in O(n2d+3) time, where n is the size of the game structure and 2d is the number of priorities (or colors), and our algorithms are symbolic. The membership problem of whether a state belongs to a winning set can be decided in NP ∩ coNP. While this complexity is the same as for the simpler class of turn-based parity games, where in each state only one of the two players has a choice of moves, our algorithms,that are obtained by characterization of the winning sets as μ-calculus formulas, are considerably more involved than those for turn-based games.}, author = {Chatterjee, Krishnendu}, issn = {2664-1690}, pages = {53}, publisher = {IST Austria}, title = {{Bounded rationality in concurrent parity games}}, doi = {10.15479/AT:IST-2011-0008}, year = {2011}, } @misc{5381, abstract = {In two-player finite-state stochastic games of partial obser- vation on graphs, in every state of the graph, the players simultaneously choose an action, and their joint actions determine a probability distri- bution over the successor states. The game is played for infinitely many rounds and thus the players construct an infinite path in the graph. We consider reachability objectives where the first player tries to ensure a target state to be visited almost-surely (i.e., with probability 1) or pos- itively (i.e., with positive probability), no matter the strategy of the second player. We classify such games according to the information and to the power of randomization available to the players. On the basis of information, the game can be one-sided with either (a) player 1, or (b) player 2 having partial observation (and the other player has perfect observation), or two- sided with (c) both players having partial observation. On the basis of randomization, (a) the players may not be allowed to use randomization (pure strategies), or (b) they may choose a probability distribution over actions but the actual random choice is external and not visible to the player (actions invisible), or (c) they may use full randomization. Our main results for pure strategies are as follows: (1) For one-sided games with player 2 perfect observation we show that (in contrast to full randomized strategies) belief-based (subset-construction based) strate- gies are not sufficient, and present an exponential upper bound on mem- ory both for almost-sure and positive winning strategies; we show that the problem of deciding the existence of almost-sure and positive winning strategies for player 1 is EXPTIME-complete and present symbolic algo- rithms that avoid the explicit exponential construction. (2) For one-sided games with player 1 perfect observation we show that non-elementary memory is both necessary and sufficient for both almost-sure and posi- tive winning strategies. (3) We show that for the general (two-sided) case finite-memory strategies are sufficient for both positive and almost-sure winning, and at least non-elementary memory is required. We establish the equivalence of the almost-sure winning problems for pure strategies and for randomized strategies with actions invisible. Our equivalence re- sult exhibit serious flaws in previous results in the literature: we show a non-elementary memory lower bound for almost-sure winning whereas an exponential upper bound was previously claimed.}, author = {Chatterjee, Krishnendu and Doyen, Laurent}, issn = {2664-1690}, pages = {43}, publisher = {IST Austria}, title = {{Partial-observation stochastic games: How to win when belief fails}}, doi = {10.15479/AT:IST-2011-0007}, year = {2011}, } @misc{5382, abstract = {We consider two-player stochastic games played on a finite state space for an infinite num- ber of rounds. The games are concurrent: in each round, the two players (player 1 and player 2) choose their moves independently and simultaneously; the current state and the two moves determine a probability distribution over the successor states. We also consider the important special case of turn-based stochastic games where players make moves in turns, rather than concurrently. We study concurrent games with ω-regular winning conditions specified as parity objectives. The value for player 1 for a parity objective is the maximal probability with which the player can guarantee the satisfaction of the objective against all strategies of the opponent. We study the problem of continuity and robustness of the value function in concurrent and turn-based stochastic parity games with respect to imprecision in the transition probabilities. We present quantitative bounds on the difference of the value function (in terms of the imprecision of the transition probabilities) and show the value continuity for structurally equivalent concurrent games (two games are structurally equivalent if the support of the transition func- tion is same and the probabilities differ). We also show robustness of optimal strategies for structurally equivalent turn-based stochastic parity games. Finally we show that the value continuity property breaks without the structurally equivalent assumption (even for Markov chains) and show that our quantitative bound is asymptotically optimal. Hence our results are tight (the assumption is both necessary and sufficient) and optimal (our quantitative bound is asymptotically optimal).}, author = {Chatterjee, Krishnendu}, issn = {2664-1690}, pages = {18}, publisher = {IST Austria}, title = {{Robustness of structurally equivalent concurrent parity games}}, doi = {10.15479/AT:IST-2011-0006}, year = {2011}, } @misc{5383, abstract = {We present a new decidable logic called TREX for expressing constraints about imperative tree data structures. In particular, TREX supports a transitive closure operator that can express reachability constraints, which often appear in data structure invariants. We show that our logic is closed under weakest precondition computation, which enables its use for automated software verification. We further show that satisfiability of formulas in TREX is decidable in NP. The low complexity makes it an attractive alternative to more expensive logics such as monadic second-order logic (MSOL) over trees, which have been traditionally used for reasoning about tree data structures.}, author = {Wies, Thomas and Muñiz, Marco and Kuncak, Viktor}, issn = {2664-1690}, pages = {25}, publisher = {IST Austria}, title = {{On an efficient decision procedure for imperative tree data structures}}, doi = {10.15479/AT:IST-2011-0005}, year = {2011}, }