arXiv subjects

Ajay C. Ramadoss

Publications and source records attributed to Ajay C. Ramadoss.

23 records · Page 2Linked to original sources

arXiv2008

Integration over complex manifolds via Hochschild homology

Given a holomorphic vector bundle $\cale$ on a connected compact complex manifold X, [FLS] construct a $\compl$-linear functional $I_{\cale}$ on $\hh{2n}{\compl}$. This is done by constructing a linear functional on the 0-th completed Hochschild homology $\choch{0}{(\dif(\cale))}$ of the sheaf of holomorphic differential operators on $\cale$ using topological quantum mechanics. They show that this functional is $\int_X$ if $\cale$ has non zero Euler characteristic. They conjecture that this functional is $\int_X$ for all $\cale$. A subsequent work [Ram] by the author proved that the linear functional $I_{\cale}$ is independent of the vector bundle $\cale$. This note builds upon the work in [Ram] to prove that $I_{\cale}=\int_X$ for an arbitrary holomorphic vector bundle $\cale$ on an arbitrary connected compact complex manifold X. This is done using an argument that is very natural from the geometric point of view. This argument enables us to extend the construction in [FLS] to a construction of a linear functional $I_{\cale}$ on $\text{H}^{2n}_{c}(Y,\compl)$ for an arbitrary holomorphic vector bundle $\cale$ on an arbitrary connected complex manifold Y and prove that $I_{\cale} = \int_Y$. We also generalize a result of [Ram] pertaining to "cyclic homology analogs" of $I_{\cale}$.

math.AG↗

arXiv2008

The big Chern classes and the Chern character

Let $X$ be a smooth scheme over a field of characteristic 0. Let $\dd^{\bullet}(X)$ be the complex of polydifferential operators on $X$ equipped with Hochschild co-boundary. Let $L(\dd^1(X))$ be the free Lie algebra generated over $\strc$ by $\dd^1(X)$ concentrated in degree 1 equipped with Hochschild co-boundary. We have a symmetrization map $I: \oplus_k \sss^k(L(\dd^1(X))) \rar \dd^{\bullet}(X)$. Theorem 1 of this paper measures how the map $I$ fails to commute with multiplication. A consequence of Theorem 1 and Theorem 2 is Corollary 1, a result "dual" to Theorem 1 of Markarian [3] that measures how the Hochschild-Kostant-Rosenberg quasi-isomorphism fails to commute with multiplication. In order to understand Theorem 1 conceptually, we prove a theorem (Theorem 3) stating that $\dd^{\bullet}(X)$ is the universal enveloping algebra of $T_X[-1]$ in $\dcat$. An easy consequence of Theorem 3 is Theorem 4, which interprets the Chern character $E$ as the "character of the representation $E$ of $T_X[-1]$" and gives a description of the big Chern classes of $E$. Finally, Theorem 4 along with Theorem 1 is used to give an explicit formula (Theorem 5) expressing the big Chern classes of $E$ in terms of the components of the Chern character of $E$.

math.AG↗

arXiv2008

Some notes on the Feigin Losev Shoikhet integral conjecture

Given a vector bundle $\mathcal E$ on a connected compact complex manifold $X$, [FLS] use a notion of completed Hochschild homology $\hat{\text{HH}}$ of $\text{Diff}(\mathcal E)$ such that $\hat{\text{HH}}_0(\text{Diff}(\mathcal E))$ is isomorphic to $\text{H}^{2n}(X, \mathbb C)$. On the other hand, they construct a trace on $\hat{\text{HH}}_0(\text{Diff}(\mathcal E))$. This therefore gives to a linear functional on $\text{H}^{2n}(X, \mathbb C)$. They show that this functional is $\int_X$ if $\mathcal E$ has non zero Euler characteristic. They conjecture that this functional is $\int_X$ for all $\mathcal E$. These notes prove the integral conjecture in [FLS] for compact complex manifolds having at least one vector bundle with non zero Euler characteristic.

math.QA↗

arXiv2007

The relative Riemann-Roch theorem from Hochschild homology

This write up attempts to clarify a preprint by Markarian [2] which proves This paper attempts to clarify a preprint of Markarian [2]. The preprint by Markarian [2] proves the relative Riemann-Roch theorem using a result describing how the HKR map fails to respect comultiplication. This paper elaborates on the core computations in [2]. These computations show that the HKR map twisted by the square root of the Todd genus "almost preserves" the Mukai pairing. This settles a part of a conjecture of Caldararu[3]. The relative Riemann-Roch theorem follows from this and a result of Caldararu[4].

math.AG↗

arXiv2007

On the nonexistence of certain morphisms from Grassmannian to Grassmannian in characteristic 0

Here, we utilize facts about the big Chern classes discovered by M. Kapranov and independently by M. V. Nori to prove certain results about the nonexistence of certain morphisms from Grassmannian to Grassmannian in characteristic 0. In particular, we show that the filtration F_. on CH^l(X) where F_rCH^l(X) is the linear span of ch_l(V) for all vector bundles V of rank <=r is nontrivial as a theory by showing that for a fixed l>=2, for infinitely many r, for a Grassmannian of r dimensional quotient spaces in an n dimensional vector space (n sufficiently large) over a field of charactersitic 0, ch_l(Q) is in F_rCH^l(G(r,n)) but not in F^(r-1)CH^l(G(r,n)) where Q is the universal quotient bundle of the Grassmannian G(r,n). Separately but using similar methods, we show that for r>=2, if Q denotes the universal quotient bundle of the Grassmannian of r dimensional quotients G(r,n), n>=2r+1, then the class [ψ^pQ] can never be equal to the class of a genuine vector bundle in K(G). In parallel, we obtain a formula for the bid Chern classes in terms of the ch_l. This leads to the identification of proper subfunctors of the Hodge functors H^q(X, Ω^p) in characteristic 0.

math.AG↗