arXiv subjects
Publications and source records attributed to Shaun V. Ault.
Using lattice path counting arguments, we reproduce a well known formula for the number of standard Young tableaux. We also produce an interesting new formula for tableaux of height $\leq 3$ using the Fourier methods of Ault and Kicey.
The symmetric homology of a unital associative algebra $A$ over a commutative ground ring $k$, denoted $HS_*(A)$, is defined using derived functors and the symmetric bar construction of Fiedorowicz. In this paper we show that $HS_*(A)$ admits homology operations and a Pontryagin product structure making $HS_*(A)$ an associative commutative graded algebra. This is done by finding an explicit $E_{\infty}$ structure on the standard chain groups that compute symmetric homology.
A circular Pascal array is a periodization of the familiar Pascal's triangle. Using simple operators defined on periodic sequences, we find a direct relationship between the ranges of the circular Pascal arrays and numbers of certain lattice paths within corridors, which are related to Dyck paths. This link provides new, short proofs of some nontrivial formulas found in the lattice-path literature.
In this short note, we use Robert Bruner's $\mathcal{A}(1)$-resolution of $P = \mathbb{F}_2[t]$ to shed light on the Hit Problem. In particular, the reduced syzygies $P_n$ of $P$ occur as direct summands of $\widetilde{P}^{\otimes n}$, where $\widetilde{P}$ is the augmentation ideal of the map $P \to \mathbb{F}_2$. The complement of $P_n$ in $\widetilde{P}^{\otimes n}$ is free, and the modules $P_n$ exhibit a type of "Bott Periodicity" of period $4$: $P_{n+4} = Σ^8P_n$. These facts taken together allow one to analyze the module of indecomposables in $\widetilde{P}^{\otimes n}$, that is, to say something about the "$\mathcal{A}(1)$-hit Problem." Our study is essentially in two parts: First, we expound on the approach to the Hit Problem begun by William Singer, in which we compare images of Steenrod Squares to certain kernels of Squares. Using this approach, the author discovered a nontrivial element in bidegree $(5, 9)$ that is neither $\mathcal{A}(1)$-hit nor in $\mathrm{ker} Sq^1 + \mathrm{ker} Sq^3$. Such an element is extremely rare, but Bruner's result shows clearly why these elements exist and detects them in full generality. Second, we describe the graded $\mathbb{F}_2$-space of $\mathcal{A}(1)$-hit elements of $\widetilde{P}^{\otimes n}$ by determining its Hilbert series.
We explore a question related to the celebrated Erdős-Szekeres Theorem and develop a geometric approach to answer it. Our main object of study is the Erdős-Szekeres tableau, or EST, of a number sequence. An EST is the sequence of integral points whose coordinates record the length of the longest increasing and longest decreasing subsequence ending at each element of the sequence. We define the Order Poset of an EST in order to answer the question: What information about the sequence can be recovered by its EST?
In this note, we examine the right action of the Steenrod algebra $\mathcal{A}$ on the homology groups $H_*(BV_s, \F_2)$, where $V_s = \F_2^s$. We find a relationship between the intersection of kernels of $Sq^{2^i}$ and the intersection of images of $Sq^{2^{i+1}-1}$, which can be generalized to arbitrary right $\mathcal{A}$-modules. While it is easy to show that $\bigcap_{i=0}^{k} \mathrm{im}\,Sq^{2^{i+1}-1} \subseteq \bigcap_{i = 0}^k \mathrm{ker}\,Sq^{2^i}$ for any given $k \geq 0$, the reverse inclusion need not be true. We develop the machinery of homotopy systems and null subspaces in order to address the natural question of when the reverse inclusion can be expected. In the second half of the paper, we discuss some counter-examples to the reverse inclusion, for small values of $k$, that exist in $H_*(BV_s, \F_2)$.
The symmetric homology of a unital algebra $A$ over a commutative ground ring $k$ is defined using derived functors and the symmetric bar construction of Fiedorowicz. For a group ring $A = k[Γ]$, the symmetric homology is related to stable homotopy theory via $HS_*(k[Γ]) \cong H_*(ΩΩ^{\infty} S^{\infty}(BΓ); k)$. Two chain complexes that compute $HS_*(A)$ are constructed, both making use of a symmetric monoidal category $ΔS_+$ containing $ΔS$. Two spectral sequences are found that aid in computing symmetric homology. The second spectral sequence is defined in terms of a family of complexes, $Sym^{(p)}_*$. $Sym^{(p)}$ is isomorphic to the suspension of the cycle-free chessboard complex $Ω_{p+1}$ of Vrećica and Živaljević, and so recent results on the connectivity of $Ω_n$ imply finite-dimensionality of the symmetric homology groups of finite-dimensional algebras. Some results about the $kΣ_{p+1}$--module structure of $Sym^{(p)}$ are devloped. A partial resolution is found that allows computation of $HS_1(A)$ for finite-dimensional $A$ and some concrete computations are included.
We examine the dual of the so-called "hit problem", the latter being the problem of determining a minimal generating set for the cohomology of products of infinite projective spaces as module over the Steenrod Algebra $\mathcal{A}$ at the prime 2. The dual problem is to determine the set of $\mathcal {A}$-annihilated elements in homology. The set of $\mathcal{A}$-annihilateds has been shown by David Anick to be a free associative algebra. In this note we prove that, for each $k \geq 0$, the set of {\it $k$ partially $\mathcal{A}$-annihilateds}, the set of elements that are annihilated by $Sq^i$ for each $i\leq 2^k$, itself forms a free associative algebra.
A block cipher is intended to be computationally indistinguishable from a random permutation of appropriate domain and range. But what are the properties of a random permutation? By the aid of exponential and ordinary generating functions, we derive a series of collolaries of interest to the cryptographic community. These follow from the Strong Cycle Structure Theorem of permutations, and are useful in rendering rigorous two attacks on Keeloq, a block cipher in wide-spread use. These attacks formerly had heuristic approximations of their probability of success. Moreover, we delineate an attack against the (roughly) millionth-fold iteration of a random permutation. In particular, we create a distinguishing attack, whereby the iteration of a cipher a number of times equal to a particularly chosen highly-composite number is breakable, but merely one fewer round is considerably more secure. We then extend this to a key-recovery attack in a "Triple-DES" style construction, but using AES-256 and iterating the middle cipher (roughly) a million-fold. It is hoped that these results will showcase the utility of exponential and ordinary generating functions and will encourage their use in cryptanalytic research.