Abel, Ulrich; Leviatan, Dany An extension of Raşa’s conjecture to \(q\)-monotone functions. (English) Zbl 1461.26008 Result. Math. 75, No. 4, Paper No. 180, 13 p. (2020); correction ibid. 78, No. 4, Paper No. 122, 3 p. (2023). Reviewer: D. K. Ugulava (Tbilisi) MSC: 26D05 39B62 41A17 41A36 PDFBibTeX XMLCite \textit{U. Abel} and \textit{D. Leviatan}, Result. Math. 75, No. 4, Paper No. 180, 13 p. (2020; Zbl 1461.26008) Full Text: DOI
Gibali, Aviv; Jolaoso, Lateef Olakunle; Mewomo, Oluwatosin Temitope; Taiwo, Adeolu Fast and simple Bregman projection methods for solving variational inequalities and related problems in Banach spaces. (English) Zbl 07271472 Result. Math. 75, No. 4, Paper No. 179, 35 p. (2020). MSC: 47H10 47J25 47N10 65J15 90C33 PDFBibTeX XMLCite \textit{A. Gibali} et al., Result. Math. 75, No. 4, Paper No. 179, 35 p. (2020; Zbl 07271472) Full Text: DOI
Shi, Yong-Guo Single-valley-extended solutions with platforms of FKS equation. (English) Zbl 1457.39014 Result. Math. 75, No. 4, Paper No. 178, 9 p. (2020). Reviewer: Mihály Bessenyei (Debrecen) MSC: 39B12 39B22 37E05 PDFBibTeX XMLCite \textit{Y.-G. Shi}, Result. Math. 75, No. 4, Paper No. 178, 9 p. (2020; Zbl 1457.39014) Full Text: DOI arXiv
Frerick, Leonhard; Loosveldt, Laurent; Wengenroth, Jochen Continuously differentiable functions on compact sets. (English) Zbl 1462.46024 Result. Math. 75, No. 4, Paper No. 177, 18 p. (2020). Reviewer: Jan-David Hardtke (Leipzig) MSC: 46E15 PDFBibTeX XMLCite \textit{L. Frerick} et al., Result. Math. 75, No. 4, Paper No. 177, 18 p. (2020; Zbl 1462.46024) Full Text: DOI arXiv Backlinks: MO
Lü, Weiran; Zhang, Xiaoxue On the periodicity of entire functions. (English) Zbl 1451.30057 Result. Math. 75, No. 4, Paper No. 176, 12 p. (2020). MSC: 30D15 30D35 PDFBibTeX XMLCite \textit{W. Lü} and \textit{X. Zhang}, Result. Math. 75, No. 4, Paper No. 176, 12 p. (2020; Zbl 1451.30057) Full Text: DOI
Chang, Jui-En Self-similar solutions to the inverse mean curvature flow in \(\mathbb{R}^2\). (English) Zbl 1454.53078 Result. Math. 75, No. 4, Paper No. 175, 18 p. (2020). Reviewer: Ergin Bayram (Samsun) MSC: 53E10 53A04 PDFBibTeX XMLCite \textit{J.-E. Chang}, Result. Math. 75, No. 4, Paper No. 175, 18 p. (2020; Zbl 1454.53078) Full Text: DOI arXiv
Behera, Ratikanta; Maharana, Gayatri; Sahoo, Jajati Keshari Further results on weighted core-EP inverse of matrices. (English) Zbl 1453.15002 Result. Math. 75, No. 4, Paper No. 174, 20 p. (2020). Reviewer: Mohammad Sal Moslehian (Mashhad) MSC: 15A09 15A10 15A24 15A30 PDFBibTeX XMLCite \textit{R. Behera} et al., Result. Math. 75, No. 4, Paper No. 174, 20 p. (2020; Zbl 1453.15002) Full Text: DOI arXiv
Li, An-Min; Li, Xingxiao; Zhang, Di On the mean curvature flow of submanifolds in the standard Gaussian space. (English) Zbl 1453.53083 Result. Math. 75, No. 4, Paper No. 173, 38 p. (2020). MSC: 53E10 53B20 PDFBibTeX XMLCite \textit{A.-M. Li} et al., Result. Math. 75, No. 4, Paper No. 173, 38 p. (2020; Zbl 1453.53083) Full Text: DOI arXiv
Carrillo Rouse, Paulo; So, Bing Kwan K-theory and index theory for some boundary groupoids. (English) Zbl 1453.58006 Result. Math. 75, No. 4, Paper No. 172, 19 p. (2020). Reviewer: Iakovos Androulidakis (Athína) MSC: 58J20 58H05 46L80 PDFBibTeX XMLCite \textit{P. Carrillo Rouse} and \textit{B. K. So}, Result. Math. 75, No. 4, Paper No. 172, 19 p. (2020; Zbl 1453.58006) Full Text: DOI
Balcerzak, Marek; Leonetti, Paolo The Baire category of subsequences and permutations which preserve limit points. (English) Zbl 1461.40005 Result. Math. 75, No. 4, Paper No. 171, 13 p. (2020). Reviewer: Ljubiša D. Kočinac (Niš) MSC: 40A35 11B05 54A20 PDFBibTeX XMLCite \textit{M. Balcerzak} and \textit{P. Leonetti}, Result. Math. 75, No. 4, Paper No. 171, 13 p. (2020; Zbl 1461.40005) Full Text: DOI arXiv
Gröger, Detlef Construction of locally compact near-fields from \(\mathfrak{p}\)-adic division algebras. (English) Zbl 1480.12008 Result. Math. 75, No. 4, Paper No. 170, 9 p. (2020). Reviewer: Norbert Knarr (Stuttgart) MSC: 12K05 11S45 PDFBibTeX XMLCite \textit{D. Gröger}, Result. Math. 75, No. 4, Paper No. 170, 9 p. (2020; Zbl 1480.12008) Full Text: DOI
Joshi, Santosh B.; Ritelli, Daniele Hypergeometric identities related to Roberts reductions of hyperelliptic integrals. (English) Zbl 1453.33010 Result. Math. 75, No. 4, Paper No. 169, 25 p. (2020). Reviewer: Thomas Ernst (Uppsala) MSC: 33C65 33C05 33E05 PDFBibTeX XMLCite \textit{S. B. Joshi} and \textit{D. Ritelli}, Result. Math. 75, No. 4, Paper No. 169, 25 p. (2020; Zbl 1453.33010) Full Text: DOI
Benahmadi, Abdelhadi; Ghanmi, Allal Dual of 2D fractional Fourier transform associated to Itô-Hermite polynomials. (English) Zbl 1473.44005 Result. Math. 75, No. 4, Paper No. 168, 11 p. (2020). Reviewer: D. L. Suthar (Dessie) MSC: 44A20 33C45 33C47 42B10 32A36 PDFBibTeX XMLCite \textit{A. Benahmadi} and \textit{A. Ghanmi}, Result. Math. 75, No. 4, Paper No. 168, 11 p. (2020; Zbl 1473.44005) Full Text: DOI arXiv
Pérez-Barral, Olga Some problems on ruled hypersurfaces in nonflat complex space forms. (English) Zbl 1452.53017 Result. Math. 75, No. 4, Paper No. 167, 11 p. (2020). MSC: 53B25 53C42 53C55 PDFBibTeX XMLCite \textit{O. Pérez-Barral}, Result. Math. 75, No. 4, Paper No. 167, 11 p. (2020; Zbl 1452.53017) Full Text: DOI arXiv
Rovenski, Vladimir; Stepanov, Sergey; Tsyganok, Irina On evolution equations under the Hamilton’s Ricci flow. (English) Zbl 1467.53105 Result. Math. 75, No. 4, Paper No. 166, 12 p. (2020). Reviewer: Yun Myung Oh (Berrien Springs) MSC: 53E20 53C20 53C25 53C40 PDFBibTeX XMLCite \textit{V. Rovenski} et al., Result. Math. 75, No. 4, Paper No. 166, 12 p. (2020; Zbl 1467.53105) Full Text: DOI
Zeng, Fanqi Rigid properties of generalized \(\tau \)-quasi Ricci-harmonic metrics. (English) Zbl 1452.53042 Result. Math. 75, No. 4, Paper No. 165, 23 p. (2020). MSC: 53C21 53C25 53C24 PDFBibTeX XMLCite \textit{F. Zeng}, Result. Math. 75, No. 4, Paper No. 165, 23 p. (2020; Zbl 1452.53042) Full Text: DOI arXiv
Michta, Mariusz; Motyl, Jerzy Selection properties and set-valued Young integrals of set-valued functions. (English) Zbl 1462.28013 Result. Math. 75, No. 4, Paper No. 164, 21 p. (2020). Reviewer: Natalia Skripnik (Odessa) MSC: 28B20 26B30 26E25 47H04 60H10 PDFBibTeX XMLCite \textit{M. Michta} and \textit{J. Motyl}, Result. Math. 75, No. 4, Paper No. 164, 21 p. (2020; Zbl 1462.28013) Full Text: DOI
Wernz, Annalena Hermitian theta series and Maaß spaces under the action of the maximal discrete extension of the Hermitian modular group. (English) Zbl 1457.11055 Result. Math. 75, No. 4, Paper No. 163, 9 p. (2020). MSC: 11F55 11F27 PDFBibTeX XMLCite \textit{A. Wernz}, Result. Math. 75, No. 4, Paper No. 163, 9 p. (2020; Zbl 1457.11055) Full Text: DOI arXiv
Nikodem, Kazimierz; Rajba, Teresa Ohlin-type theorem for convex set-valued maps. (English) Zbl 1451.26014 Result. Math. 75, No. 4, Paper No. 162, 9 p. (2020). MSC: 26A51 26D15 39B62 PDFBibTeX XMLCite \textit{K. Nikodem} and \textit{T. Rajba}, Result. Math. 75, No. 4, Paper No. 162, 9 p. (2020; Zbl 1451.26014) Full Text: DOI
Kim, Ju Myung; Lee, Keun Young; Zheng, Bentuo Banach compactness and Banach nuclear operators. (English) Zbl 1467.47008 Result. Math. 75, No. 4, Paper No. 161, 27 p. (2020). Reviewer: Elhadj Dahia (Bou Saâda) MSC: 47B07 47B10 47L20 PDFBibTeX XMLCite \textit{J. M. Kim} et al., Result. Math. 75, No. 4, Paper No. 161, 27 p. (2020; Zbl 1467.47008) Full Text: DOI
Mahmudov, N. I.; Udhayakumar, R.; Vijayakumar, V. On the approximate controllability of second-order evolution hemivariational inequalities. (English) Zbl 1453.93023 Result. Math. 75, No. 4, Paper No. 160, 18 p. (2020). MSC: 93B05 93C20 PDFBibTeX XMLCite \textit{N. I. Mahmudov} et al., Result. Math. 75, No. 4, Paper No. 160, 18 p. (2020; Zbl 1453.93023) Full Text: DOI
Mao, Guo-Shuai On two congruences involving Apéry and Franel numbers. (English) Zbl 1461.11007 Result. Math. 75, No. 4, Paper No. 159, 11 p. (2020). MSC: 11A07 05A10 11B65 PDFBibTeX XMLCite \textit{G.-S. Mao}, Result. Math. 75, No. 4, Paper No. 159, 11 p. (2020; Zbl 1461.11007) Full Text: DOI arXiv
Şirikçi, Nil İpek Displaceability of certain constant sectional curvature Lagrangian submanifolds. (English) Zbl 1452.53069 Result. Math. 75, No. 4, Paper No. 158, 12 p. (2020). MSC: 53D12 PDFBibTeX XMLCite \textit{N. İ. Şirikçi}, Result. Math. 75, No. 4, Paper No. 158, 12 p. (2020; Zbl 1452.53069) Full Text: DOI
Câmara, M. Cristina; Kliś-Garlicka, Kamila; Łanucha, Bartosz; Ptak, Marek Compressions of multiplication operators and their characterizations. (English) Zbl 07271450 Result. Math. 75, No. 4, Paper No. 157, 22 p. (2020). MSC: 47B32 47B35 30H10 PDFBibTeX XMLCite \textit{M. C. Câmara} et al., Result. Math. 75, No. 4, Paper No. 157, 22 p. (2020; Zbl 07271450) Full Text: DOI
Draganov, Borislav R. Direct estimates of the weighted simultaneous approximation by the Baskakov operator. (English) Zbl 1454.41003 Result. Math. 75, No. 4, Paper No. 156, 31 p. (2020). Reviewer: Zoltán Finta (Cluj-Napoca) MSC: 41A17 41A25 41A28 41A35 41A81 PDFBibTeX XMLCite \textit{B. R. Draganov}, Result. Math. 75, No. 4, Paper No. 156, 31 p. (2020; Zbl 1454.41003) Full Text: DOI
Guo, Victor J. W.; Schlosser, Michael J. A new family of \(q\)-supercongruences modulo the fourth power of a cyclotomic polynomial. (English) Zbl 1469.11032 Result. Math. 75, No. 4, Paper No. 155, 12 p. (2020). MSC: 11B65 11A07 33D15 PDFBibTeX XMLCite \textit{V. J. W. Guo} and \textit{M. J. Schlosser}, Result. Math. 75, No. 4, Paper No. 155, 12 p. (2020; Zbl 1469.11032) Full Text: DOI
Li, Ying; Mo, Xiaohuan On isoperimetric problem in a 2-dimensional Finsler space of Funk type. (English) Zbl 1452.53064 Result. Math. 75, No. 4, Paper No. 154, 18 p. (2020). MSC: 53C60 51M25 51M10 PDFBibTeX XMLCite \textit{Y. Li} and \textit{X. Mo}, Result. Math. 75, No. 4, Paper No. 154, 18 p. (2020; Zbl 1452.53064) Full Text: DOI
Verhulst, Nikolaas D. Counting finite-dimensional algebras over finite field. (English) Zbl 1456.17007 Result. Math. 75, No. 4, Paper No. 153, 8 p. (2020). Reviewer: Steven C. Althoen (Dexter) MSC: 17A99 PDFBibTeX XMLCite \textit{N. D. Verhulst}, Result. Math. 75, No. 4, Paper No. 153, 8 p. (2020; Zbl 1456.17007) Full Text: DOI arXiv
Heineken, Sigrid B.; Morillas, Patricia M.; Tarazaga, Pablo Balanced frames: a useful tool in signal processing with good properties. (English) Zbl 1462.42052 Result. Math. 75, No. 4, Paper No. 152, 29 p. (2020). Reviewer: Antonio Galbis (Valencia) MSC: 42C15 15A03 15A60 94A05 94A12 94A13 PDFBibTeX XMLCite \textit{S. B. Heineken} et al., Result. Math. 75, No. 4, Paper No. 152, 29 p. (2020; Zbl 1462.42052) Full Text: DOI arXiv
Ciepliński, Krzysztof On Ulam stability of a functional equation. (English) Zbl 1451.39024 Result. Math. 75, No. 4, Paper No. 151, 10 p. (2020). MSC: 39B82 39B52 39B72 PDFBibTeX XMLCite \textit{K. Ciepliński}, Result. Math. 75, No. 4, Paper No. 151, 10 p. (2020; Zbl 1451.39024) Full Text: DOI
Laczkovich, M. Vector valued polynomials, exponential polynomials and vector valued harmonic analysis. (English) Zbl 1456.43003 Result. Math. 75, No. 4, Paper No. 150, 24 p. (2020). Reviewer: Mohammad Sal Moslehian (Mashhad) MSC: 43A45 22A20 39B52 46G25 PDFBibTeX XMLCite \textit{M. Laczkovich}, Result. Math. 75, No. 4, Paper No. 150, 24 p. (2020; Zbl 1456.43003) Full Text: DOI arXiv
Jabbari, Ali Positive type and positive definite functions on matrix valued group algebras. (English) Zbl 1460.43005 Result. Math. 75, No. 4, Paper No. 149, 24 p. (2020). MSC: 43A35 PDFBibTeX XMLCite \textit{A. Jabbari}, Result. Math. 75, No. 4, Paper No. 149, 24 p. (2020; Zbl 1460.43005) Full Text: DOI
Falcone, Giovanni; Figula, Ágota; Hannusch, Carolin Steiner loops of affine type. (English) Zbl 1451.05026 Result. Math. 75, No. 4, Paper No. 148, 24 p. (2020). MSC: 05B07 20N05 51E10 PDFBibTeX XMLCite \textit{G. Falcone} et al., Result. Math. 75, No. 4, Paper No. 148, 24 p. (2020; Zbl 1451.05026) Full Text: DOI
Selmi, Bilel Some new characterizations of Olsen’s multifractal functions. (English) Zbl 1451.28008 Result. Math. 75, No. 4, Paper No. 147, 15 p. (2020). MSC: 28A80 28A20 28A75 28A78 49Q15 PDFBibTeX XMLCite \textit{B. Selmi}, Result. Math. 75, No. 4, Paper No. 147, 15 p. (2020; Zbl 1451.28008) Full Text: DOI
Yu, Yuncai Pointwise wavelet estimation of density function with change-points based on NA and biased sample. (English) Zbl 1452.62299 Result. Math. 75, No. 4, Paper No. 146, 14 p. (2020). MSC: 62G08 62G20 42C40 PDFBibTeX XMLCite \textit{Y. Yu}, Result. Math. 75, No. 4, Paper No. 146, 14 p. (2020; Zbl 1452.62299) Full Text: DOI
O’Hara, Jun Pompeiu’s theorem and the moduli space of triangles. (English) Zbl 1454.51010 Result. Math. 75, No. 4, Paper No. 145, 11 p. (2020). Reviewer: Cătălin Barbu (Bacau) MSC: 51M04 PDFBibTeX XMLCite \textit{J. O'Hara}, Result. Math. 75, No. 4, Paper No. 145, 11 p. (2020; Zbl 1454.51010) Full Text: DOI arXiv
Nakamura, Hiroaki; Ogawa, Hiroyuki On generalized median triangles and tracing orbits. (English) Zbl 1454.51013 Result. Math. 75, No. 4, Paper No. 144, 22 p. (2020). Reviewer: Cătălin Barbu (Bacau) MSC: 51M15 51N20 12F05 43A32 PDFBibTeX XMLCite \textit{H. Nakamura} and \textit{H. Ogawa}, Result. Math. 75, No. 4, Paper No. 144, 22 p. (2020; Zbl 1454.51013) Full Text: DOI arXiv
Castrillón López, Marco; Gadea, P. M.; Rosado María, María Eugenia Lorentzian symmetric spaces which are Einstein-Yang-Mills with respect to invariant metric connections. (English) Zbl 1459.53055 Result. Math. 75, No. 4, Paper No. 143, 27 p. (2020). Reviewer: Zdeněk Dušek (České Budějovice) MSC: 53C35 53C30 53C50 70S15 PDFBibTeX XMLCite \textit{M. Castrillón López} et al., Result. Math. 75, No. 4, Paper No. 143, 27 p. (2020; Zbl 1459.53055) Full Text: DOI
Landjev, Ivan; Rousseva, Assia A general construction for blocking sets in finite affine geometries. (English) Zbl 1451.51004 Result. Math. 75, No. 4, Paper No. 142, 12 p. (2020). MSC: 51E21 51E22 51E15 51E23 94B65 PDFBibTeX XMLCite \textit{I. Landjev} and \textit{A. Rousseva}, Result. Math. 75, No. 4, Paper No. 142, 12 p. (2020; Zbl 1451.51004) Full Text: DOI
Głąb, Szymon; Marchwicki, Jacek Cardinal functions of purely atomic measures. (English) Zbl 1454.40001 Result. Math. 75, No. 4, Paper No. 141, 26 p. (2020). Reviewer: George Stoica (Saint John) MSC: 40A05 28A12 11K31 PDFBibTeX XMLCite \textit{S. Głąb} and \textit{J. Marchwicki}, Result. Math. 75, No. 4, Paper No. 141, 26 p. (2020; Zbl 1454.40001) Full Text: DOI arXiv
Aldea, Nicoleta Zermelo deformation of Hermitian metrics by holomorphic vector fields. (English) Zbl 1452.53018 Result. Math. 75, No. 4, Paper No. 140, 18 p. (2020). MSC: 53B40 53C60 53B35 53B50 32Q15 PDFBibTeX XMLCite \textit{N. Aldea}, Result. Math. 75, No. 4, Paper No. 140, 18 p. (2020; Zbl 1452.53018) Full Text: DOI
Tertychniy, Sergey I. Square root of the monodromy map associated with the equation of RSJ model of Josephson junction. (English) Zbl 1459.34193 Result. Math. 75, No. 4, Paper No. 139, 36 p. (2020). Reviewer: Vladimir P. Kostov (Nice) MSC: 34M04 34M15 34M35 44A20 PDFBibTeX XMLCite \textit{S. I. Tertychniy}, Result. Math. 75, No. 4, Paper No. 139, 36 p. (2020; Zbl 1459.34193) Full Text: DOI arXiv
Yurko, V. Inverse problems for differential operators with indefinite discontinuous weights. (English) Zbl 1477.34038 Result. Math. 75, No. 4, Paper No. 138, 13 p. (2020). MSC: 34A55 34L05 47E05 PDFBibTeX XMLCite \textit{V. Yurko}, Result. Math. 75, No. 4, Paper No. 138, 13 p. (2020; Zbl 1477.34038) Full Text: DOI
Aissi, Y.; Zeglami, D. D’Alembert’s matrix functional equation with an endomorphism on abelian groups. (English) Zbl 1451.39021 Result. Math. 75, No. 4, Paper No. 137, 17 p. (2020). MSC: 39B42 39B52 PDFBibTeX XMLCite \textit{Y. Aissi} and \textit{D. Zeglami}, Result. Math. 75, No. 4, Paper No. 137, 17 p. (2020; Zbl 1451.39021) Full Text: DOI
Manev, Mancho Ricci-like solitons with vertical potential on Sasaki-like almost contact B-metric manifolds. (English) Zbl 1453.53054 Result. Math. 75, No. 4, Paper No. 136, 16 p. (2020). MSC: 53C25 53D15 53C50 53E20 53D35 70G45 PDFBibTeX XMLCite \textit{M. Manev}, Result. Math. 75, No. 4, Paper No. 136, 16 p. (2020; Zbl 1453.53054) Full Text: DOI arXiv
Chang, Yanxun; Liu, Cen; Su, Zhanjun The perimeter and area of reduced spherical polygons of thickness \(\pi /2\). (English) Zbl 1453.52010 Result. Math. 75, No. 4, Paper No. 135, 20 p. (2020). Reviewer: Gabriela Cristescu (Arad) MSC: 52A55 51M25 PDFBibTeX XMLCite \textit{Y. Chang} et al., Result. Math. 75, No. 4, Paper No. 135, 20 p. (2020; Zbl 1453.52010) Full Text: DOI
Jerónimo-Castro, Jesús; Rojas-Tapia, Marco Antonio; Velasco-García, Ulises; Yee-Romero, Carlos An isoperimetric inequality for isoptic curves of convex bodies. (English) Zbl 1450.52001 Result. Math. 75, No. 4, Paper No. 134, 12 p. (2020). Reviewer: Pedro Martín Jiménez (Badajoz) MSC: 52A10 52A38 52A40 PDFBibTeX XMLCite \textit{J. Jerónimo-Castro} et al., Result. Math. 75, No. 4, Paper No. 134, 12 p. (2020; Zbl 1450.52001) Full Text: DOI
Peng, Chia-Kuei; Wu, Yingyi A one-dimensional singular non-CSC extremal Kähler metric can be isometrically imbedded into \(\mathbb{R}^3\) as a Weingarten surface. (English) Zbl 1447.53014 Result. Math. 75, No. 4, Paper No. 133, 10 p. (2020). MSC: 53A05 53A10 30F30 PDFBibTeX XMLCite \textit{C.-K. Peng} and \textit{Y. Wu}, Result. Math. 75, No. 4, Paper No. 133, 10 p. (2020; Zbl 1447.53014) Full Text: DOI
Movsisyan, Yuri; Pambuccian, Victor The geometry of point reflections and quasigroups. (English) Zbl 1477.20136 Result. Math. 75, No. 4, Paper No. 132, 19 p. (2020). Reviewer: Huberta Lausch (Grafing) MSC: 20N05 51M05 PDFBibTeX XMLCite \textit{Y. Movsisyan} and \textit{V. Pambuccian}, Result. Math. 75, No. 4, Paper No. 132, 19 p. (2020; Zbl 1477.20136) Full Text: DOI
Maronikolakis, K.; Nestoridis, V. An extension of the universal power series of Seleznev. (English) Zbl 1451.30114 Result. Math. 75, No. 4, Paper No. 131, 8 p. (2020). Reviewer: Vagia Vlachou (Patras) MSC: 30K05 30E10 PDFBibTeX XMLCite \textit{K. Maronikolakis} and \textit{V. Nestoridis}, Result. Math. 75, No. 4, Paper No. 131, 8 p. (2020; Zbl 1451.30114) Full Text: DOI arXiv