37 research outputs found
BĂ€ume fĂŒr das neue Jahrtausend. Die Vorstellung einer genauen Ressourcenverwaltung im Kreislaufprinzip
Lisa CronjĂ€ger untersucht entlang einer aus dem 19. Jahrhundert stammenden forstwissenschaftlichen Taxationskarte von ClaĂ«s Wilhelm GyldĂ©n, auf welche Weise Zukunft als kartografische Projektion entworfen wird. Das Ziel von GyldĂ©n, den Holzertrag eines Waldes prognostisch zu regulieren, wird hierbei ĂŒber diagrammatische und kalkulatorische Berechnungs- und Darstellungsverfahren erst möglich gemacht. Die Imagination einer genauen Planbarkeit von Ressourcennutzung, kartografische Genauigkeit und die UnterdrĂŒckung von (subalternen) Waldnutzungspraktiken bedingen sich in dieser Konstellation gegenseitig
Exact Separation Logic
Over-approximating (OX) program logics, such as separation logic (SL), are
used for verifying properties of heap-manipulating programs: all terminating
behaviour is characterised, but established results and errors need not be
reachable. OX function specifications are thus incompatible with true
bug-finding supported by symbolic execution tools such as Pulse and Pulse-X. In
contrast, under-approximating (UX) program logics, such as incorrectness
separation logic, are used to find true results and bugs: established results
and errors are reachable, but there is no mechanism for understanding if all
terminating behaviour has been characterised.
We introduce exact separation logic (ESL), which provides fully-verified
function specifications compatible with both OX verification and UX true
bug-funding: all terminating behaviour is characterised, and all established
results and errors are reachable. We prove soundness for ESL with mutually
recursive functions, demonstrating, for the first time, function
compositionality for a UX logic. We show that UX program logics require subtle
definitions of internal and external function specifications compared with the
familiar definitions of OX logics. We investigate the expressivity of ESL and,
for the first time, explore the role of abstraction in UX reasoning by
verifying abstract ESL specifications of various data-structure algorithms. In
doing so, we highlight the difference between abstraction (hiding information)
and over-approximation (losing information). Our findings demonstrate that,
expectedly, abstraction cannot be used as freely in UX logics as in OX logics,
but also that it should be feasible to use ESL to provide tractable function
specifications for self-contained, critical code, which would then be used for
both verification and true bug-finding
Exact separation logic: towards bridging the gap between verification and bug-finding
Over-approximating (OX) program logics, such as separation logic (SL), are used for verifying properties of heap-manipulating programs: all terminating behaviour is characterised, but established results and errors need not be reachable. OX function specifications are thus incompatible with true bug-finding supported by symbolic execution tools such as Pulse and Pulse-X. In contrast, under-approximating (UX) program logics, such as incorrectness separation logic, are used to find true results and bugs: established results and errors are reachable, but there is no mechanism for understanding if all terminating behaviour has been characterised. We introduce exact separation logic (ESL), which provides fully-verified function specifications compatible with both OX verification and UX true bug-funding: all terminating behaviour is characterised and all established results and errors are reachable. We prove soundness for ESL with mutually recursive functions, demonstrating, for the first time, function compositionality for a UX logic. We show that UX program logics require subtle definitions of internal and external function specifications compared with the familiar definitions of OX logics. We investigate the expressivity of ESL and, for the first time, explore the role of abstraction in UX reasoning by verifying abstract ESL specifications of various data-structure algorithms. In doing so, we highlight the difference between abstraction (hiding information) and over-approximation (losing information). Our findings demonstrate that abstraction cannot be used as freely in UX logics as in OX logics, but also that it should be feasible to use ESL to provide tractable function specifications for self-contained, critical code, which would then be used for both verification and true bug-finding
A Perturbative Construction of Lattice Chiral Fermions
We perform a renormalization group transformation to construct a lattice
theory of chiral fermions. The field variables of the continuum theory are
averaged over hypercubes to define lattice fields. Integrating out the
continuum variables in perturbation theory we derive a chirally invariant
effective action for the lattice fields. This is consistent with the
Nielsen-Niniomiya theorem because the effective action is nonlocal. We also
construct the axial current on the lattice and we show that the axial anomaly
of the continuum theory is reproduced in the Schwinger model. This shows that
chiral fermions can be regularized on the lattice.Comment: 8 pages, LaTe
BĂ€ume fĂŒr das neue Jahrtausend : die Vorstellung einer genauen Ressourcenverwaltung im Kreislaufprinzip
Lisa CronjĂ€ger untersucht entlang einer aus dem 19. Jahrhundert stammenden forstwissenschaftlichen Taxationskarte von ClaĂ«s Wilhelm GyldĂ©n, auf welche Weise Zukunft als kartografische Projektion entworfen wird. Das Ziel von GyldĂ©n, den Holzertrag eines Waldes prognostisch zu regulieren, wird hierbei ĂŒber diagrammatische und kalkulatorische Berechnungs- und Darstellungsverfahren erst möglich gemacht. Die Imagination einer genauen Planbarkeit von Ressourcennutzung, kartografische Genauigkeit und die UnterdrĂŒckung von (subalternen) Waldnutzungspraktiken bedingen sich in dieser Konstellation gegenseitig
Umtriebszeiten und planetare Grenzen. Bildmuster der maximalen Ausnutzung natĂŒrlicher Ressourcen
RĂ©volutions et limites planĂ©taires. ModĂšles iconographiques de lâexploitation maximale des ressources naturelles
Lâarticle thĂ©matise le pouvoir performatif des modĂšles iconographiques qui illustrent la crise climatique et la gestion des ressources en perspective historique en mobilisant le concept dâ«images opĂ©ratives» propre aux sciences des mĂ©dias. Tout dâabord, lâanalyse porte sur un graphique de 2009 reprĂ©sentant les limites planĂ©taires, et censĂ© donner Ă voir un «safe operating space for humanity» dans le contexte de la crise climatique et environnementale. Dans un deuxiĂšme temps, Ă lâaide dâune sĂ©rie de cartes didactiques des sciences forestiĂšres des XVIIIe et
XIXe siĂšcles, lâarticle met en lumiĂšre la maniĂšre dont les systĂšmes de rotation respectifs dĂ©finissent les limites de lâexploitation maximale des ressources en bois et Ă©tablissent ainsi un mode de contrĂŽle circulaire. Lâarticle questionne cette stratĂ©gie iconographique, qui, bien quâelle mette en scĂšne des limites temporaires de lâexploitation des ressources, prĂ©sente Ă long terme un cycle stable de coupes et de reboisements et finit par amener Ă relativiser la finitude des ressources naturelles