The class TFNP, defined by Megiddo and Papadimitriou, consists of multivalued functions with values that are polynomially verifiable and guaranteed to exist. Do we have evidence that such functions are hard, for example, if TFNP is computable in polynomial-time does this imply the polynomial-time hierarchy collapses? We give a relativized negative answer to this question by exhibiting an oracle...

A discussion of the difficulties of prototype theories for describing compositional meaning motivates three experiments that inquire how well-defined concepts fare under paradigms that are commonly interpreted to support the prototype view. The stimulus materials include exemplars of prototype categories (sport, vehicle, fruit, vegetable) previously studied by others, and also exemplars of supp...

We test the effect of players’ moods on their behavior in a gift-exchange game. In the first stage of the game, player 1 chooses a transfer to player 2. In the second stage, player 2 chooses an effort level. Higher effort is more costly for player 2, but it increases player 1’s payoff. We say that player 2 reciprocates if effort is increasing in the transfer received. Player 2 is generous if ef...

Sudden cardiac death remains the single most frequent cause of mortality in the industrialized world [1]. Indeed, approximately every 100 s somebody dies suddenly in the United States alone [2]. Most frequently, ventricular fibrillation (VF) associated with acute myocardial ischemia or infarction is the cause of circulatory collapse [1]. When untreated, VF is lethal within minutes because the a...

Scholarly communication began as an interpersonal exchange of findings between fellow researchers (1). In time, the need arose for a structured, comprehensive, and pragmatic means of communicating scientific knowledge in the form of scholarly journals. Scientists did research for the sake of progress, and journals strived to catalyze the dissemination of research as widely as possible. In the a...

There have been proposals that primordial black hole remnants (BHRs) are the dark matter, but the idea is somewhat vague. We argue here first that the generalized uncertainty principle (GUP) may prevent black holes from evaporating completely, in a similar way that the standard uncertainty principle prevents the hydrogen atom from collapsing. Secondly we note that the hybrid inflation model pro...

This paper focuses on an unsettling example of experimental labour - the Human Landing Catch (HLC). The HLC is a cheap and reliable technique to produce data on mosquito densities in a defined area. It requires only a human volunteer to sit over night with his legs exposed, a headlamp to spot mosquitoes, and a rubber tube and plastic cup to catch them as they come to feed on him. The HLC formed...

levels. This fits well with the observation that the repul-1998). It remains to be seen, however, whether these or 1133.102, 363–375. tions be in mediating guidance decisions at choice points? Another possible site for this mechanism to operate is at the ventral midline of the CNS. In vertebrates, commissural axon crossing of the ventral midline of the spinal cord is regulated by a combination ...