A two-step problem of hedging a European call option under a random duration of transactions

We improve previous sum–product estimates in ?; namely, we prove the inequality max{|A + A|, |AA|} ? |A|^4/3+c, where c is any number less than 5/9813. New lower bounds for sums of sets with small product set are found. We also obtain results on the additive and multiplicative energies; in particular, we improve a result of Balog and Wooley.     

A graph theoretic upper bound on the permanent of a nonnegative integer matrix. I

Let A be a fully indecomposable n×n matrix with nonnegative integer entries. Then the permanent of A is bounded above by 1+min{Π(c_i?1), Π(r_i?1)}, where c_i and r_i are the column and row sums of A. The inequality results from a bound on the number of disjoint cycle unions in an associated multigraph. This bound can improve via contractions.     

Representing matrices

Let A be a nonnegative real matrix whose column set is countable. We give a necessary and sufficient condition on A for the existence of a nonnegative matrix B, B ? A, with column sums equal to prescribed numbers, and row sums not greater than prescribed numbers. This is a generalization of a result of Damerell and Milner, who solved the problem for (0, 1) matrices.     

Some new results on subset sums

Let n be a large integer and A be a subset of [n]={1,…,n}. The set SA is the collection of the subset sums of A. In this note, we discuss new results (and proofs) on few well-known problems concerning SA. In particular, we improve an estimate of Alon and Erd?s concerning monochromatic representations.     

On a problem of Sierpiński,Ⅱ

For any integer s≥ 2, let μsbe the least integer so that every integer l μs is the sum of exactly s integers which are pairwise relatively prime. In 1964, Sierpi′nski asked for the determination of μs. Let pibe the i-th prime and let μs= p2 + p3 + + ps+1+ cs. Recently, the authors solved this problem. In particular,we have(1) cs=-2 if and only if s = 2;(2) the set of integers s with cs= 1100 has asymptotic density one;(3) cs∈ A for all s ≥ 3, where A is an explicit set with A ■[2, 1100] and |A| = 125. In this paper, we prove that,(1) for every a ∈ A, there exists an index s with cs= a;(2) under Dickson's conjecture, for every a ∈ A,there are infinitely many s with cs= a. We also point out that recent progress on small gaps between primes can be applied to this problem.     

Difference sets and shifted primes

We show that if A is a subset of {1, …, n} which has no pair of elements whose difference is equal to p ? 1 with p a prime number, then the size of A is O(n(log log n)^{?c(log log log log log n)}) for some absolute c > 0.     

Dedekind sums in function fields

Okada (J Number Theory, 130:1750–1762, 2010) introduced Dedekind sums associated to a certain A-lattice, and established the reciprocity law. In this paper, we introduce Dedekind sums for arbitrary A-lattice and establish the reciprocity law for them. We next introduce higher dimensional Dedekind sums for any A-lattice. These Dedekind sums are analogues of Zagier’s higher dimensional Dedekind sums. We discuss the reciprocity law, rationality and characterization of these sums.     

A problem of D.H. Lehmer and its mean square value formula

Let q be an odd positive integer and let a be an integer coprime to q. For each integer b coprime to q with 1?b<q, there is a unique integer c coprime to q with 1?c<q such that . Let N(a,q) denote the number of solutions of the congruence equation with 1?b,c<q such that b,c are of opposite parity. The main purpose of this paper is to use the properties of Dedekind sums, the properties of Cochrane sums and the mean value theorem of Dirichlet L-functions to study the asymptotic property of the mean square value , and give a sharp asymptotic formula.     

Cone Dependence—A Basic Combinatorial Concept

We call A ? $ \mathbb{E} $ ⁿ cone independent of B ? $ \mathbb{E} $ ⁿ , the euclidean n-space, if no a = (a ₁,..., a _n ) ∈ A equals a linear combination of B \ {a} with non-negative coefficients. If A is cone independent of A we call A a cone independent set. We begin the analysis of this concept for the sets P(n) = {A ? {0, 1} ⁿ ? $ \mathbb{E} $ ⁿ : A is cone independent} and their maximal cardinalities c(n) ? max{|A| : A ∈ P(n)}. We show that lim _{n → ∞} $ \frac{{c\left( n \right)}}{{2^n }} $ > $\frac{1}{2}$ , but can't decide whether the limit equals 1. Furthermore, for integers 1 < k < ? ≤ n we prove first results about c _n (k, ?) ? max{|A| : A ∈ P _n (k, ?)}, where P _n (k, ?) = {A : A ? V ⁿ _k and V ⁿ _? is cone independent of A} and V ⁿ _k equals the set of binary sequences of length n and Hamming weight k. Finding c _n (k, ?) is in general a very hard problem with relations to finding Turan numbers.     

Representation of tripotents and representations via tripotents

Let A be an algebra. An element A∈A is called tripotent if A³=A. We study the questions: if both A and B are tripotents, then: Under what conditions are A+B and AB tripotent? Under what conditions do A and B commute? We extend the partial order from the Hilbert space idempotents to the set of all tripotents and show that every normal tripotent is self-adjoint. For A=M_n(C) we describe the set of all finite sums of tripotents, the convex hull of tripotents and the set of all tripotents averages. We also give the new proof of rational trace matrix representations by Choi and Wu [2].     

Short sums with a noninteger power of a natural number

We establish a nontrivial estimate for a short trigonometric sum of the form Ω _{x ? y < n ≤ x} e(α[n ^c ]), where u ≥ √2cx ?^6A , A ≥ 1 is a fixed number, ? = ln x and c is a noninteger satisfying the conditions $$1 < c \leqslant \log _2 L - \log _2 \ln L^{6A} , \left\| c \right\| \geqslant \left( {2^{\left[ c \right] + 1} - 1} \right)\left( {A + 1} \right)L^{ - 1} \ln L.$$      

Some results on Korenblum's maximum principle

Let Ap(D) (1?p<∞) be the Bergman space over the open unit disk D in the complex plane. For p?1, let cp be the largest value of c for which Korenblum's maximum principle holds. In this paper we obtain a new lower bound on cp: cp?0.23917. We also improve the lower bound on c₂ up to 0.28185.     

Bounds for norms of the matrix inverse and the smallest singular value

In the first part, we obtain two easily calculable lower bounds for ‖A^-1‖, where ‖·‖ is an arbitrary matrix norm, in the case when A is an M-matrix, using first row sums and then column sums. Using those results, we obtain the characterization of M-matrices whose inverses are stochastic matrices. With different approach, we give another easily calculable lower bounds for ‖A^-1‖_∞ and ‖A^-1‖₁ in the case when A is an M-matrix. In the second part, using the results from the first part, we obtain our main result, an easily calculable upper bound for ‖A^-1‖₁ in the case when A is an SDD matrix, thus improving the known bound. All mentioned norm bounds can be used for bounding the smallest singular value of a matrix.     

Intervals and tests for weighted sum of percentiles θ(p) and θ(1−p) for symmetrical populations

Available is a random sample from a distribution that is continuous, symmetrical, and reasonably well-behaved. Approximate one-sided and two-sided confidence intervals (provide tests) are developed forAθ(p)+Bθ(1?p), where θ(p) is the population 100p percentile, 1/2≦p<1, andA, B can be any positive or negative numbers. The interquantile and other ranges are special cases. Asymptotically, a confidence coefficient value is precisely determined. The statistics used are weighted sums (with weightsA andB) of two percentage points of the sample. Many comparisons of population percentiles can be made through suitable choice ofp, A, andB.     

Weighted Bounds for Variational Walsh–Fourier Series

For 1<p<?? and a weight w??A _p and a function in L ^p ([0,1],w) we show that variational sums with sufficiently large exponents of its Walsh?CFourier series are bounded in L ^p (w). This strengthens a result of Hunt?CYoung and is a weighted extension of a variation norm Carleson theorem of Oberlin?CSeeger?CTao?CThiele?CWright. The proof uses phase plane analysis and a weighted extension of a variational inequality of Lépingle.     

Difference Sets and Positive Exponential Sums I. General Properties

We describe general connections between intersective properties of sets in Abelian groups and positive exponential sums. In particular, given a set A the maximal size of a set whose difference set avoids A will be related to positive exponential sums using frequencies from A.     

Operator Spaces Containing c 0 OR l∞

Let E, F be either Fréchet or complete DF-spaces and let A(E, F) ? B(E, F) be spaces of operators. Under some quite general assumptions we show that: (i) A(E, F) contains a copy of c ₀ if and only if it contains a copy of l _∞; (ii) if c ₀ ? A(E, F), then A(E, F) is complemented in B(E, F) if and only if A(E, F) = B(E, F); (iii) if E or F has an unconditional basis and A(E, F) ≠ L(E, F), then A(E, F) ? c ₀. The above results cover cases of many clssical operator spaces A. We show also that EεF contains l _∞ if and only if E or F contains l _∞.     

Singular value inequalities for matrix sums and minors

This paper gives new proofs for certain inequalities previously established by the author involving sums of singular values of matrices A, B, C = A + B, and also sums of singular values of A, B, and C when A, B are complementary submatrices of C. Some new facts concerning these inequalities are also included.     

On Lehmer’s problem and Dedekind sums

Let p be an odd prime and c a fixed integer with (c, p) = 1. For each integer a with 1 ≤ a ≤ p ? 1, it is clear that there exists one and only one b with 0 ? b ? p ? 1 such that ab ≡ c (mod p). Let N(c, p) denote the number of all solutions of the congruence equation ab ≡ c (mod p) for 1 ? a, b ? p?1 in which a and \(\overline b \) are of opposite parity, where \(\overline b \) is defined by the congruence equation b\(\overline b \) ≡ 1 (mod p). The main purpose of this paper is to use the properties of Dedekind sums and the mean value theorem for Dirichlet L-functions to study the hybrid mean value problem involving N(c, p)?½φ(p) and the Dedekind sums S(c, p), and to establish a sharp asymptotic formula for it.     

On the reciprocal sum of a sum-free sequence

Let A = {1≤a1相似文献