36 research outputs found
A Simplex-Based Extension of Fourier-Motzkin for Solving Linear Integer Arithmetic
International audienceThis paper describes a novel decision procedure for quantifier-free linear integer arithmetic. Standard techniques usually relax the initial problem to the rational domain and then proceed either by projection (e.g. Omega-Test) or by branching/cutting methods (branch-and-bound, branch-and-cut, Gomory cuts). Our approach tries to bridge the gap between the two techniques: it interleaves an exhaustive search for a model with bounds inference. These bounds are computed provided an oracle capable of finding constant positive linear combinations of affine forms. We also show how to design an efficient oracle based on the Simplex procedure. Our algorithm is proved sound, complete, and terminating and is implemented in the Alt-Ergo theorem prover. Experimental results are promising and show that our approach is competitive with state-of-the-art SMT solvers
Symmetry preserving regularization with a cutoff
A Lorentz and gauge symmetry preserving regularization method is proposed in
4 dimension based on momentum cutoff. We use the conditions of gauge invariance
or freedom of shift of the loop-momentum to define the evaluation of the terms
carrying Lorentz indices, e.g. proportional to k_{\mu}k_{\nu}. The remaining
scalar integrals are calculated with a four dimensional momentum cutoff. The
finite terms (independent of the cutoff) are unambiguous and agree with the
result of dimensional regularization.Comment: 12 pages, 1 figure, v2 references adde
The Off-diagonal Goldberger-Treiman Relation and Its Discrepancy
We study the off-diagonal Goldberger-Treiman relation (ODGTR) and its
discrepancy (ODGTD) in the N, Delta, pi sector through O(p^2) using heavy
baryon chiral perturbation theory. To this order, the ODGTD and axial vector N
to Delta transition radius are determined solely by low energy constants. Loop
corrections appear at O(p^4). For low-energy constants of natural size, the
ODGTD would represent a ~ 2% correction to the ODGTR. We discuss the
implications of the ODGTR and ODGTD for lattice and quark model calculations of
the transition form factors and for parity-violating electroexcitation of the
Delta.Comment: 11 pages, 1 eps figur
Mechanism of Pion Production in p Scattering at 1 GeV/nucleon
The one-pion and two-pion production in the p(alpha, alpha prime)X reaction
at an energy of E{alpha} = 4.2 GeV has been studied by simultaneous
registration of the scattered alpha particles and the secondary pion or proton.
The obtained results demonstrate that the inelastic alpha-particle scattering
on the proton at the energy of the experiment proceeds either through
excitation and decay of Delta resonance in the projectile or through excitation
in the target proton of the Roper resonance, which decays mainly on a nucleon
and a pion or a nucleon and a sigma meson - system of two pions in the isospin
I = 0, S-wave.Comment: 16 pages, 10 figures. Submitted to Proceedings of the XX
International Baldin Seminar on High - Energy Physics Problems, Dubna,
October 4 - 9, 201
Report on Experiment CE06: Measurements of Nuclear Reactions using Recoil Detection
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Experimental and theoretical evidences for an intermediate -dressed dibaryon in the NN interaction
Numerous theoretical and experimental arguments are presented in favor of the
generation of intermediate -dressed dibaryon in interaction at
intermediate and short distances. We argue that this intermediate dibaryon can
be responsible for the strong intermediate-range attraction and the short-range
repulsion in the interaction, and also for the short-range correlations in
nuclei. The suggested mechanism for the -dressing of the dibaryon is
identical to that which explains the Roper resonance structure, its dominant
decay modes and its extraordinary low mass. A similar transformation mechanism
from the glue to the scalar field was discovered in decays. The new
experimental data on 2-production in the scalar-isoscalar channel produced
in - and -collisions and in particular the very recent data on
correlations in C and C scattering in the GeV region seems
to corroborate the existence of the -dressed dibaryon in two- and three
nucleon interactions.Comment: 14 pages,4 figure
Model Checking Boot Code from AWS Data Centers
This paper describes our experience with symbolic model checking in an industrial setting. We have proved that the initial boot code running in data centers at Amazon Web Services is memory safe, an essential step in establishing the security of any data center. Standard static analysis tools cannot be easily used on boot code without modification owing to issues not commonly found in higher-level code, including memory-mapped device interfaces, byte-level memory access, and linker scripts. This paper describes automated solutions to these issues and their implementation in the C Bounded Model Checker (CBMC). CBMC is now the first source-level static analysis tool to extract the memory layout described in a linker script for use in its analysis
Biabduction (and related problems) in array separation logic
We investigate array separation logic (\mathsf {ASL}), a variant of symbolic-heap separation logic in which the data structures are either pointers or arrays, i.e., contiguous blocks of memory. This logic provides a language for compositional memory safety proofs of array programs. We focus on the biabduction problem for this logic, which has been established as the key to automatic specification inference at the industrial scale. We present an \mathsf {NP} decision procedure for biabduction in \mathsf {ASL}, and we also show that the problem of finding a consistent solution is \mathsf {NP}-hard. Along the way, we study satisfiability and entailment in \mathsf {ASL}, giving decision procedures and complexity bounds for both problems. We show satisfiability to be \mathsf {NP}-complete, and entailment to be decidable with high complexity. The surprising fact that biabduction is simpler than entailment is due to the fact that, as we show, the element of choice over biabduction solutions enables us to dramatically reduce the search space
The as a resonance in the system
We study the system by solving the Faddeev equations, for which
the input two-body -matrices are obtained by solving the Bethe-Salpeter
equation in the coupled channel formalism. The potentials for the ,
sub-systems and their coupled channels are obtained from chiral
Lagrangians, which have been earlier used to study resonances in these systems
successfully. In this work, we find a resonance in the system with a
mass of MeV and with quantum numbers , .
We identify this state with the . This peak is found where the
energies of the sub-system fall in the region of the
resonance. We do not find evidence for the Roper resonance in our study
indicating a more complex structure for this resonance, nor for any state with
total isospin or