Anonymity and Information Hiding in Multiagent Systems

We provide a framework for reasoning about information-hiding requirements in multiagent systems and for reasoning about anonymity in particular. Our framework employs the modal logic of knowledge within the context of the runs and systems framework, much in the spirit of our earlier work on secrecy [Halpern and O'Neill 2002]. We give several definitions of anonymity with respect to agents, actions, and observers in multiagent systems, and we relate our definitions of anonymity to other definitions of information hiding, such as secrecy. We also give probabilistic definitions of anonymity that are able to quantify an observer s uncertainty about the state of the system. Finally, we relate our definitions of anonymity to other formalizations of anonymity and information hiding, including definitions of anonymity in the process algebra CSP and definitions of information hiding using function views.Comment: Replacement. 36 pages. Full version of CSFW '03 paper, submitted to JCS. Made substantial changes to Section 6; added references throughou

Monetary and fiscal impacts on exchange rates

Foreign exchange rates ; Fiscal policy ; Monetary policy ; Budget deficits ; Dollar, American

Classical reflections on the deficit

Deficit financing ; Debt management ; Crowding out (Economics) ; Interest rates

Recurrent chest infections in two young non-smoker men

Pulmonary mucinous cystic carcinomas are rare salivary gland type carcinomas of the lung. They form part of a wide spectrum of mucin secreting glandular mixed type tumours. They comprise 0.1 – 0.2% of all lung tumours. They occur more frequently in young patients and present with cough or recurrent chest infections and therefore may be easily misdiagnosed. Since treatment depends fully on complete surgical resection early diagnosis is essential. Even with treatment the 10-year survival is quoted at 53%. We describe two cases of such rare tumours both of who underwent curative surgical resection. Both patients were younger than 35 years old and presented with recurrent chest infections. The patients were followed for up to eight years and the outcome recorded. A literature search confirms the occurrence in younger patients, who often present with pneumonias and that surgery is the only hope for cure.peer-reviewe

Martingales, the efficient market hypothesis, and spurious stylized facts

The condition for stationary increments, not scaling, detemines long time pair autocorrelations. An incorrect assumption of stationary increments generates spurious stylized facts, fat tails and a Hurst exponent Hs=1/2, when the increments are nonstationary, as they are in FX markets. The nonstationarity arises from systematic uneveness in noise traders’ behavior. Spurious results arise mathematically from using a log increment with a ‘sliding window’. We explain why a hard to beat market demands martingale dynamics , and martingales with nonlinear variance generate nonstationary increments. The nonstationarity is exhibited directly for Euro/Dollar FX data. We observe that the Hurst exponent Hs generated by the using the sliding window technique on a time series plays the same role as does Mandelbrot’s Joseph exponent. Finally, Mandelbrot originally assumed that the ‘badly behaved second moment of cotton returns is due to fat tails, but that nonconvergent behavior is instead direct evidence for nonstationary increments. Summarizing, the evidence for scaling and fat tails as the basis for econophysics and financial economics is provided neither by FX markets nor by cotton price data