We introduce invariants of graphs embedded in S3 which are related to the Wu invariant and the Simon invariant. Then we use our invariants to prove that certain graphs are intrinsically chiral, and to obtain lower bounds for the minimal crossing number of particular embeddings of graphs in S3.

In this paper we consider the probability distribution function of a Gibbs measure supported on a self-conformal set given by an iterated function system (devil's staircase) applied to a compact subset of ${\mathbb R}$. We use thermodynamic multifractal formalism to calculate the Hausdorff dimension of the sets Sα0, Sα∞ and Sα, the set of points at which this function has, respectively, Hölder derivative 0, ∞ or no derivative in the general sense. This extends recent work by Darst, Dekking, Falconer, Kesseböhmer and Stratmann, and Yao, Zhang and Li by considering arbitrary such Gibbs measures given by a potential function independent of the geometric potential.

In this paper we study Ulrich ideals of and Ulrich modules over Cohen--Macaulay local rings from various points of view. We determine the structure of minimal free resolutions of Ulrich modules and their associated graded modules, and classify Ulrich ideals of numerical semigroup rings and rings of finite CM-representation type.

In this short paper, we use Robert Bruner's $\cal{A}$(1)-resolution of $P = {\mathbb{F}_2[t]$ to shed light on the Hit Problem. In particular, the reduced syzygies Pn 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 Pn in $\widetilde{P}^{\otimes n}$ is free, and the modules Pn exhibit a type of “Bott periodicity” of period 4: Pn+4 = Σ8Pn. These facts taken together allow one to analyse the module of indecomposables in $\widetilde{P}^{\otimes n}$, that is, to say something about the “$\cal{A}$(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 $\cal{A}$(1)-hit nor in kerSq1 + kerSq3. 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 $\cal{A}$(1)-hit elements of $\widetilde{P}^{\otimes n}$ by determining its Hilbert series.

We give a lower bound on the Loewy length of a p-block of a finite group in terms of its defect. We then discuss blocks with small Loewy length. Since blocks with Loewy length at most 3 are known, we focus on blocks of Loewy length 4 and provide a relatively short list of possible defect groups. It turns out that p-solvable groups can only admit blocks of Loewy length 4 if p=2. However, we find (principal) blocks of simple groups with Loewy length 4 and defect 1 for all p ≡ 1 (mod 3). We also consider sporadic, symmetric and simple groups of Lie type in defining characteristic. Finally, we give stronger conditions on the Loewy length of a block with cyclic defect group in terms of its Brauer tree.

We study the existence of semi-classical bound states of the nonlinear Schrödinger equation

\begin{linenomath}$$ -\varepsilon^2\Delta u+V(x)u=f(u),\quad x\in {\bf R}^N,$$\end{linenomath}

We present a proof of the formula, due to Mellit and Brunault, which evaluates an integral of the regulator of two modular units to the value of the L-series of a modular form of weight 2 at s=2. Applications of the formula to computing Mahler measures are discussed.

In this paper we prove, under a technical assumption, the so-called “Möbius–Wall” congruences between abelian p-adic L-functions of CM elliptic curves. These congruences are the analogue of those shown by Ritter and Weiss for the Tate motive, and offer strong evidences in favor of the existence of non-abelian p-adic L-functions for CM elliptic curves.

Combining Freiman's theorem with Balog–Szemerédi–Gowers theorem one can show that if an additive set has large additive energy, then a large piece of the set is contained in a generalized arithmetic progression of small rank and size. In this paper, we prove the above statement with the optimal bound for the rank of the progression. The proof strategy involves studying upper bounds for additive energy of subsets of ${\mathbb{R}^d$ and ${\mathbb{Z}^d$.

In this paper, we prove that the full automorphism group of the ${\mathbb Z}_2$-orbifold of the Barnes–Wall lattice vertex operator algebra of central charge 32 has the shape 227.E6(2). In order to identify the group structure, we introduce a graph structure on the Griess algebra and show that it is a rank 3 graph associated to E6(2).

For a handlebody H, we define two graphs, the augmented disk graph $\mathcal{ADG}(H)$ and the truncated augmented disk graph $\mathcal{TADG}(H)$, and we show they are hyperbolic in the sense of Gromov. In the process, we show they are quasi-isometric to two other disk graphs defined by U. Hamenstädt, the super conducting disk graph $\mathcal{SDG}(H)$ and the electrified disk graph $\mathcal{EDG}(H)$ respectively. So we reprove two theorems of Hamenstädt [12].

Our approach uses techniques from Masur–Schleimer's study on the hyperbolicity of the disk graph $\mathcal{DG}(H)$ [21].