On the number of even latin squares of even order
We recall the Alon-Tarsi conjecture on the number of even latin squares. We introduce a map which switches the parity of a latin square under certain requirements. An example is included.
math.CO↗
arXiv subjects
Carolin Hannusch
Publications and source records attributed to Carolin Hannusch.
Decoding algorithm for HL-codes and performance of the DHH-cryptosystem -- a candidate for post-quantum cryptography
We give a decoding algorithm for a class of error-correcting codes, which can be used in the DHH-cryptosystem, which is a candidate for post-quantum cryptography, since it is of McEliece type. Furthermore, we implement the encryption and decryption algorithms for this cryptosystem and investigate its performance.
cs.CR↗
Neighborhoods of binary self-dual codes
In this paper, we introduce and investigate the neighborhood of binary self-dual codes. We prove that there is no better Type I code than the best Type II code of the same length. Further, we give some new necessary conditions for the existence of a singly-even $(56,28,12)$-code and a doubly-even $(72,36,16)$-code.
cs.IT↗
The search of Type I codes
A self-dual binary linear code is called Type I code if it has singly-even codewords, i.e.~it has codewords with weight divisible by $2.$ The purpose of this paper is to investigate interesting properties of Type I codes of different lengths. Further, we build up a computer-based code-searching program based on our knowledge about Type I codes. Some computation results achieved by this program are given.
cs.IT↗
Rotation on the digital plane
Let $A_φ$ denote the matrix of rotation with angle $φ$ of the Euclidean plane, FLOOR the function, which rounds a real point to the nearest lattice point down on the left and ROUND the function for rounding off a vector to the nearest node of the lattice. We prove under the natural assumption $φ\not= k\fracπ{2}$ that the functions $FLOOR \circ A_φ$ and $ROUND \circ A_φ$ are neither surjective nor injective. More precisely we prove lower and upper estimates for the size of the sets of lattice points, which are the image of two lattice points as well as of lattice points, which have no preimages. It turns out that the density of that sets are positive except when $\sin φ\not= \pm \cos φ+ r, r\in \mathbb{Q}$.
math.NT↗
Explicit bases of the Riemann-Roch spaces on divisors on hyperelliptic curves
For an (imaginary) hyperelliptic curve $\mathcal{H}$ of genus $g$, we determine a basis of the Riemann-Roch space $\mathcal{L}(D)$, where $D$ is a divisor with positive degree $n$, linearly equivalent to $P_1+\cdots+ P_j+(n-j)Ω$, with $0 \le j \le g$, where $Ω$ is a Weierstrass point, taken as the point at infinity. As an application, we determine a generator matrix of a Goppa code for $j=g=3$ and $n=4.$
math.AG↗
The largest character degrees of the symmetric and alternating groups
We show that the largest character degree of an alternating group $A_n$ with $n\geq 5$ can be bounded in terms of smaller degrees in the sense that \[ b(A_n)^2<\sum_{ψ\in\textrm{Irr}(A_n),\,ψ(1)< b(A_n)}ψ(1)^2, \] where $\textrm{Irr}(A_n)$ and $b(A_n)$ respectively denote the set of irreducible complex characters of $A_n$ and the largest degree of a character in $\textrm{Irr}(A_n)$. This confirms a prediction of I. M. Isaacs for the alternating groups and answers a question of M. Larsen, G. Malle, and P. H. Tiep.
math.GR↗