Serre–Tate theory for Calabi–Yau varieties

Classical Serre–Tate theory describes deformations of ordinary abelian varieties. It implies that every such variety has a canonical lift to characteristic zero and equips the base of its universal deformation with a Frobenius lifting and canonical multiplicative coordinates. A variant of this theory has been obtained for ordinary K3 surfaces by Nygaard and Ogus. In this paper, we construct canonical liftings modulo p 2 {p^{2}} of varieties with trivial canonical class which are ordinary in the weak sense that the Frobenius acts bijectively on the top cohomology of the structure sheaf. Consequently, we obtain a Frobenius lifting on the moduli space of such varieties. The quite explicit construction uses Frobenius splittings and a relative version of Witt vectors of length two. If the variety has unobstructed deformations and bijective first higher Hasse–Witt operation, the Frobenius lifting gives rise to canonical coordinates. One of the key features of our liftings is that the crystalline Frobenius preserves the Hodge filtration. We also extend Nygaard’s approach from K3 surfaces to higher dimensions, and show that no non-trivial families of such varieties exist over simply connected bases with no global one-forms.

Some New Variants of Relative Regularity via Regularly Closed Sets

Every topological property can be associated with its relative version in such a way that when smaller space coincides with larger space, then this relative property coincides with the absolute one. This notion of relative topological properties was introduced by Arhangel’skii and Ganedi in 1989. Singal and Arya introduced the concepts of almost regular spaces in 1969 and almost completely regular spaces in 1970. In this paper, we have studied various relative versions of almost regularity, complete regularity, and almost complete regularity. We investigated some of their properties and established relationships of these spaces with each other and with the existing relative properties.

Inflation and Exchange Rates: An International Examination of Relative Purchasing Power Parity

Purchasing power parity (PPP) is an old and controversial proposition in economic literature. It is based on the law of one price, which argues that, after adjusting for the exchange rate, domestic and foreign price levels are equal. The relative version of PPP argues that exchange rate changes depend on the differential between domestic and foreign inflation rates. The absolute PPP version is based on restrictive assumptions that prevent it to hold in the short run. However, several studies support the validity of the relative PPP proposition in the long run. It is often observed that countries with persistently high inflation experience weak currencies. Our empirical testing using impulse response functions derived from a VAR model for eight countries provide mixed results. In six out of eight selected countries, relative PPP is supported by data in the long run.

An Open and Shut Case: Epistemic Closure in the Manifest Image

The epistemic closure principle says that knowledge is closed under known entailment. The closure principle is deeply implicated in numerous core debates in contemporary epistemology. Closure’s opponents claim that there are good theoretical reasons to abandon it. Closure’s proponents claim that it is a defining feature of ordinary thought and talk and, thus, abandoning it is radically revisionary. But evidence for these claims about ordinary practice has thus far been anecdotal. In this paper, I report five studies on the status of epistemic closure in ordinary practice. Despite decades of widespread assumptions to the contrary in philosophy, ordinary practice is ambivalent about closure. Ordinary practice does not endorse an unqualified version of the epistemic closure principle, although it might endorse a source-relative version of the principle. In particular, whereas inferential knowledge is not viewed as closed under known entailment, perceptual knowledge might be.

Relative vertex asphericity

Diagrammatic reducibility DR and its generalization, vertex asphericity VA, are combinatorial tools developed for detecting asphericity of a 2-complex. Here we present tests for a relative version of VA that apply to pairs of 2-complexes $(L,K)$ , where K is a subcomplex of L. We show that a relative weight test holds for injective labeled oriented trees, implying that they are VA and hence aspherical. This strengthens a result obtained by the authors in 2017 and simplifies the original proof.

Monotone Lagrangians in Flag Varieties

In this paper, we give a formula for the Maslov index of a gradient holomorphic disk, which is a relative version of the Chern number formula of a gradient holomorphic sphere for a Hamiltonian $S^1$-action. Using the formula, we classify all monotone Lagrangian fibers of Gelfand–Cetlin systems on partial flag manifolds.

The relative monoidal center and tensor products of monoidal categories

This paper develops a theory of monoidal categories relative to a braided monoidal category, called augmented monoidal categories. For such categories, balanced bimodules are defined using the formalism of balanced functors. It is shown that there exists a monoidal structure on the relative tensor product of two augmented monoidal categories which is Morita dual to a relative version of the monoidal center. In examples, a category of locally finite weight modules over a quantized enveloping algebra is equivalent to the relative monoidal center of modules over its Borel part. A similar result holds for small quantum groups, without restricting to locally finite weight modules. More generally, for modules over bialgebras inside a braided monoidal category, the relative center is shown to be equivalent to the category of Yetter–Drinfeld modules inside the braided category. If the braided category is given by modules over a quasitriangular Hopf algebra, then the relative center corresponds to modules over a braided version of the Drinfeld double (i.e. the double bosonization in the sense of Majid) which are locally finite for the action of the dual.

Donaldson–Thomas invariants versus intersection cohomology of quiver moduli

The main result of this paper is the statement that the Hodge theoretic Donaldson–Thomas invariant for a quiver with zero potential and a generic stability condition agrees with the compactly supported intersection cohomology of the closure of the stable locus inside the associated coarse moduli space of semistable quiver representations. In fact, we prove an even stronger result relating the Donaldson–Thomas “function” to the intersection complex. The proof of our main result relies on a relative version of the integrality conjecture in Donaldson–Thomas theory. This will be the topic of the second part of the paper, where the relative integrality conjecture will be proven in the motivic context.

On the vanishing of relative negative K-theory

In this paper, we study the relative negative [Formula: see text]-groups [Formula: see text] of a map [Formula: see text] of schemes. We prove a relative version of Weibel’s conjecture; i.e. if [Formula: see text] is a smooth affine map of Noetherian schemes with [Formula: see text], then [Formula: see text] for [Formula: see text] and the natural map [Formula: see text] is an isomorphism for all [Formula: see text] and [Formula: see text] We also prove a vanishing result for relative negative [Formula: see text]-groups of a subintegral map.