On exponential sums over primes in short intervals

Let Λ(n) be the von Mangoldt function, x real and y small compared with x. This paper gives a non-trivial estimate on the exponential sum over primes in short intervals for all α ∈ [0,1] whenever . This result is as good as what was previously derived from the Generalized Riemann Hypothesis.     

On sums of a prime and four prime squares in short intervals

In this paper, we are able to sharpen Hua's classical result by showing that each sufficiently large integer can be written as

     

Two results on powers of 2 in Waring-Goldbach problem

In this paper, it is proved that every sufficiently large odd integer is a sum of a prime, four cubes of primes and 106 powers of 2. What is more, every sufficiently large even integer is a sum of two squares of primes, four cubes of primes and 211 powers of 2.     

On a Waring-Goldbach-type problem for fourth powers

In this paper, we prove that every sufficiently large positive integer satisfying some necessary congruence conditions can be represented by the sum of a fourth power of integer and twelve fourth powers of prime numbers.     

On sums of squares of primes II

In this paper we continue our study, begun in G. Harman and A.V. Kumchev (2006) [10], of the exceptional set of integers, not restricted by elementary congruence conditions, which cannot be represented as sums of three or four squares of primes. We correct a serious oversight in our first paper, but make further progress on the exponential sums estimates needed, together with an embellishment of the previous sieve technique employed. This leads to an improvement in our bounds for the maximal size of the exceptional sets.     

Irregularities in the distributions of primes in function fields

We adapt the Maier matrix method to the polynomial ring Fq[t], and prove analogues of results of Maier [H. Maier, Primes in short intervals, Michigan Math. J. 32 (1985) 221-225] and Shiu [D.K.L. Shiu, Strings of congruent primes, J. London Math. Soc. 61 (2000) 359-373] concerning the distribution of primes in short intervals.     

The quadratic Waring-Goldbach problem

It is conjectured that Lagrange's theorem of four squares is true for prime variables, i.e. all positive integers n with are the sum of four squares of primes. In this paper, the size for the exceptional set in the above conjecture is reduced to .     

Sums of four cubes

An upper bound for the numberE(N) of numbers not exceedingN and not being the sum of four cubes is given; namelyE(N)N ^131/147+e.     

A note on Mertens' formula for arithmetic progressions

We study the Mertens product over primes in arithmetic progressions, and find a uniform version of previous results.     

Sums of cubes of primes in short intervals

In this paper, we are able to sharpen Hua??s result by proving that almost all integers satisfying some necessary congruence conditions can be represented as $$N=p_1^3+ \cdots+p_s^3 \quad \mbox{with } \biggl \vert p_j-\sqrt[3]{\frac {N}{s}}\biggr \vert \leqslant U, j=1,\ldots, s, $$ where p _j are primes and $U=N^{\frac{1}{3}-\delta_{s}+\varepsilon }$ with $\delta_{s}=\frac{s-4}{6s+72}$ , where s=5,6,7,8.     

A note on the Waring-Goldbach problem

The focus of this paper will be the extension of the Waring-Goldbach problem to all sufficiently large integers, without congruence restrictions. By reintroducing the effect of small primes, we are able to consider questions which more naturally resemble Waring's problem and the Goldbach conjecture. We extend the results of S.S. Pillai by considering the problem without the use of zero as an addend and we give a small improvement on the number of additional terms required.     

An explicit result of the sum of seven cubes

We prove that every integer ≥ exp(524) is a sum of seven non negative cubes.     

Sums and Differences of Two Cubic Polynomials

 When f(x) is a cubic polynomial with integral coefficients, we show that almost all integers represented as the sum or difference of two values of f(x), with , are thus represented essentially uniquely. (Received 18 January 1999; in revised form 17 May 1999)     

On the Exceptional Set of Goldbach’s Problem in Short Intervals

Denote by E[X,X+H] the set of even integers in [X,X+H] that are not a sum of two primes (i.e. that are not Goldbach numbers). Here we prove that there exists a (small) positive constant such that for we have .     

On the number of representations in the ternary Goldbach problem with one prime number in a given residue class

For

     

Sums of squares on real algebraic surfaces

Consider real polynomials g₁, . . . , g_r in n variables, and assume that the subset K = {g₁≥0, . . . , g_r≥0} of ℝⁿ is compact. We show that a polynomial f has a representation in which the s_e are sums of squares, if and only if the same is true in every localization of the polynomial ring by a maximal ideal. We apply this result to provide large and concrete families of cases in which dim (K) = 2 and every polynomial f with f|_K≥0 has a representation (*). Before, it was not known whether a single such example exists. Further geometric and arithmetic applications are given. Support by DFG travel grant KON 1823/2002 and by the European RAAG network HPRN-CT-2001-00271 is gratefully acknowledged. Part of this work was done while the author enjoyed a stay at MSRI Berkeley. He would like to thank the institute for the invitation and the very pleasant working conditions.     

Growing perfect cubes

An (n,a,b)-perfect double cube is a b×b×b sized n-ary periodic array containing all possible a×a×a sized n-ary array exactly once as subarray. A growing cube is an array whose c_j×c_j×c_j sized prefix is an (n_j,a,c_j)-perfect double cube for , where and n₁<n₂<?. We construct the smallest possible perfect double cube (a 256×256×256 sized 8-ary array) and growing cubes for any a.     

Squares of Primes and Powers of 2

 As an extension of the Linnik-Gallagher results on the “almost Goldbach” problem, we prove, among other things, that there exists a positive integer k ₀ such that every large even integer is a sum of four squares of primes and k ₀ powers of 2. (Received 7 September 1998; in revised form 3 May 1999)     

Short effective intervals containing primes

We prove that every interval ]x(1−Δ⁻¹),x] contains a prime number with Δ=28314000 and provided x?10726905041. The proof combines analytical, sieve and algorithmical methods.