Proof of the impossibility of the fermat equation Xp + Yp = Zp for special values of p and of the more general equation bXn + cYn = dZn

This paper continues the search to determine for what exponents n Fermat's Last Theorem is true. The main theorem and Corollary 1 consider the set of prime exponents p for which mp + 1 is prime for certain even integers m and prove the truth of FLT in Case 1 for such primes p. The remaining theorems prove the inequality of the more general Fermat equation bXⁿ + cYⁿ = dZⁿ.     

Zeta function of the projective curveaY 21 =bX 21 +cZ 21 over a class of finite fields, for odd primesl

Letp andl be rational primes such thatl is odd and the order ofp modulol is even. For such primesp andl, and fore = l, 2l, we consider the non-singular projective curvesaY ²¹ =bX ²¹ +cZ ²¹ defined over finite fields F_q such thatq = p ^α? l(mode).We see that the Fermat curves correspond precisely to those curves among each class (fore = l, 2l), that are maximal or minimal over F_q. We observe that each Fermat prime gives rise to explicit maximal and minimal curves over finite fields of characteristic 2. Fore = 2l, we explicitly determine the ζ -function(s) for this class of curves, over F_q, as rational functions in the variablet, for distinct cases ofa, b, andc, in F _q ^* . Theζ-function in each case is seen to satisfy the Weil conjectures (now theorems) for this concrete class of curves. Fore = l, 2l, we determine the class numbers for the function fields associated to each class of curves over F_q. As a consequence, when the field of definition of the curve(s) is fixed, this provides concrete information on the growth of class numbers for constant field extensions of the function field(s) of the curve(s).     

A note on factors of generalized Fermat numbers

Some properties of the factors of both standard Fermat numbers, F_m = 2^2m + 1, and generalized Fermat numbers, F_m(a, b) = a^2m + b^2m, are reported. The properties are mainly related to the presence of common prime factors. Several anomalies in the distribution of factors are also analyzed.     

On the Convergence of Series of Reciprocals of Primes Related to the Fermat Numbers

We examine densities of several sets connected with the Fermat numbers F_m=2^2m+1. In particular, we prove that the series of reciprocals of all prime divisors of Fermat numbers is convergent. We also show that the series of reciprocals of elite primes is convergent.     

Enumeration of finite topologies

Let T₀(n) be the number of marked topologies satisfying the separation axiom T₀ that can be imposed on a finite set of n elements. In this paper the formula $$T_0 \left( n \right) = \Sigma \frac{{n!}}{{p_1 !...p_m !}}V\left( {p_1 , ..., p_m } \right)$$ is obtained, where the summation extends over all ordered sets of natural numbers (p₁, ..., p_m) such that p₁+...+p_m=n, and V(p₁, ..., p_m) denotes the number of matrices σ=(σ_ij) of ordern with the following properties: 1) each of the entries σ_ij is either 0 or 1, and if σ_ij=1 andσ_ij=1, then σ_ij=1;2) if the matrix σ is partitioned into blocks of sizes p_ixp_j, then all blocks under the main diagonal are zero, all diagonal blocks are identity matrices, and in each column of any block situated above the main diagonal at least one entry is 1. Some properties of the values V(p₁, ..., p_m)are obtained; in particular, it is shown that all these values are odd. Formulas are obtained for V(P₁, ..., p_m) corresponding to the simplest sets (p₁, ..., P_m) needed to calculate T₀(n) for n?8 (without using a computer).     

Gradient estimates for higher order elliptic equations on nonsmooth domains

We establish optimal gradient estimates in Orlicz space for a nonhomogeneous elliptic equation of higher order with discontinuous coefficients on a nonsmooth domain. Our assumption is that for each point and for each sufficiently small scale the coefficients have small mean oscillation and the boundary of the domain is sufficiently close to a hyperplane. As a consequence we prove the classical Wm,p, m=1,2,…, 1<p<∞, estimates for such a higher order equation. Our results easily extend to higher order elliptic and parabolic systems.     

The fourth power of the Fermat quotient

Let p be an odd prime and qp(a)=(ap−1−1)/p be the Fermat quotient with base a, p?a. The main purpose of this paper is to investigate the fourth power problem of qp(2) and deduce an explicit formula represented by a linear combination of Mirimanoff polynomial values.     

On the boundedness of generalized solutions of higher-order nonlinear elliptic equations with data from an Orlicz–Zygmund class

In the present paper, a 2mth-order quasilinear divergence equation is considered under the condition that its coefficients satisfy the Carathéodory condition and the standard conditions of growth and coercivity in the Sobolev space W^m,p(Ω), Ω ? Rⁿ, p > 1. It is proved that an arbitrary generalized (in the sense of distributions) solution u ∈ W₀^m,p (Ω) of this equation is bounded if m ≥ 2, n = mp, and the right-hand side of this equation belongs to the Orlicz–Zygmund space L(log L)^n?1(Ω).     

Soliton solutions for (2 + 1)-dimensional and (3 + 1)-dimensional K(m, n) equations

We consider the nonlinear dispersive K(m,n) equation with the generalized evolution term and derive analytical expressions for some conserved quantities. By using a solitary wave ansatz in the form of sech^p function, we obtain exact bright soliton solutions for (2 + 1)-dimensional and (3 + 1)-dimensional K(m,n) equations with the generalized evolution terms. The results are then generalized to multi-dimensional K(m,n) equations in the presence of the generalized evolution term. An extended form of the K(m,n) equation with perturbation term is investigated. Exact bright soliton solution for the proposed K(m,n) equation having higher-order nonlinear term is determined. The physical parameters in the soliton solutions are obtained as function of the dependent model coefficients.     

PBIB designs with m associate classes induced by full rank matrices modulo pm

This paper presents series of PBIB designs with m associate classes in which the treatment set is a subset of the Z(p^m)-module of n × 1 vectors over the ring of integers modulo p^m, p any prime. The association scheme of this series of designs is determined by the Fuller canonical form under row equivalence of n × 2 matrices [a,b] for vectors a and b in the treatment set. The blocking procedure utilizes full rank s × n matrices over Z(p^m), 1 ? s ? n ? 2, n ? 3. For m = 2, n = 3, s =1 and for each prime p, each PBIB is regular divisible and yields a finite proper uniform projective Hjelmslev plane with parameters j = p and k = p(p + 1).     

Multiplicative character sums of Fermat quotients and pseudorandom sequences

We prove a bound on sums of products of multiplicative characters of shifted Fermat quotients modulo p. From this bound we derive results on the pseudorandomness of sequences of modular discrete logarithms of Fermat quotients modulo p: bounds on the well-distribution measure, the correlation measure of order ?, and the linear complexity.     

On the Second Parameter of an (<Emphasis Type="Italic">m</Emphasis>, <Emphasis Type="Italic">p</Emphasis>)-Isometry

A bounded linear operator T on a Banach space X is called an (m, p)-isometry if it satisfies the equation \({\sum_{k=0}^{m}(-1)^{k} {m \choose k}\|T^{k}x\|^{p}=0}\) , for all \({x \in X}\) . In this paper we study the structure which underlies the second parameter of (m, p)-isometric operators. We concentrate on determining when an (m, p)-isometry is a (μ, q)-isometry for some pair (μ, q). We also extend the definition of (m, p)-isometry, to include p = ∞ and study basic properties of these (m, ∞)-isometries.     

Hamilton Cycle Rich 2-Factorization of Complete Equipartite Graphs-II

For any given two 2-factors G and H of a complete p-partite graph K(m, p), with m vertices in each partite set, we prove the existence of a 2-factorization of K(m, p), in which one 2-factor is isomorphic to G, another 2-factor is isomorphic to H and the remaining 2-factors are hamilton cycles. Further, we prove the corresponding result for K(m, p) ? I, where I is a 1-factor of K(m, p), when K(m, p) is an odd regular graph. In fact our results together with the results of McCauley and Rodger settled the problem of 2-factorization of K(m, p), when two of the 2-factors are isomorphic to the given two 2-factors and the remaining 2-factors are hamilton cycles except for (m, p)?=?(m, 2).     

On a kind of generalized Lehmer problem

For 1 ? c ? p ? 1, let E ₁,E ₂, …,E _m be fixed numbers of the set {0, 1}, and let a ₁, a ₂, …, a _m (1 ? a _i ? p, i = 1, 2, …,m) be of opposite parity with E ₁,E ₂, …,E _m respectively such that a ₁ a ₂…a _m ≡ c (mod p). Let $$N(c,m,p) = {1 \over {{2^{m - 1}}}}\mathop {\sum\limits_{{a_1} = 1}^{p - 1} {\sum\limits_{{a_2} = 1}^{p - 1} \ldots } }\limits_{{a_1}{a_2} \ldots \equiv c{\rm{ (}}\bmod {\rm{ }}p)} \sum\limits_{{a_m} = 1}^{p - 1} {(1 - {{( - 1)}^{{a_1} + {E_1}}})(1 - {{( - 1)}^{{a_2} + {E_2}}}) \ldots } (1 - {( - 1)^{{a_m} + {E_m}}}).$$ We are interested in the mean value of the sums $$\sum\limits_{c = 1}^{p - 1} {{E^2}} (c,m,p),$$ where E(c, m, p) = N(c,m, p)?((p ? 1) ^m?1)/(2 ^m?1) for the odd prime p and any integers m ? 2. When m = 2, c = 1, it is the Lehmer problem. In this paper, we generalize the Lehmer problem and use analytic method to give an interesting asymptotic formula of the generalized Lehmer problem.     

Quadratic Hermite-Padé approximation to the exponential function

Approximation to exp of the form wherep _m,q _m, andr _m are polynomials of degree at mostm andp _m has lead coefficient 1 is considered. Exact asymptotics and explicit formulas are obtained for the sequences {? _m}, {p _m}, {q _m}, and {r _m}. It is observed that the above sequences all satisfy the simple four-term recursion: $$\begin{array}{*{20}c} {T_{m + 3} = \frac{1}{{3m + 4}}[( - 6m - 14)z^3 T_m } \\ { + (9m + 15)(z^2 + (3m + 4)(3m + 7))T_{m + 1} + 3zT_{m + 2} ].} \\ \end{array} $$ It is also observed that these generalized Padé-type approximations can be used to asymptotically minimize expressions of the above form on the unit disk.     

Enumeration of power sums modulo a prime

We consider, for odd primes p, the function N(p, m, α) which equals the number of subsets S?{1,…,p ? 1} with the property that Σ_∞∈Sx^m ≡ α (mod p). We obtain a closed form expression for N(p, m, α). We give simple explicit formulas for N(p, 2, α) (which in some cases involve class numbers and fundamental units), and show that for a fixed m, the difference between N(p, m, α) and its average value p^?12^p?1 is of the order of $\text{exp}\text{(p}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$ or less. Finally, we obtain the curious result that if p ? 1 does not divide m, then N(p, m, 0) > N(p, m, α) for all α ? 0 (mod p).     

The generalised Fermat equation x 2 + y 3 = z 15

We determine the set of primitive integral solutions to the generalised Fermat equation x ² + y ³ = z ¹⁵. As expected, the only solutions are the trivial ones with xyz = 0 and the non-trivial one (x, y, z) = (± 3, ?2, 1).     

Partitions and sums of (m,p, c)-sets

The (m, p, c)-sets characterize those sets which contain solutions to every partition-regular system of homogeneous linear equations. We show that if N is partitioned into finitely many classes there is one class and for each (m, p, c) ϵ N × N × N, an (m, p, c) set B(m, p, c) such that all finite sums choosing at most one term from each B(m, p, c) lie in the given class.     

Elliptic operators with general Wentzell boundary conditions,analytic semigroups and the angle concavity theorem

We prove a very general form of the Angle Concavity Theorem, which says that if (T (t)) defines a one parameter semigroup acting over various L^p spaces (over a fixed measure space), which is analytic in a sector of opening angle θ_p, then the maximal choice for θ_p is a concave function of 1 – 1/p. This and related results are applied to give improved estimates on the optimal L^p angle of ellipticity for a parabolic equation of the form ?u /?t = Au, where A is a uniformly elliptic second order partial differential operator with Wentzell or dynamic boundary conditions. Similar results are obtained for the higher order equation ?u /?t = (–1)^{m +l}A^mu, for all positive integers m.