Motivic zeta function via dlt modification

Given a smooth variety $X$ and a regular function $f$ on it, by considering the dlt modification, we define the dlt motivic zeta function $Z^{\rm dlt}_{\rm mot}(s)$ which does not depend on the choice of the dlt modification.Comment: 11 page

Starshaped locally convex hypersurfaces with prescribed curvature and boundary

In this paper we find strictly locally convex hypersurfaces in $\mathbb{R}^{n+1}$ with prescribed curvature and boundary. The main result is that if the given data admits a strictly locally convex radial graph as a subsolution, we can find a radial graph realizing the prescribed curvature and boundary. As an application we show any smooth domain on the boundary of a compact strictly convex body can be deformed to a smooth hypersurface with the same boundary (inside the convex body) and realizing any prescribed curvature function smaller than the curvature of the body.Comment: 24 pages. References updated. Published in The Journal of Geometric Analysi

Is Meat the New Tobacco? Regulating Food Demand in the Age of Climate Change

Switching from a meat-heavy to a plant-based diet is one of the highest-impact lifestyle changes for climate mitigation and adaptation. Conventional demand-side energy policy has focused on increasing consumption of efficient machines and fuels. Regulating food demand has key advantages. First, food consumption is biologically constrained, thus switching to more efficient foods avoids unintended consequences of switching to more efficient machines, like higher overall energy consumption. Second, food consumption, like smoking, is primed for norm- shifting because it occurs in socially conspicuous environments. While place-based bans and information regulation were essential in lowering the prevalence of smoking, the same strategies may be even more effective in reducing meat demand. Several policy reforms can be implemented at the federal level, from reform of food marketing schemes to publicly subsidized meal programs

The essential skeleton of a degeneration of algebraic varieties

In this paper, we explore the connections between the Minimal Model Program and the theory of Berkovich spaces. Let $k$ be a field of characteristic zero and let $X$ be a smooth and proper $k((t))$-variety with semi-ample canonical divisor. We prove that the essential skeleton of $X$ coincides with the skeleton of any minimal $dlt$-model and that it is a strong deformation retract of the Berkovich analytification of $X$. As an application, we show that the essential skeleton of a Calabi-Yau variety over $k((t))$ is a pseudo-manifold.Comment: To appear in American Journal of Mathematic

Poles of maximal order of motivic zeta functions

We prove a 1999 conjecture of Veys, which says that the opposite of the log canonical threshold is the only possible pole of maximal order of Denef and Loeser's motivic zeta function associated with a germ of a regular function on a smooth variety over a field of characteristic zero. We apply similar methods to study the weight function on the Berkovich skeleton associated with a degeneration of Calabi-Yau varieties. Our results suggest that the weight function induces a flow on the non-archimedean analytification of the degeneration towards the Kontsevich-Soibelman skeleton.Comment: to appear in Duke Mathematical Journa

On the Feasibility of Linear Interference Alignment for MIMO Interference Broadcast Channels with Constant Coefficients

In this paper, we analyze the feasibility of linear interference alignment (IA) for multi-input-multi-output (MIMO) interference broadcast channel (MIMO-IBC) with constant coefficients. We pose and prove the necessary conditions of linear IA feasibility for general MIMO-IBC. Except for the proper condition, we find another necessary condition to ensure a kind of irreducible interference to be eliminated. We then prove the necessary and sufficient conditions for a special class of MIMO-IBC, where the numbers of antennas are divisible by the number of data streams per user. Since finding an invertible Jacobian matrix is crucial for the sufficiency proof, we first analyze the impact of sparse structure and repeated structure of the Jacobian matrix. Considering that for the MIMO-IBC the sub-matrices of the Jacobian matrix corresponding to the transmit and receive matrices have different repeated structure, we find an invertible Jacobian matrix by constructing the two sub-matrices separately. We show that for the MIMO-IBC where each user has one desired data stream, a proper system is feasible. For symmetric MIMO-IBC, we provide proper but infeasible region of antenna configurations by analyzing the difference between the necessary conditions and the sufficient conditions of linear IA feasibility.Comment: 14 pages, 3 figures, accepted by IEEE Trans. on Signal Processin