The sovability of norm, bilinear and quadratic equations over finite fields via spectra of graphs

We study the finite field Fourier restriction/extension problem for spheres in even dimensions d ≥ 4. We prove that the L p → L 4 extension estimate for spheres of non-zero radii holds for 4d 3d−2 ≤ p ≤ ∞. Our result is sharp and improves the L (12d−8)/(9d−12)+ε → L 4 extension result for all ε > 0 due to the first and second listed authors [7]. The key new ingredient is improved additive energy estimates for subsets of spheres in even dimensions. In particular, our additive energy estimate improves and extends Rudnev's recent work [15] in four dimensions to higher even dimensions.As the most interesting result of this paper, we prove that if −1 is not a square number of F * q and the dimension d is 4k + 2 for some k ∈ N, then the L 2 → L (2d+4)/d extension estimate for spheres of zero radius holds. This result is also sharp and provides us of an interesting fact that the L 2 → L r extension estimate for zero spheres with specific assumptions is much better than the Stein-Tomas result which can not be improved in general for cones or zero spheres in even dimensions.2010 Mathematics Subject Classification. 52C10, 42B05, 11T23 .

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“…Several more interesting results in this direction have been given by Hegyvári [121,122] and Vinh [198,201,205,206].…”

Section: Theorem 312 For Any Two Setsmentioning

confidence: 96%

“…Furthermore, Schoen & Shkredov [167] have successfully used a "cubic" generalization of the energy. We also have had to leave out such exciting areas of additive combinatorics in finite fields as • the Erdős distance problem [83,94,117,130,132,144,145] as well as its modification in some other settings (distinct volumes, configurations, and so on defined by arbitrary sets in F n q ) and metrics [14,64,142,195,200,202,203,205]; • the Kakeya problem and other related problems about the directions defined by arbitrary sets in vector spaces over a finite field, see [84-86, 88, 128, 131, 151]; • estimating the size of the sets in a finite field that avoid arithmetic or geometric progressions, sum sets and similar linear and non-linear relations; in particular these results include finite field analogues of the Roth and Szemerédi theorems, see [1,6,8,12,77,81,112,113,153,154,158,181]; • estimating the size of the sets in vector spaces over a finite field that define only some restrictive geometric configurations such as integral distances, acute angles, and pairwise orthogonal systems, see [75,133,134,183,194,204]; • distribution of the values of determinants and permanents of matrices with entries from general sets, see [74,196,197]; and several others.…”

Section: Introductionmentioning

confidence: 99%