A characterization of cooperative TU-games with large monotonic core

Cooperative TU-games with large core were introduced by Sharkey (1982) and the concept of Population Monotonic Allocation Scheme was defined by Sprumont (1990). Linking these two concepts, Moulin (1990) introduces the notion of large monotonic core giving a characterization for three-player games. In this paper we prove that all games with large monotonic core are convex. We give an effective criterion to determine whether a game has large monotonic core and, as a consequence, we obtain a characterization for the four-player case.aspiration, pmas, cooperative games, monotonic core

RACIAL MINORITIES IN U.S. HISTORY TEXTBOOKS: A CASE FOR A MORE SYSTEMATIC APPROACH TO TEXTBOOK EVALUATION

A few decades ago, textbook adoption proceedings were relatively dull affairs. Present at these meetings were political, business, and labor interest group representatives who were primarily concerned with the treatment their constituencies received in textbooks, especially social studies texts. Expressing common concerns, board members and traditional interest group representatives only occasionally debated what ought to be included in social studies texts. The dealings rarely bordered on the sensational and, in most cases, resulted in minimal discussion and acceptance of texts recommended for adoption by a board\u27s textbook committee

Galactic PeV neutrinos from dark matter annihilation

The IceCube Neutrino Observatory has observed highly energetic neutrinos in excess of the expected atmospheric neutrino background. It is intriguing to consider the possibility that such events are probing physics beyond the standard model. In this context, $\mathcal{O}$(PeV) dark matter particles decaying to neutrinos have been considered while dark matter annihilation has been dismissed invoking the unitarity bound as a limiting factor. However, the latter claim was done ignoring the contribution from dark matter substructure, which for PeV Cold Dark Matter would extend down to a free streaming mass of $\mathcal{O}$($10^{-18}$M$_\odot$). Since the unitarity bound is less stringent at low velocities, ($\sigma_{\rm ann}$v)$\leq4\pi/m_\chi^2v$, then, it is possible that these cold and dense subhalos would contribute dominantly to a dark-matter-induced neutrino flux and easily account for the events observed by IceCube. A Sommerfeld-enhanced dark matter model can naturally support such scenario. Interestingly, the spatial distribution of the events shows features that would be expected in a dark matter interpretation. Although not conclusive, 9 of the 37 events appear to be clustered around a region near the Galactic Center while 6 others spatially coincide, within the reported angular errors, with 5 of 26 Milky Way satellites. However, a simple estimate of the probability of the latter occurring by chance is $\sim35\%$. More events are needed to statistically test this hypothesis. PeV dark matter particles are massive enough that their abundance as standard thermal relics would overclose the Universe. This issue can be solved in alternative scenarios, for instance if the decay of new massive unstable particles generates significant entropy reheating the Universe to a slightly lower temperature than the freeze-out temperature, $T_{\rm RH} \lesssim T_{\rm f}\sim4\times10^4$~GeV.Comment: 14 pages, 3 figures, accepted for publication in Physical Review D; added: new IceCube data, Fig. 3 and related discussio

Manual D\u27Enigmistica

My obsession for playing with words was ignited nearly ten years ago, with the discovery of a palindrome in a Julio Cortazar tale. Since then, I have devoted myself to accumulating historical material relating to word games, as well as to creating new ones. Undeniably, an inherent element of such an obsession is the opportunity offered to the writer to master language and manipulate it in new ways

Evidence of radiation-driven Landau states in 2D electron systems: magnetoresistance oscillations phase shift

We provide the ultimate explanation of one of the core features of microwave-induced magnetoresistance oscillations in high mobility two dimensional electron systems: the 1/4-cycle phase shift of minima. We start with the radiation-driven electron orbits model with the novel concept of scattering flight-time between Landau states. We calculate the extrema and nodes positions obtaining an exact coincidence with the experimental ones. The main finding is that the physical origin of the phase shift is a delay of $\frac{\pi}{2}$ of the radiation-driven Landau guiding center with respect to radiation, demonstrating the oscillating nature of the irradiated Landau states. We analyze the dependence of this minima on radiation frequency and power and its possible shift with the quality of the sampleComment: 5 pages, 3 figure