讲座人：Dr. Jeremy Seligman (University of Auckland)

讲座时间地点：5月28日15:10-18:00, 理教311

讲座摘要：

Secret tweets and network discovery

You are a secret agent with a secret $S$ that you would like to transmit to a fellow agent $a$ unobtrusively using a very public network like Twitter. Any information you tweet will be received by your followers on the network. You correctly assume that they will send the message on to their followers (retweet it) if and only if it does not conflict with any information they already possess. With luck,your message will be tweeted through the network until it eventually reachers $a$. Under what conditions is it possible for you to convey $S$ to $a$ in this way,without other agents in the network learning this information? Clearly,you cannot tweet $S$ itself,but if,for example,$a$ is the only agent to knows that $K$ then the message `if $K$ then $S$’ may work,if there is a suitable path from you to $a$. To know whether you can succeed or not and what to tweet,you need to know something about the network and the information already possessed by the other agents. But you can learn something about this with a test tweet. If,for example,you know that you have two followers $b$ and $c$ and only $b$ believes $P$ and then you tweet the message $ eg P$ then if,after a certain length of time,someone tweets $P$ to you,you know that there is a loop back to you via $c$. This talk will report on recent joint work on these and similar questions with Mostafa Raziebrahimsaraei.

Past, Present and Future: the logic and philosophy of Arthur Prior

Fascinated with the concept of pre-destination, New Zealand logician Arthur Prior (1914-1969) initiated the first systematic investigation into the logic of time.  His clarity of thought and sharp distinctions are a model of philosophical enquiry and many of his ideas subsequently became a theoretical foundation for research on time in philosophy, linguistics and computer science. This lecture will be a gentle introduction to some of these ideas, against the background of the life of “an exuberant, playful man of seemingly inexhaustible vitality” (Copeland 2007) held in celebration of his centenary year.