From doubled Chern–Simons–Maxwell lattice gauge theory to extensions of the toric code

We regularize compact and non-compact Abelian Chern–Simons–Maxwell theories on a spatial lattice using the Hamiltonian formulation. We consider a doubled theory with gauge fields living on a lattice and its dual lattice. The Hilbert space of the theory is a product of local Hilbert spaces, each associated with a link and the corresponding dual link. The two electric field operators associated with the link-pair do not commute. In the non-compact case with gauge group R, each local Hilbert space is analogous to the one of a charged “particle” moving in the link-pair group space R2 in a constant “magnetic” background field. In the compact case, the link-pair group space is a torus U(1)2 threaded by k units of quantized “magnetic” flux, with k being the level of the Chern–Simons theory. The holonomies of the torus U(1)2 give rise to two self-adjoint extension parameters, which form two non-dynamical background lattice gauge fields that explicitly break the manifest gauge symmetry from U(1) to Z(k). The local Hilbert space of a link-pair then decomposes into representations of a magnetic translation group. In the pure Chern–Simons limit of a large “photon” mass, this results in a Z(k)-symmetric variant of Kitaev’s toric code, self-adjointly extended by the two non-dynamical background lattice gauge fields. Electric charges on the original lattice and on the dual lattice obey mutually anyonic statistics with the statistics angle . Non-Abelian U(k) Berry gauge fields that arise from the self-adjoint extension parameters may be interesting in the context of quantum information processing.

Chronostratigraphic framework at sites GeoB14403 and GeoB14414 from the Gela Basin, Sicily Channel

A multi-proxy chronological framework along with sequence-stratigraphic interpretations unveils composite Milankovitch cyclicity in the sedimentary records of the Last GlacialeInterglacial cycle at NE Gela Basin on the Sicilian continental margin. Chronostratigraphic data (including foraminifera-based eco-biostratigraphy and d18O records, tephrochronological markers and 14C AMS radiometric datings) was derived from the shallow-shelf drill sites GeoB14403 (54.6 m recovery) and GeoB14414 (27.5 m), collected with both gravity and drilled MeBo cores in 193 m and 146 m water depth, respectively. The recovered intervals record Marine Isotope Stages and Substages (MIS) from MIS 5 to MIS 1, thus comprising major stratigraphic parts of the progradational deposits that form the last 100-ka depositional sequence. Calibration of shelf sedimentary units with borehole stratigraphies indicates the impact of higher-frequency (20-ka) sea level cycles punctuating this 100-ka cycle. This becomes most evident in the alternation of thick interstadial highstand (HST) wedges and thinner glacial forced-regression (FSST) units mirroring seaward shifts in coastal progradation. Albeit their relatively short-lived depositional phase, these subordinate HST units form the bulk of the 100-ka depositional sequence. Two mechanisms are proposed that likely account for enhanced sediment accumulation ratios (SAR) of up to 200 cm/ka during these intervals: (1) intensified activity of deep and intermediate Levantine Intermediate Water (LIW) associated to the drowning of Mediterranean shelves, and (2) amplified sediment flux along the flooded shelf in response to hyperpycnal plumes that generate through extreme precipitation events during overall arid conditions. Equally, the latter mechanism is thought to be at the origin of undulated features resolved in the acoustic records of MIS 5 Interstadials, which bear a striking resemblance to modern equivalents forming on late-Holocene prodeltas of other Mediterranean shallow-shelf settings.

Desterritorialización y heterogeneidad : La traducción literal en la narrativa de Sandra Cisneros

Esta tesis indaga acerca de algunos de los aspectos lingüísticos y discursivos presentes en la construcción de la narrativa de la autora chicana Sandra Cisneros (1954-). En contraposición a la literatura canónica, la literatura chicana se define como escritura de minorías. Según G. Deleuze y F. Guattari (1975), una literatura de minorías se caracteriza por la desterritorialización de una lengua mayoritaria a través de su uso en esa literatura, la articulación de loindividual en lo inmediato político y el dispositivo colectivo de enunciación. La obra de S. Cisneros, que se desarrolla principalmente a partir del inglés, pone de manifiesto el contacto entre el español y el inglés de un modo particular. En este trabajo, se analiza el fenómeno del contacto de lenguas vinculado a la traducción literal, cuya presencia se vuelve un rasgo distintivo del estilo de la autora y una estrategia clave para la desterritorialización del lenguaje. En este sentido, la hipótesis central de nuestra investigación indica que bajo la apariencia de una única lengua, el inglés (L1), hay otra lengua, el español (L2), que se manifiesta en la utilización de alguno de sus niveles (léxico-semántico, pragmático, morfosintáctico o gráfico), lo cual contribuye a la desterritorialización de L1 y constituye un caso especial de alternancia de lenguas. Esta hipótesis ha guiado la clasificación del corpus de esta investigación constituido por frases y estructuras que registran cierta fijación,pertenecientes a la colección de relatos Woman Hollering Creek and Other Stories (1991). El interés en estas formas reside en que si bien aparecen expresadas en inglés, remiten al español como marco discursivo, acentuando el carácter heterogéneo constitutivo de toda palabra. Dado que la traducción literal no integra los modelos sociolingüísticos revisados (S. Poplack: 1982; C. Myers-Scotton: 1993a y 1993b) y considerando que el contacto de lenguastambién se manifiesta a través de esta operación de traducción, que conforma un punto de heterogeneidad fuerte, fue necesario buscar una teoría lingüísticaque pudiera explicar la complejidad el discurso de Cisneros. Así, la teoría de las heterogeneidades enunciativas (J. Authier-Revuz: 1984, 1995) se presenta como un marco más amplio para el estudio de las marcas de heterogeneidad y desterritorialización en el seno de la narrativa de S. Cisneros. Esta perspectivateórica, que da cuenta de los procesos que se ponen en marcha en la constitución del discurso y atiende, entre otras, la función de las marcas gráficas presentes en el texto escrito, propone un marco más amplio para abordar nuestro objeto. Son dos los objetivos principales de esta investigación: describir la operación de desterritorialización en el interior de este discurso y establecer relaciones entre algunos de los modelos que abordan el estudio de la alternancia de lenguas (S. Poplack: 1982; C. Myers-Scotton: 1993a y 1993b) y la teoría de las heterogeneidades enunciativas propuesta por J. Authier-Revuz (1984, 1995).

Desterritorialización y heterogeneidad : La traducción literal en la narrativa de Sandra Cisneros

Esta tesis indaga acerca de algunos de los aspectos lingüísticos y discursivos presentes en la construcción de la narrativa de la autora chicana Sandra Cisneros (1954-). En contraposición a la literatura canónica, la literatura chicana se define como escritura de minorías. Según G. Deleuze y F. Guattari (1975), una literatura de minorías se caracteriza por la desterritorialización de una lengua mayoritaria a través de su uso en esa literatura, la articulación de loindividual en lo inmediato político y el dispositivo colectivo de enunciación. La obra de S. Cisneros, que se desarrolla principalmente a partir del inglés, pone de manifiesto el contacto entre el español y el inglés de un modo particular. En este trabajo, se analiza el fenómeno del contacto de lenguas vinculado a la traducción literal, cuya presencia se vuelve un rasgo distintivo del estilo de la autora y una estrategia clave para la desterritorialización del lenguaje. En este sentido, la hipótesis central de nuestra investigación indica que bajo la apariencia de una única lengua, el inglés (L1), hay otra lengua, el español (L2), que se manifiesta en la utilización de alguno de sus niveles (léxico-semántico, pragmático, morfosintáctico o gráfico), lo cual contribuye a la desterritorialización de L1 y constituye un caso especial de alternancia de lenguas. Esta hipótesis ha guiado la clasificación del corpus de esta investigación constituido por frases y estructuras que registran cierta fijación,pertenecientes a la colección de relatos Woman Hollering Creek and Other Stories (1991). El interés en estas formas reside en que si bien aparecen expresadas en inglés, remiten al español como marco discursivo, acentuando el carácter heterogéneo constitutivo de toda palabra. Dado que la traducción literal no integra los modelos sociolingüísticos revisados (S. Poplack: 1982; C. Myers-Scotton: 1993a y 1993b) y considerando que el contacto de lenguastambién se manifiesta a través de esta operación de traducción, que conforma un punto de heterogeneidad fuerte, fue necesario buscar una teoría lingüísticaque pudiera explicar la complejidad el discurso de Cisneros. Así, la teoría de las heterogeneidades enunciativas (J. Authier-Revuz: 1984, 1995) se presenta como un marco más amplio para el estudio de las marcas de heterogeneidad y desterritorialización en el seno de la narrativa de S. Cisneros. Esta perspectivateórica, que da cuenta de los procesos que se ponen en marcha en la constitución del discurso y atiende, entre otras, la función de las marcas gráficas presentes en el texto escrito, propone un marco más amplio para abordar nuestro objeto. Son dos los objetivos principales de esta investigación: describir la operación de desterritorialización en el interior de este discurso y establecer relaciones entre algunos de los modelos que abordan el estudio de la alternancia de lenguas (S. Poplack: 1982; C. Myers-Scotton: 1993a y 1993b) y la teoría de las heterogeneidades enunciativas propuesta por J. Authier-Revuz (1984, 1995).

Desterritorialización y heterogeneidad : La traducción literal en la narrativa de Sandra Cisneros

Esta tesis indaga acerca de algunos de los aspectos lingüísticos y discursivos presentes en la construcción de la narrativa de la autora chicana Sandra Cisneros (1954-). En contraposición a la literatura canónica, la literatura chicana se define como escritura de minorías. Según G. Deleuze y F. Guattari (1975), una literatura de minorías se caracteriza por la desterritorialización de una lengua mayoritaria a través de su uso en esa literatura, la articulación de loindividual en lo inmediato político y el dispositivo colectivo de enunciación. La obra de S. Cisneros, que se desarrolla principalmente a partir del inglés, pone de manifiesto el contacto entre el español y el inglés de un modo particular. En este trabajo, se analiza el fenómeno del contacto de lenguas vinculado a la traducción literal, cuya presencia se vuelve un rasgo distintivo del estilo de la autora y una estrategia clave para la desterritorialización del lenguaje. En este sentido, la hipótesis central de nuestra investigación indica que bajo la apariencia de una única lengua, el inglés (L1), hay otra lengua, el español (L2), que se manifiesta en la utilización de alguno de sus niveles (léxico-semántico, pragmático, morfosintáctico o gráfico), lo cual contribuye a la desterritorialización de L1 y constituye un caso especial de alternancia de lenguas. Esta hipótesis ha guiado la clasificación del corpus de esta investigación constituido por frases y estructuras que registran cierta fijación,pertenecientes a la colección de relatos Woman Hollering Creek and Other Stories (1991). El interés en estas formas reside en que si bien aparecen expresadas en inglés, remiten al español como marco discursivo, acentuando el carácter heterogéneo constitutivo de toda palabra. Dado que la traducción literal no integra los modelos sociolingüísticos revisados (S. Poplack: 1982; C. Myers-Scotton: 1993a y 1993b) y considerando que el contacto de lenguastambién se manifiesta a través de esta operación de traducción, que conforma un punto de heterogeneidad fuerte, fue necesario buscar una teoría lingüísticaque pudiera explicar la complejidad el discurso de Cisneros. Así, la teoría de las heterogeneidades enunciativas (J. Authier-Revuz: 1984, 1995) se presenta como un marco más amplio para el estudio de las marcas de heterogeneidad y desterritorialización en el seno de la narrativa de S. Cisneros. Esta perspectivateórica, que da cuenta de los procesos que se ponen en marcha en la constitución del discurso y atiende, entre otras, la función de las marcas gráficas presentes en el texto escrito, propone un marco más amplio para abordar nuestro objeto. Son dos los objetivos principales de esta investigación: describir la operación de desterritorialización en el interior de este discurso y establecer relaciones entre algunos de los modelos que abordan el estudio de la alternancia de lenguas (S. Poplack: 1982; C. Myers-Scotton: 1993a y 1993b) y la teoría de las heterogeneidades enunciativas propuesta por J. Authier-Revuz (1984, 1995).

Modular extensions for modular (Logic) languages

We address the problem of developing mechanisms for easily implementing modular extensions to modular (logic) languages. By(language) extensions we refer to different groups of syntactic definitions and translation rules that extend a language. Our use of the concept of modularity in this context is twofold. We would like these extensions to be modular, in the sense above, i.e., we should be able to develop different extensions mostly separately. At the same time, the sources and targets for the extensions are modular languages, i.e., such extensions may take as input sepárate pieces of code and also produce sepárate pieces of code. Dealing with this double requirement involves interesting challenges to ensure that modularity is not broken: first, combinations of extensions (as if they were a single extensión) must be given a precise meaning. Also, the sepárate translation of múltiple sources (as if they were a single source) must be feasible. We present a detailed description of a code expansion-based framework that proposes novel solutions for these problems. We argüe that the approach, while implemented for Ciao, can be adapted for other Prolog-based systems and languages.

Integrating software testing and run-time checking in an assertion verification framework

We have designed and implemented a framework that unifies unit testing and run-time verification (as well as static verification and static debugging). A key contribution of our approach is that a unified assertion language is used for all of these tasks. We first propose methods for compiling runtime checks for (parts of) assertions which cannot be verified at compile-time via program transformation. This transformation allows checking preconditions and postconditions, including conditional postconditions, properties at arbitrary program points, and certain computational properties. The implemented transformation includes several optimizations to reduce run-time overhead. We also propose a minimal addition to the assertion language which allows defining unit tests to be run in order to detect possible violations of the (partial) specifications expressed by the assertions. This language can express for example the input data for performing the unit tests or the number of times that the unit tests should be repeated. We have implemented the framework within the Ciao/CiaoPP system and effectively applied it to the verification of ISO-prolog compliance and to the detection of different types of bugs in the Ciao system source code. Several experimental results are presented that ¡Ilústrate different trade-offs among program size, running time, or levéis of verbosity of the messages shown to the user.

Reduced certificates for abstraction-carrying code

Abstraction-Carrying Code (ACC) has recently been proposed as a framework for mobile code safety in which the code supplier provides a program together with an abstraction whose validity entails compliance with a predefined safety policy. The abstraction plays thus the role of safety certifícate and its generation is carried out automatically by a fixed-point analyzer. The advantage of providing a (fixedpoint) abstraction to the code consumer is that its validity is checked in a single pass of an abstract interpretation-based checker. A main challenge is to reduce the size of certificates as much as possible while at the same time not increasing checking time. We introduce the notion of reduced certifícate which characterizes the subset of the abstraction which a checker needs in order to validate (and re-construct) the full certifícate in a single pass. Based on this notion, we instrument a generic analysis algorithm with the necessary extensions in order to identify the information relevant to the checker. We also provide a correct checking algorithm together with sufficient conditions for ensuring its completeness. The experimental results within the CiaoPP system show that our proposal is able to greatly reduce the size of certificates in practice.

Experiments in abstract interpretation-based code certification for pervasive systems

Proof carrying code (PCC) is a general is originally a roof in ñrst-order logic of certain vermethodology for certifying that the execution of an un- ification onditions and the checking process involves trusted mobile code is safe. The baste idea is that the ensuring that the certifícate is indeed a valid ñrst-order code supplier attaches a certifícate to the mobile code proof. which the consumer checks in order to ensure that the The main practical difñculty of PCC techniques is in code is indeed safe. The potential benefit is that the generating safety certiñeates which at the same time: i) consumer's task is reduced from the level of proving to allow expressing interesting safety properties, ii) can be the level of checking. Recently, the abstract interpre- generated automatically and, iii) are easy and efficient tation techniques developed, in logic programming have to check. In [1], the abstract interpretation techniques been proposed as a basis for PCC. This extended ab- [5] developed in logic programming1 are proposed as stract reports on experiments which illustrate several is- a basis for PCC. They offer a number of advantages sues involved in abstract interpretation-based certifica- for dealing with the aforementioned issues. In particution. First, we describe the implementation of our sys- lar, the xpressiveness of existing abstract domains will tem in the context of CiaoPP: the preprocessor of the be implicitly available in abstract interpretation-based Ciao multi-paradigm programming system. Then, by code certification to deñne a wide range of safety propermeans of some experiments, we show how code certifi- ties. Furthermore, the approach inherits the automation catión is aided in the implementation of the framework. and inference power of the abstract interpretation en- Finally, we discuss the application of our method within gines used in (Constraint) Logic Programming, (C)LP. the área, of pervasive systems

On abstraction-carrying code and certificate-size reduction

Abstraction-Carrying Code (ACC) is a framework for mobile code safety in which the code supplier provides a program together with an abstraction (or abstract model of the program) whose validity entails compliance with a predefined safety policy. The abstraction plays thus the role of safety certificate and its generation is carried out automatically by a fixed-point analyzer. The advantage of providing a (fixed-point) abstraction to the code consumer is that its validity is checked in a single pass (i.e., one iteration) of an abstract interpretation-based checker. A main challenge to make ACC useful in practice is to reduce the size of certificates as much as possible, while at the same time not increasing checking time. Intuitively, we only include in the certificate the information which the checker is unable to reproduce without iterating. We introduce the notion of reduced certifícate which characterizes the subset of the abstraction which a checker needs in order to validate (and re-construct) the full certificate in a single pass. Based on this notion, we show how to instrument a generic analysis algorithm with the necessary extensions in order to identify the information relevant to the checker.

Generation of reduced certificates in abstraction-carrying code

Abstraction-Carrying Code (ACC) has recently been proposed as a framework for mobile code safety in which the code supplier provides a program together with an abstraction whose validity entails compliance with a predefined safety policy. The abstraction plays thus the role of safety certifícate and its generation is carried out automatically by a fixed-point analyzer. The advantage of providing a (fixedpoint) abstraction to the code consumer is that its validity is checked in a single pass of an abstract interpretation-based checker. A main challenge is to reduce the size of certificates as much as possible while at the same time not increasing checking time. In this paper, we first introduce the notion of reduced certifícate which characterizes the subset of the abstraction which a checker needs in order to validate (and re-construct) the full certifícate in a single pass. Based on this notion, we then instrument a generic analysis algorithm with the necessary extensions in order to identify the information relevant to the checker.

Abstract interpretation-based code certification for pervasive systems: Preliminary experiments

Proof carrying code is a general methodology for certifying that the execution of an untrusted mobile code is safe, according to a predefined safety policy. The basic idea is that the code supplier attaches a certifícate (or proof) to the mobile code which, then, the consumer checks in order to ensure that the code is indeed safe. The potential benefit is that the consumer's task is reduced from the level of proving to the level of checking, a much simpler task. Recently, the abstract interpretation techniques developed in logic programming have been proposed as a basis for proof carrying code [1]. To this end, the certifícate is generated from an abstract interpretation-based proof of safety. Intuitively, the verification condition is extracted from a set of assertions guaranteeing safety and the answer table generated during the analysis. Given this information, it is relatively simple and fast to verify that the code does meet this proof and so its execution is safe. This extended abstract reports on experiments which illustrate several issues involved in abstract interpretation-based code certification. First, we describe the implementation of our system in the context of CiaoPP: the preprocessor of the Ciao multi-paradigm (constraint) logic programming system. Then, by means of some experiments, we show how code certification is aided in the implementation of the framework. Finally, we discuss the application of our method within the área of pervasive systems which may lack the necessary computing resources to verify safety on their own. We herein illustrate the relevance of the information inferred by existing cost analysis to control resource usage in this context. Moreover, since the (rather complex) analysis phase is replaced by a simpler, efficient checking process at the code consumer side, we believe that our abstract interpretation-based approach to proof-carrying code becomes practically applicable to this kind of systems.

An abstract interpretation-based approach to mobile code safety

Recent approaches to mobile code safety, like proof- arrying code, involve associating safety information to programs. The code supplier provides a program and also includes with it a certifícate (or proof) whose validity entails compliance with a predefined safety policy. The intended benefit is that the program consumer can locally validate the certifícate w.r.t. the "untrusted" program by means of a certifícate checker—a process which should be much simpler, eflicient, and automatic than generating the original proof. We herein introduce a novel approach to mobile code safety which follows a similar scheme, but which is based throughout on the use of abstract interpretation techniques. In our framework the safety policy is specified by using an expressive assertion language defined over abstract domains. We identify a particular slice of the abstract interpretation-based static analysis results which is especially useful as a certifícate. We propose an algorithm for checking the validity of the certifícate on the consumer side which is itself in fact a very simplified and eflicient specialized abstract-interpreter. Our ideas are illustrated through an example implemented in the CiaoPP system. Though further experimentation is still required, we believe the proposed approach is of interest for bringing the automation and expressiveness which is inherent in the abstract interpretation techniques to the área of mobile code safety.

Towards modular extensions for a modular language

Modularity allows the construction of complex designs from simpler, independent units that most of the time can be developed separately. In this paper we are concerned with developing mechanisms for easily implementing modular extensions to modular (logic) languages. By (language) extensions we refer to different groups of syntactic definitions and translation rules that extend a language. Our application of the concept of modularity in this context is twofold. We would like these extensions to be modular, in the above sense, i.e., we should be able to develop different extensions mostly separately. At the same time, the sources and targets for the extensions are modular languages, i.e., such extensions may take as input separate pieces of code and also produce separate pieces of code. Dealing with this double requirement involves interesting challenges to ensure that modularity is not broken: first, combinations of extensions (as if they were a single extension) must be given a precise meaning. Also, the separate translation of multiple sources (as if they were a single source) must be feasible. We present a detailed description of a code expansion-based framework that proposes novel solutions for these problems. We argue that the approach, while implemented for Ciao, can be adapted for other languages and Prolog-based systems.

Reduced certificates for abstraction-carrying code

Abstraction-Carrying Code (ACC) has recently been proposed as a framework for mobile code safety in which the code supplier provides a program together with an abstraction (or abstract model of the program) whose validity entails compliance with a predefined safety policy. The abstraction plays thus the role of safety certifícate and its generation is carried out automatically by a fixed-point analyzer. The advantage of providing a (fixed-point) abstraction to the code consumer is that its validity is checked in a single pass (i.e., one iteration) of an abstract interpretation-based checker. A main challenge to make ACC useful in practice is to reduce the size of certificates as much as possible while at the same time not increasing checking time. The intuitive idea is to only include in the certifícate information that the checker is unable to reproduce without iterating. We introduce the notion of reduced certifícate which characterizes the subset of the abstraction which a checker needs in order to validate (and re-construct) the full certifícate in a single pass. Based on this notion, we instrument a generic analysis algorithm with the necessary extensions in order to identify information which can be reconstructed by the single-pass checker. Finally, we study what the effects of reduced certificates are on the correctness and completeness of the checking process. We provide a correct checking algorithm together with sufficient conditions for ensuring its completeness. Our ideas are illustrated through a running example, implemented in the context of constraint logic programs, which shows that our approach improves state-of-the-art techniques for reducing the size of certificates.