66 research outputs found
Infinite subgame perfect equilibrium in the Hausdorff difference hierarchy
Subgame perfect equilibria are specific Nash equilibria in perfect
information games in extensive form. They are important because they relate to
the rationality of the players. They always exist in infinite games with
continuous real-valued payoffs, but may fail to exist even in simple games with
slightly discontinuous payoffs. This article considers only games whose outcome
functions are measurable in the Hausdorff difference hierarchy of the open sets
(\textit{i.e.} when in the Baire space), and it characterizes the
families of linear preferences such that every game using these preferences has
a subgame perfect equilibrium: the preferences without infinite ascending
chains (of course), and such that for all players and and outcomes
we have . Moreover at
each node of the game, the equilibrium constructed for the proof is
Pareto-optimal among all the outcomes occurring in the subgame. Additional
results for non-linear preferences are presented.Comment: The alternative definition of the difference hierarchy has changed
slightl
Infinite sequential Nash equilibrium
In game theory, the concept of Nash equilibrium reflects the collective
stability of some individual strategies chosen by selfish agents. The concept
pertains to different classes of games, e.g. the sequential games, where the
agents play in turn. Two existing results are relevant here: first, all finite
such games have a Nash equilibrium (w.r.t. some given preferences) iff all the
given preferences are acyclic; second, all infinite such games have a Nash
equilibrium, if they involve two agents who compete for victory and if the
actual plays making a given agent win (and the opponent lose) form a
quasi-Borel set. This article generalises these two results via a single
result. More generally, under the axiomatic of Zermelo-Fraenkel plus the axiom
of dependent choice (ZF+DC), it proves a transfer theorem for infinite
sequential games: if all two-agent win-lose games that are built using a
well-behaved class of sets have a Nash equilibrium, then all multi-agent
multi-outcome games that are built using the same well-behaved class of sets
have a Nash equilibrium, provided that the inverse relations of the agents'
preferences are strictly well-founded.Comment: 14 pages, will be published in LMCS-2011-65
Stable states of perturbed Markov chains
Given an infinitesimal perturbation of a discrete-time finite Markov chain,
we seek the states that are stable despite the perturbation, \textit{i.e.} the
states whose weights in the stationary distributions can be bounded away from
as the noise fades away. Chemists, economists, and computer scientists have
been studying irreducible perturbations built with exponential maps. Under
these assumptions, Young proved the existence of and computed the stable states
in cubic time. We fully drop these assumptions, generalize Young's technique,
and show that stability is decidable as long as is. Furthermore, if
the perturbation maps (and their multiplications) satisfy or , we prove the existence of and compute the stable states and the
metastable dynamics at all time scales where some states vanish. Conversely, if
the big- assumption does not hold, we build a perturbation with these maps
and no stable state. Our algorithm also runs in cubic time despite the general
assumptions and the additional work. Proving the correctness of the algorithm
relies on new or rephrased results in Markov chain theory, and on algebraic
abstractions thereof
TRIDEnT: Building Decentralized Incentives for Collaborative Security
Sophisticated mass attacks, especially when exploiting zero-day
vulnerabilities, have the potential to cause destructive damage to
organizations and critical infrastructure. To timely detect and contain such
attacks, collaboration among the defenders is critical. By correlating
real-time detection information (alerts) from multiple sources (collaborative
intrusion detection), defenders can detect attacks and take the appropriate
defensive measures in time. However, although the technical tools to facilitate
collaboration exist, real-world adoption of such collaborative security
mechanisms is still underwhelming. This is largely due to a lack of trust and
participation incentives for companies and organizations. This paper proposes
TRIDEnT, a novel collaborative platform that aims to enable and incentivize
parties to exchange network alert data, thus increasing their overall detection
capabilities. TRIDEnT allows parties that may be in a competitive relationship,
to selectively advertise, sell and acquire security alerts in the form of
(near) real-time peer-to-peer streams. To validate the basic principles behind
TRIDEnT, we present an intuitive game-theoretic model of alert sharing, that is
of independent interest, and show that collaboration is bound to take place
infinitely often. Furthermore, to demonstrate the feasibility of our approach,
we instantiate our design in a decentralized manner using Ethereum smart
contracts and provide a fully functional prototype.Comment: 28 page
Minkowski Games
We introduce and study Minkowski games. In these games, two players take turns to choose positions in ℝd based on some rules. Variants include boundedness games, where one player wants to keep the positions bounded (while the other wants to escape to infinity), and safety games, where one player wants to stay within a given set (while the other wants to leave it). We provide some general characterizations of which player can win such games, and explore the computational complexity of the associated decision problems. A natural representation of boundedness games yields coNP-completeness, whereas the safety games are undecidable.SCOPUS: cp.pinfo:eu-repo/semantics/publishe
The Brouwer Fixed Point Theorem Revisited
We revisit the investigation of the computational content of the Brouwer Fixed Point Theorem in [7], and answer the two open questions from that work. First, we show that the computational hardness is independent of the dimension, as long as it is greater than 1 (in [7] this was only established for dimension greater than 2). Second, we show that restricting the Brouwer Fixed Point Theorem to L-Lipschitz functions for any L > 1 also does not change the computational strength, which together with prior results establishes a trichotomy for L > 1, L = 1 and L < 1.SCOPUS: cp.kinfo:eu-repo/semantics/publishe
Reduction Techniques for Model Checking and Learning in MDPs
info:eu-repo/semantics/publishe
Dual-band fiber-chip grating coupler in a 300 mm silicon-on-insulator platform and 193 nm deep-UV lithography
4 pags., 5 figs., 1 tab.Surface grating couplers are fundamental building blocks for coupling the light between optical fibers and integrated photonic devices. However, the operational bandwidth of conventional grating couplers is intrinsically limited by their wavelength-dependent radiation angle. The few dual-band grating couplers that have been experimentally demonstrated exhibit low coupling efficiencies and rely on complex fabrication processes. Here we demonstrate for the first time, to the best of our knowledge, the realization of an efficient dual-band grating coupler fabricated using 193 nm deep-ultraviolet lithography for 10 Gbit symmetric passive optical networks. The footprint of the device is 17 × 10 µm. We measured coupling efficiencies of −4.9 and −5.2 dB with a 3-dB bandwidth of 27 and 56 nm at the wavelengths of 1270 and 1577 nm, corresponding to the upstream and downstream channels, respectively.Spanish Ministry of Science, Innovation and Universities
(MICINN) (RTI2018-097957-B-C33, TEC2015-71127-C2-1-R with
FPI Scholarship BES-2016-077798); Community of Madrid - FEDER
funds (S2018/NMT-4326); Horizon 2020 Research and Innovation
Program (Marie Sklodowska-Curie 734331); H2020 European Research
Council (ERC POPSTAR 647342); European Commission (H2020-
ICT-26127-2017 COSMICC 688516); French Industry Ministry
(Nano2022 project under IPCEI program); Agence Nationale de la Recherche
(ANR-MIRSPEC-17-CE09-0041)
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