TY - JOUR AB - A rotating organic cation and a dynamically disordered soft inorganic cage are the hallmark features of organic-inorganic lead-halide perovskites. Understanding the interplay between these two subsystems is a challenging problem, but it is this coupling that is widely conjectured to be responsible for the unique behavior of photocarriers in these materials. In this work, we use the fact that the polarizability of the organic cation strongly depends on the ambient electrostatic environment to put the molecule forward as a sensitive probe of the local crystal fields inside the lattice cell. We measure the average polarizability of the C/N–H bond stretching mode by means of infrared spectroscopy, which allows us to deduce the character of the motion of the cation molecule, find the magnitude of the local crystal field, and place an estimate on the strength of the hydrogen bond between the hydrogen and halide atoms. Our results pave the way for understanding electric fields in lead-halide perovskites using infrared bond spectroscopy. AU - Wei, Yujing AU - Volosniev, Artem AU - Lorenc, Dusan AU - Zhumekenov, Ayan A. AU - Bakr, Osman M. AU - Lemeshko, Mikhail AU - Alpichshev, Zhanybek ID - 13251 IS - 27 JF - The Journal of Physical Chemistry Letters KW - General Materials Science KW - Physical and Theoretical Chemistry TI - Bond polarizability as a probe of local crystal fields in hybrid lead-halide perovskites VL - 14 ER - TY - CONF AB - The operator precedence languages (OPLs) represent the largest known subclass of the context-free languages which enjoys all desirable closure and decidability properties. This includes the decidability of language inclusion, which is the ultimate verification problem. Operator precedence grammars, automata, and logics have been investigated and used, for example, to verify programs with arithmetic expressions and exceptions (both of which are deterministic pushdown but lie outside the scope of the visibly pushdown languages). In this paper, we complete the picture and give, for the first time, an algebraic characterization of the class of OPLs in the form of a syntactic congruence that has finitely many equivalence classes exactly for the operator precedence languages. This is a generalization of the celebrated Myhill-Nerode theorem for the regular languages to OPLs. As one of the consequences, we show that universality and language inclusion for nondeterministic operator precedence automata can be solved by an antichain algorithm. Antichain algorithms avoid determinization and complementation through an explicit subset construction, by leveraging a quasi-order on words, which allows the pruning of the search space for counterexample words without sacrificing completeness. Antichain algorithms can be implemented symbolically, and these implementations are today the best-performing algorithms in practice for the inclusion of finite automata. We give a generic construction of the quasi-order needed for antichain algorithms from a finite syntactic congruence. This yields the first antichain algorithm for OPLs, an algorithm that solves the ExpTime-hard language inclusion problem for OPLs in exponential time. AU - Henzinger, Thomas A AU - Kebis, Pavol AU - Mazzocchi, Nicolas Adrien AU - Sarac, Naci E ID - 13292 SN - 9783959772785 T2 - 50th International Colloquium on Automata, Languages, and Programming TI - Regular methods for operator precedence languages VL - 261 ER - TY - JOUR AB - Recent experimental advances have inspired the development of theoretical tools to describe the non-equilibrium dynamics of quantum systems. Among them an exact representation of quantum spin systems in terms of classical stochastic processes has been proposed. Here we provide first steps towards the extension of this stochastic approach to bosonic systems by considering the one-dimensional quantum quartic oscillator. We show how to exactly parameterize the time evolution of this prototypical model via the dynamics of a set of classical variables. We interpret these variables as stochastic processes, which allows us to propose a novel way to numerically simulate the time evolution of the system. We benchmark our findings by considering analytically solvable limits and providing alternative derivations of known results. AU - Tucci, Gennaro AU - De Nicola, Stefano AU - Wald, Sascha AU - Gambassi, Andrea ID - 13277 IS - 2 JF - SciPost Physics Core KW - Statistical and Nonlinear Physics KW - Atomic and Molecular Physics KW - and Optics KW - Nuclear and High Energy Physics KW - Condensed Matter Physics SN - 2666-9366 TI - Stochastic representation of the quantum quartic oscillator VL - 6 ER - TY - JOUR AB - We introduce a generic and accessible implementation of an exact diagonalization method for studying few-fermion models. Our aim is to provide a testbed for the newcomers to the field as well as a stepping stone for trying out novel optimizations and approximations. This userguide consists of a description of the algorithm, and several examples in varying orders of sophistication. In particular, we exemplify our routine using an effective-interaction approach that fixes the low-energy physics. We benchmark this approach against the existing data, and show that it is able to deliver state-of-the-art numerical results at a significantly reduced computational cost. AU - Rammelmüller, Lukas AU - Huber, David AU - Volosniev, Artem ID - 13276 JF - SciPost Physics Codebases SN - 2949-804X TI - A modular implementation of an effective interaction approach for harmonically trapped fermions in 1D ER - TY - GEN AB - We introduce a generic and accessible implementation of an exact diagonalization method for studying few-fermion models. Our aim is to provide a testbed for the newcomers to the field as well as a stepping stone for trying out novel optimizations and approximations. This userguide consists of a description of the algorithm, and several examples in varying orders of sophistication. In particular, we exemplify our routine using an effective-interaction approach that fixes the low-energy physics. We benchmark this approach against the existing data, and show that it is able to deliver state-of-the-art numerical results at a significantly reduced computational cost. AU - Rammelmüller, Lukas AU - Huber, David AU - Volosniev, Artem ID - 13275 TI - Codebase release 1.0 for FermiFCI ER -