Children as Refrigerators: When Would Backward Altruism Appear?

Existing economic theories of the evolution of altruism between kinship members usually emphasize the role that altruism can play in facilitating coordination among kin to achieve an otherwise unachievable efficient (in terms of fitness) equilibrium. In this paper, we explore the background environment against which backward altruism was likely to appear. The instinct of sustaining one’s own life drives one to save for one’s old age. However, since social mechanisms were not sophisticated in a primitive society, the rate of return on savings was not high. As a consequence, the resources that remain for the children might be limited. Suppose a cultural menchanism or a mutation caused an individual to become backward-altruistic. She would then expect her children to adopt the same attitude as herself, and take care of her in her old age. With this expectation in mind, she would avoid inefficient savings voluntarily so that her children could obtain more resources. Thus, backward altruism in our model does not play a role of coordination, but helps parents to avoid inefficient resource disposition. We analyze the possible appearance of backward altruism as the rate of return on savings changes.

A decision-theoretic approach to reliable message delivery

We argue that the tools of decision theory need to be taken more seriously in the specification and analysis of systems. We illustrate this by considering a simple problem involving reliable communication, showing how considerations of utility and probability can be used to decide when it is worth sending heartbeat messages and, if they are sent, how often they should be sent.Comment: This is the full version of a paper that appears in the Proceedings of the 12th International Symposium on Distributed Computing, 1998, pp. 89-1

Great Expectations. Part I: On the Customizability of Generalized Expected Utility

We propose a generalization of expected utility that we call generalized EU (GEU), where a decision maker's beliefs are represented by plausibility measures, and the decision maker's tastes are represented by general (i.e.,not necessarily real-valued) utility functions. We show that every agent, ``rational'' or not, can be modeled as a GEU maximizer. We then show that we can customize GEU by selectively imposing just the constraints we want. In particular, we show how each of Savage's postulates corresponds to constraints on GEU.Comment: Preliminary version appears in Proc. 18th International Joint Conference on AI (IJCAI), 2003, pp. 291-29

Great Expectations. Part II: Generalized Expected Utility as a Universal Decision Rule

Many different rules for decision making have been introduced in the literature. We show that a notion of generalized expected utility proposed in Part I of this paper is a universal decision rule, in the sense that it can represent essentially all other decision rules.Comment: Preliminary version appears in Proc. 18th International Joint Conference on AI (IJCAI), 2003, pp. 297-30

Pressure-Temperature Phase Diagram of Multiferroic Ni3V2O8Ni_3V_2O_8

The pressure-temperature phase diagram of multiferroic $Ni_3V_2O_8$ is investigated for hydrostatic pressures up to 2 GPa. The stability range of the ferroelectric phase associated with the incommensurate helical spin order is reduced by pressure and ferroelectricity is completely suppressed at the critical pressure of 1.64 GPa at 6.2 K. Thermal expansion measurements at ambient pressure show strong step-like anomalies of the lattice parameters associated with the lock-in transition into the commensurate paraelectric phase. The expansion anomalies are highly anisotropic, the related volume change is consistent with the high-pressure phase diagram

Large Magneto-Dielectric Effects in Orthorhombic HoMnO3 and YMnO3

We have found a remarkable increase (up to 60 %) of the dielectric constant with the onset of magnetic order at 42 K in the metastable orthorhombic structures of YMnO3 and HoMnO3 that proves the existence of a strong magneto-dielectric coupling in the compounds. Magnetic, dielectric, and thermodynamic properties show distinct anomalies at the onset of the incommensurate magnetic order and thermal hysteresis effects are observed around the lock-in transition temperature at which the incommensurate magnetic order locks into a temperature independent wave vector. The orders of Mn3+ spins and Ho3+ moments both contribute to the magneto-dielectric coupling. A large magneto-dielectric effect was observed in HoMnO3 at low temperature where the dielectric constant can be tuned by an external magnetic field resulting in a decrease of up to 8 % at 7 Tesla. By comparing data for YMnO3 and HoMnO3 the contributions to the coupling between the dielectric response and Mn and Ho magnetic orders are separated.Comment: revised manuscrip

Great Expectations. Part I: On the Customizability of Generalized Expected Utility

Many different rules for decision making have been introduced in the literature. We present a single framework in which to study and compare these rules. This is done by defining expected utility with respect to general expectation structures, where a decision maker's beliefs are represented by plausibility measures and the decision maker's tastes are represented by general (i.e., not necessarily real-valued) utility functions. We call the resulting notion of expected utility generalized EU (GEU) and show that we can represent arbitrary preference relations on acts using GEU. We then show that each of Savage's postulates corresponds to an axiom on GEU. Thus, GEU can be customized to capture postulates of interest.

An asymptotic solution of conical shells of constant thickness Progress report no. 6

Asymptotic solution of thin walled conical shell of revolution under lateral stres

Ferroelectricity in perovskite HoMnO3HoMnO_3 and YMnO3YMnO_3

Ferroelectricity is observed in orthorhombic $HoMnO_3$ and $YMnO_3$ at the magnetic lock-in transitions into an E-type structure or an incommensurate phase with a temperature independent wave vector, respectively. In $HoMnO_3$ the ferroelectric polarization strongly depends on the external magnetic field indicating the involvement of the rare earth moment order in this compound. The results are discussed within the framework of recent theoretical models, in particular the double exchange driven polar displacements predicted for E-type magnetic structures.Comment: 5 pages, 3 figure