19,142 research outputs found
Hard core attraction in hadron scattering and the family of the Ds meson molecule
We study the discovered Ds(2317) at BABAR, CLEO and BELLE, and find that it
belongs to a class of strange multiquarks, which is equivalent to the class of
kaonic molecules bound by hard core attraction. In this class of hadrons a kaon
is trapped by a s-wave meson or baryon. To describe this class of multiquarks
we apply the Resonating Group Method, and extract the hard core
kaon-meson(baryon)interactions. We derive a criterion to classify the
attractive channels. We find that the mesons f0(980), Ds(2457), Bs scalar and
axial, and also the baryons with the quantum numbers of Lambda, Xi_c, Xi_b and
also Omega_cc, Omega_cb and Omega_bb belong to the new hadronic class of the
Ds(2317).Comment: 5 pages, 1 figure, 2 tables, contribution to the X International
Conference on Hadron Spectroscopy, HADRON 2003, August 31 - September 6,
2003, Aschaffenburg, German
The Theta+ (1540) as an overlap of a pion, a kaon and a nucleon
We study the very recently discovered (1540) at SPring-8, at ITEP
and at CLAS-Thomas Jefferson Lab. We apply the same RGM techniques that already
explained with success the repulsive hard core of nucleon-nucleon, kaon-nucleon
exotic scattering, and the attractive hard core present in pion-nucleon and
pion-pion non-exotic scattering. We find that the K-N repulsion excludes the
Theta+ as a K-N s-wave pentaquark. We explore the Theta+ as heptaquark,
equivalent to a N+pi+K borromean boundstate, with positive parity and total
isospin I=0. We find that the kaon-nucleon repulsion is cancelled by the
attraction existing both in the pion-nucleon and pion-kaon channels. Although
we are not yet able to bind the total three body system, we find that the
Theta+ may still be a heptaquark state.Comment: 5 pages, 3 figures, 1 table, contribution to the X International
Conference on Hadron Spectroscopy, HADRON 2003, August 31 - September 6,
2003, Aschaffenburg, German
Effective Lower Bounding Techniques for Pseudo-Boolean Optimization
Linear Pseudo-Boolean Optimization (PBO) is a widely used modeling framework in Electronic Design Automation (EDA). Due to significant advances in Boolean Satisfiability (SAT), new algorithms for PBO have emerged, which are effective on highly constrained instances. However, these algorithms fail to handle effectively the information provided by the cost function of PBO. This paper addresses the integration of lower bound estimation methods with SAT-related techniques in PBO solvers. Moreover, the paper shows that the utilization of lower bound estimates can dramatically improve the overall performance of PBO solvers for most existing benchmarks from EDA. 1
On Computing Minimum Unsatisfiable Cores
Certifying the correctness of a SAT solver is straightforward for satisfiable instances of SAT. Given
Satisfiability-Based Algorithms for Boolean Optimization
This paper proposes new algorithms for the Binate Covering Problem (BCP), a well-known restriction of Boolean Optimization. Binate Covering finds application in many areas of Computer Science and Engineering. In Artificial Intelligence, BCP can be used for computing minimum-size prime implicants of Boolean functions, of interest in Automated Reasoning and Non-Monotonic Reasoning. Moreover, Binate Covering is an essential modeling tool in Electronic Design Automation. The objectives of the paper are to briefly review branch-and-bound algorithms for BCP, to describe how to apply backtrack search pruning techniques from the Boolean Satisfiability (SAT) domain to BCP, and to illustrate how to strengthen those pruning techniques by exploiting the actual formulation of BCP. Experimental results, obtained on representative instances indicate that the proposed techniques provide significant performance gains for a large number of problem instances
Hidden Structure in Unsatisfiable Random 3-SAT: an Empirical Study
Recent advances in propositional satisfiability (SAT) include studying the hidden structure of unsatisfiable formulas, i.e. explaining why a given formula is unsatisfiable. Although theoretical work on the topic has been developed in the past, only recently two empirical successful approaches have been proposed: extracting unsatisfiable cores and identifying strong backdoors. An unsatisfiable core is a subset of clauses that defines a sub-formula that is also unsatisfiable, whereas a strong backdoor defines a subset of variables which assigned with all values allow concluding that the formula is unsatisfiable. The contribution of this paper is two-fold. First, we study the relation between the search complexity of unsatisfiable random 3-SAT formulas and the sizes of unsatisfiable cores and strong backdoors. For this purpose, we use an existing algorithm which uses an approximated approach for calculating these values. Second, we introduce a new algorithm that optimally reduces the size of unsatisfiable cores and strong backdoors, thus giving more accurate results. Experimental results indicate that the search complexity of unsatisfiable random 3-SAT formulas is related with the size of unsatisfiable cores and strong backdoors. 1
- …