ILLC-LIRa

illc-lira@list.uva.nl

1 participants
582 discussions

LIRa session: Igor Sedlár (tomorrow, Thursday, 31 October 16:30, online)
by LIRa Seminar 30 Oct '24

30 Oct '24

Dear all, We will have our next LIRa session tomorrow, on Thursday, 31 October 16:30. To attend, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Igor Sedlár (Czech Academy of Science) Date and Time: Thursday, October 31st 2024, 16:30-18:00 Venue: online Title: On the Dynamics of Dynamic Attitudes Abstract. In events involving information updates, the source of the update-causing information often determines how the information is received and, consequently, what specific update different agents undergo. Logics in which sources of update-causing information are explicitly modelled, and in which agents' attitudes towards particular pieces of information coming from particular sources are taken into account, are relatively rare in the dynamic epistemic logic literature. An example is provided by Rodenhäuser's logics of information updates with dynamic attitudes, developed in his Ph.D. thesis (ILLC, 2014). We simplify and transpose Rodenhäuser's framework to the setting of Public Announcement Logic, and extend it with mechanisms that represent changes in agents' attitudes towards specific pieces of information from specific sources - dynamics of dynamic attitudes. As this is a work-in-progress talk and mostly programmatic, we focus on examples and present only a handful of technical results, mostly related to completeness via reduction axioms. Hope to see you there! The LIRa team

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LIRa session: Igor Sedlar (Thursday, 31 October 16:30)
by LIRa Seminar 25 Oct '24

25 Oct '24

Dear all, We will have our next LIRa session on Thursday, 31 October 16:30. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Igor Sedlar (Czech Academy of Science) Date and Time: Thursday, October 31st 2024, 16:30-18:00 Venue: online Title: On the Dynamics of Dynamic Attitudes Abstract. In events involving information updates, the source of the update-causing information often determines how the information is received and, consequently, what specific update different agents undergo. Logics in which sources of update-causing information are explicitly modelled, and in which agents' attitudes towards particular pieces of information coming from particular sources are taken into account, are relatively rare in the dynamic epistemic logic literature. An example is provided by Rodenhäuser's logics of information updates with dynamic attitudes, developed in his Ph.D. thesis (ILLC, 2014). We simplify and transpose Rodenhäuser's framework to the setting of Public Announcement Logic, and extend it with mechanisms that represent changes in agents' attitudes towards specific pieces of information from specific sources - dynamics of dynamic attitudes. As this is a work-in-progress talk and mostly programmatic, we focus on examples and present only a handful of technical results, mostly related to completeness via reduction axioms. Hope to see you there! The LIRa team

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Joint LIRa and DIP session: Igor Douven (tomorrow, Thursday, 24 October 16:30)
by LIRa Seminar 23 Oct '24

23 Oct '24

Dear all, We will have a joint LIRa and DIP session tomorrow, on Thursday, 24 October 16:30. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. This will be a joint session together with the DIP Colloquium. Speaker: Igor Douven (IHPST/CNRS/Panthéon Sorbonne University) Date and Time: Thursday, October 24th 2024, 16:30-18:00 Venue: KdVI seminar room F3.20 in Science Park 107 Title: Reinforcement Learning as Meta-induction Abstract : The meta-inductive justification of induction is usually regarded as a social learning strategy. But, pre-theoretically, induction can be justified even for an isolated thinker, incapable of, or unwilling to engage in, any social interactions. This paper presents reinforcement learning (RL) as a natural meta-inductive strategy for such isolated thinkers. The meta-inductive reinforcement learner learns to choose an optimal prediction method among the available methods by applying trial and error learning. We use computer simulations to show that, under plausible assumptions, trial and error learning indeed leads the thinker to favor induction over non-inductive predictive methods. Under further plausible assumptions, the meta-inductive thinker itself is even seen to outperform all object-level methods. The results are shown to hold true in both stationary and non-stationary environments. (This is joint work with Gerhard Schurz.) Hope to see you there! The LIRa team

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Joint LIRa and DIP session: Igor Douven (Thursday, 24 October 16:30)
by LIRa Seminar 19 Oct '24

19 Oct '24

Dear all, We will have a joint LIRa and DIP session on Thursday, 24 October 16:30. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. This will be a joint session together with the DIP Colloquium. Speaker: Igor Douven (IHPST/CNRS/Panthéon Sorbonne University) Date and Time: Thursday, October 24th 2024, 16:30-18:00 Venue: KdVI seminar room F3.20 in Science Park 107 Title: Reinforcement Learning as Meta-induction Abstract. The meta-inductive justification of induction is usually regarded as a social learning strategy. But, pre-theoretically, induction can be justified even for an isolated thinker, incapable of, or unwilling to engage in, any social interactions. This paper presents reinforcement learning (RL) as a natural meta-inductive strategy for such isolated thinkers. The meta-inductive reinforcement learner learns to choose an optimal prediction method among the available methods by applying trial and error learning. We use computer simulations to show that, under plausible assumptions, trial and error learning indeed leads the thinker to favor induction over non-inductive predictive methods. Under further plausible assumptions, the meta-inductive thinker itself is even seen to outperform all object-level methods. The results are shown to hold true in both stationary and non-stationary environments. (This is joint work with Gerhard Schurz.) Hope to see you there! The LIRa team

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LIRa session: Mina Young Pedersen (tomorrow, Thursday, 17 October 16:30)
by LIRa Seminar 16 Oct '24

16 Oct '24

Dear all, We will have our next LIRa session tomorrow, on Thursday, 17 October 16:30. To attend, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Mina Young Pedersen (University of Bergen) Date and Time: Thursday, October 17th 2024, 16:30-18:00 Venue: online Title: Logics of malicious and abnormal behavior in social networks. Abstract. This talk concerns agents in multi-agent systems who act out of the ordinary and/or maliciously for their own gain. Analyzing these types of agents can not only give us valuable information about agents’ potential power to disrupt, but also about the safety of systems in which they act. Specifically, I will talk about using modal logics for social networks to reason about malicious and abnormal behavior. I will give an example of such a study where we use a temporal logic to follow a social network as it evolves through time. We see how one can use model checking to detect a particular type of agent, namely social bots, which are computer programs that act like human users on social media platforms. The talk is based on joint work with Marija Slavkovik and Sonja Smets. Hope to see you there! The LIRa team

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LIRa session: Mina Young Pedersen (Thursday, 17 October 16:30, online)
by LIRa Seminar 11 Oct '24

11 Oct '24

Dear all, We will have our next LIRa session on Thursday, 17 October 16:30. To attend, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Mina Young Pedersen (University of Bergen) Date and Time: Thursday, October 17th 2024, 16:30-18:00 Venue: online Title: Logics of malicious and abnormal behavior in social networks. Abstract. This talk concerns agents in multi-agent systems who act out of the ordinary and/or maliciously for their own gain. Analyzing these types of agents can not only give us valuable information about agents’ potential power to disrupt, but also about the safety of systems in which they act. Specifically, I will talk about using modal logics for social networks to reason about malicious and abnormal behavior. I will give an example of such a study where we use a temporal logic to follow a social network as it evolves through time. We see how one can use model checking to detect a particular type of agent, namely social bots, which are computer programs that act like human users on social media platforms. The talk is based on joint work with Marija Slavkovik and Sonja Smets. Hope to see you there! The LIRa team

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LIRa session: Giuliano Rosella (tomorrow, Thursday, 3 October 16:30, online only)
by LIRa Seminar 02 Oct '24

02 Oct '24

Dear all, We will have our next LIRa session tomorrow, on Thursday, 3 October 16:30. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Giuliano Rosella (University of Turin) Date and Time: Thursday, October 3rd 2024, 16:30-18:00 Venue: online Title: The algebra of Lewis’s counterfactuals and their duality theory Abstract. The logico-algebraic study of Lewis’s hierarchy of variably strict conditional logics has been essentially unexplored, hindering our understanding of their mathematical foundations, and the connections with other logical systems. This work aims to fill this gap by providing a comprehensive logico-algebraic analysis of Lewis’s logics. We begin by introducing novel finite axiomatizations for varying strengths of Lewis’s logics, distinguishing between global and local consequence relations on Lewisian sphere models. We then demonstrate that the global consequence relation is strongly algebraizable in terms of a specific class of Boolean algebras with a binary operator representing the counterfactual implication. In contrast, we show that the local consequence relation is generally not algebraizable, although it can be characterized as the degree-preserving logic over the same algebraic models. Further, we delve into the algebraic semantics of Lewis’s logics, developing two dual equivalences with respect to particular topological spaces. In more details, we show a duality with respect to the topological version of Lewis’s sphere models, and also with respect to Stone spaces with a selection function; using the latter, we demonstrate the strong completeness of Lewis’s logics with respect to sphere models. Finally, we draw some considerations concerning the limit assumption over sphere models. Hope to see you there! The LIRa team

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LIRa session: Giuliano Rosella (Thursday, 3 October 16:30)
by LIRa Seminar 28 Sep '24

28 Sep '24

Dear all, We will have our next LIRa session on Thursday, 3 October 16:30. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Giuliano Rosella (University of Turin) Date and Time: Thursday, October 3rd 2024, 16:30-18:00 Venue: online Title: The algebra of Lewis’s counterfactuals and their duality theory Abstract. The logico-algebraic study of Lewis’s hierarchy of variably strict conditional logics has been essentially unexplored, hindering our understanding of their mathematical foundations, and the connections with other logical systems. This work aims to fill this gap by providing a comprehensive logico-algebraic analysis of Lewis’s logics. We begin by introducing novel finite axiomatizations for varying strengths of Lewis’s logics, distinguishing between global and local consequence relations on Lewisian sphere models. We then demonstrate that the global consequence relation is strongly algebraizable in terms of a specific class of Boolean algebras with a binary operator representing the counterfactual implication. In contrast, we show that the local consequence relation is generally not algebraizable, although it can be characterized as the degree-preserving logic over the same algebraic models. Further, we delve into the algebraic semantics of Lewis’s logics, developing two dual equivalences with respect to particular topological spaces. In more details, we show a duality with respect to the topological version of Lewis’s sphere models, and also with respect to Stone spaces with a selection function; using the latter, we demonstrate the strong completeness of Lewis’s logics with respect to sphere models. Finally, we draw some considerations concerning the limit assumption over sphere models. Hope to see you there! The LIRa team

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LIRa session: Rebecca Reiffenhäuser (tomorrow, Thursday, 19 September 16:30)
by LIRa Seminar 18 Sep '24

18 Sep '24

Dear all, We will have our next LIRa session tomorrow, on Thursday, 19 September 16:30. This talk will be hybrid, with the speaker on location. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Rebecca Reiffenhäuser (ILLC, University of Amsterdam) Date and Time: Thursday, September 19th 2024, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: How to sell your items online - with almost no prior info. Abstract. The problem of allocating a set of items to a set of buyers in a way that maximizes an objective, like the overall valuation of participants for the items they receive (social welfare), is a central setting with numerous applications. We consider the harder, but very prevalent case where buyers/bids arrive over time in some fixed order, and decisions have to be made immediately (online) on their arrival. It is impossible to get close to the optimal value that would be achievable for a prophet who can see future participants valuations beforehand, and giving all items to some random person is actually the best you can do. Therefore, we additionally assume to get a tiny piece of information on each of the future participants beforehand: For every buyer to arrive, we assume to have a single sample of what his valuation function might be, e.g. from when he participated in an earlier auction. We show that this suffices to achieve an expected, constant-factor approximation to the value of the future-seeing prophet for buyers with XOS valuation functions, and also consider the case that buyers might misreport their values strategically – which so far we can only deal with if we have some more samples. (Based on joint work with Paul Duetting, Thomas Kesselheim, Brendan Lucier and Sahil Singla, to appear in FOCS 2024.) Hope to see you there! The LIRa team

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LIRa session: Rebecca Reiffenhäuser (Thursday, 19 September 16:30)
by LIRa Seminar 14 Sep '24

14 Sep '24

Dear all, We will have our next LIRa session on Thursday, 19 September 16:30. This talk will be hybrid, with the speaker on location. To attend online, please use our recurring zoom link: https://uva-live.zoom.us/j/89230639823?pwd=YWJuSnJmTDhXcWhmd1ZkeG5zb0o5UT09 (Meeting ID: 892 3063 9823, Passcode: 421723) You can find the details of the talk below. Speaker: Rebecca Reiffenhäuser (ILLC, University of Amsterdam) Date and Time: Thursday, September 19th 2024, 16:30-18:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: How to sell your items online - with almost no prior info. Abstract. The problem of allocating a set of items to a set of buyers in a way that maximizes an objective, like the overall valuation of participants for the items they receive (social welfare), is a central setting with numerous applications. We consider the harder, but very prevalent case where buyers/bids arrive over time in some fixed order, and decisions have to be made immediately (online) on their arrival. It is impossible to get close to the optimal value that would be achievable for a prophet who can see future participants valuations beforehand, and giving all items to some random person is actually the best you can do. Therefore, we additionally assume to get a tiny piece of information on each of the future participants beforehand: For every buyer to arrive, we assume to have a single sample of what his valuation function might be, e.g. from when he participated in an earlier auction. We show that this suffices to achieve an expected, constant-factor approximation to the value of the future-seeing prophet for buyers with XOS valuation functions, and also consider the case that buyers might misreport their values strategically – which so far we can only deal with if we have some more samples. (Based on joint work with Paul Duetting, Thomas Kesselheim, Brendan Lucier and Sahil Singla, to appear in FOCS 2024.) Hope to see you there! The LIRa team

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