Recent works

- Bianchi type A hyper-symplectic and hyper-K\"ahler metrics in 4D , (with Luis C. de Andre's, Marisa Ferna'ndez, Jose A. Santisteban, Luis Ugarte and Dimiter Vassilev), to appear in Class. Quant. Grav. arXiv:arXiv:1102.1518.

- Compact supersymmetric solutions of the heterotic equations of motion in dimensions 7 and 8, (with M. Ferna'ndez, L. Ugarte and R. Villacampa), Adv. Theor. Math. Phys. (2011). arXiv:0806.4356.

- HKT manifolds with holonomy SL(n,H), (with A. Petkov), International Mathematics Research Notices, 2011; doi: 10.1093/imrn/rnr160. arXiv:arXiv:1010.5052.

- The twistor space of a quaternionic contact manifold, (with J. Davidov and I. Minchev), Quart. J. Math. (2011), 1–18; doi:10.1093/qmath/har012 arXiv:arXiv:1010.4994.

- Heterotic supersymmetry, anomaly cancellation and equations of motion, Phys. Lett. B685 (2010), 190-196. arXiv:0908.2927.

- Quaternionic contact manifolds with a closed fundamental 4-form, (with D. Vassilev), Bull. London Math. Soc., 42 (6) (2010), 1021–1030. arXiv:0810.3888,.

- Conformal quaternionic contact curvature and the local sphere theorem, (with D. Vassilev), Journal de Mathe'matiques Pures et Applique'es (JMPA) 93 (2010), 277-307. arXiv:0707.1289.

- Extremals for the Sobolev inequality on the seven dimensional quaternionic Heisenberg group and the quaternionic contact Yamabe problem, (with I. Minchev and D. Vassilev), J. Eur. Math. Soc. (JEMS) 12 (2010), 1041–1067. math.DG/0703044

- Compact supersymmetric solutions of the heterotic equations of motion in dimension 5, (with M. Ferna'ndez, L. Ugarte and R. Villacampa), Nuclear Physics B820 (2009), 483-502. arXiv:0811.2137.

- Non-Kaehler Heterotic String Compactifications with non-zero fluxes and constant dilaton, (with M. Ferna'ndez, L. Ugarte and R. Villacampa), Comm. Math. Phys. 288 (2009), 677-697. arXiv:0804.1648

- Conformal Paracontact curvature and the local flatness theorem, (with D. Vassilev and S. Zamkovoy), Geom. Dedicata 144 (2010), 79-100. arXiv:0707.3773

- Curvature decomposition of $G_2$ manifolds (with R. Cleyton), J. Geom. Phys. 58 (2008), 1429-1449. math.DG/0702289.

- Nearly hypo structures and compact Nearly K\"ahler 6-manifolds with conical singularities (with M. Fernandez, V. Munos and L. Ugarte), J. London Math. Soc. 78 (2008), 580-604. math.DG/0602160.

- Conformal equivalence between certain geometries in dimension 6 and 7, (with R. Cleyton), Math. Res. Lett. 15 (2008), 631-641. math.DG/0607487.

- Twistor and Reflector Spaces of Almost Para-Quaternionic Manifolds, (with I. Minchev and S. Zamkovoy), to appear in "Handbook of pseudo-Riemannian Geometry and Supersymmetry" to be published by the European Mathematical Society EMS in the series IRMA Lectures in Mathematics and Theoretical Physics. math.DG/0511657.

- SU(3)-structures on submanifolds of a Spin(7)-manifold, (with F. Martin Cabrera), Diff. Geom. Appl. 26 (2008), 113-132. math.DG/0510406.

- On the geometry of closed $G_2$-structures, (with R. Cleyton), Commun. Math. Phys., 270 (2007), 53--67. math.DG/0306362.

- Locally conformal parallel $G_2$ and $Spin(7)$ manifolds, (with M. Parton and P. Piccinni), Math. Res. Lett., 13 (2006), 167--177. math.DG/0509038.

- Hyper-ParaHermitian manifolds with torsion, (with V. Tsanov and S. Zamkovoy), J. Geom. Phys. 56, (2006), 670-690. math.DG/0405585.

- Para-Hermitian and Para-Quaternionic manifolds, (with S. Zamkovoy), Diff. Geom. Appl. 23 (2005), 205-234. math.DG/0310415.

- $SU(3)$-instantons and $G_2, Spin(7)$ heterotic string solitons, (with P. Ivanov), Commun. Math. Phys. 259 (2005), 79-102. math.DG/0312094.

- Connection with torsion, parallel spinors and geometry of Spin(7) manifolds, Math. Res. Lett. 11 (2004), 171--186. math.DG/0111216.

- Quaternionic K\"ahler and hyperK\"ahler manifolds with torsion and twistor spaces, (with I. Minchev), J. reine angew. Math. 567 (2004), 215-233, math.DG/0112157.

- Deformations of generalized calibrations and compact non-Kahler manifolds with vanishing first Chern class, (with J. Gutowski and G. Papadopoulos), Asian J. Math. 7 (2003), 39-80, math.DG/0205012.

- Almost contact manifolds, connections with torsion, and parallel spinors, (with Th. Friedrich), J. reine angew. Math. 559 (2003), 217-236, math.DG/0111131.

- Killing spinor equations in dimension 7 and geometry of integrable $G_2$ manifolds, (with Th. Friedrich), J. Geom. Phys. 48 (2003), 1-11, math.DG/0112201

- Weyl structure with positive Ricci tensor, (with B. Alexandrov), Diff. Geom. Appl. 18 (2003), 343-350, math.DG/9902033.

- Parallel spinors and connections with skew-symmetric torsion in string theory, (with Th. Friedrich), Asian J. Math. 6 (2002), 303-336, math.DG/0102142.

- Geometry of Quaternionic Kaehler connections with torsion, J. Geom. Phys. 41 (2002), 235-257, math.DG/0003214.

- A no-go theorem for string warped compactification, (with G.Papadopoulos), Phys. Lett. B 497 (2001) 309-316, hep-th/0008232.

- Vanishing theorems and String Backgrounds, (with G.Papadopoulos), Class. Quantum Gravity 18 (2001), 1089-1110, math.DG/0010038.

- Harmonic spinors of Dirac operator of connection with torsion in dimension 4, (with P.Dalakov), Class. Quantum Gravity 18 (2001), 253-265, [PS]

- Vanishing theorems on Hermitian manifolds, (with B. Alexandrov), Diff. Geom. Appl. 14 (3) (2001), 251-265, math.DG/9901090.

- The Dolbeault operator on Hermitian spin surfaces, (with. B. Alexandrov and G. Grantcharov), Ann. Inst. Fourier (Grenoble) 51 1 (2001), 221-235, math.DG/9902005.

- Harmonic and holomorphic 1-forms on compact balanced Hermitian manifold (with G.Ganchev), Diff. Geom. Appl. 14 (1) (2001), 79-93. [PS]

- Holomorphic and Killing vector fields on compact balanced Hermitian manifolds, (with G.Ganchev), Int. J. Math. 11 (2000), 15-28. [PS]

- Dirac operators on Hermitian spin surfaces (with B. Alexandrov), Ann. Glob. Anal. Geom. 18 (2000), 529-539. [PS]

- Einstein-Weyl structures on certain compact conformal manifolds, Quart. J. Math. (Oxford) (2) 50 (1999), 457-462. [PS]

- Orthogonal complex structures on certain Riemannian 6-manifolds, (with V. Apostolov and G. Grantcharov), Diff. Geom. Appl. 11 (1999) 279-296. [PS]

- Riemannian manifold in which the skew-symmetric curvature operator has pointwise constant eigenvalues, (with I.Petrova), Geom. Dedicata 70 (1998), 269-282. [PS]

- Curvature properties of twistor spaces of quaternionic Kaehler manifolds, (with B. Alexandrov and G. Grantcharov), J. Geom. 62 (1998), 1-12. [PS]

- An estimate for the first eigenvalue of the Dirac operator on compact Riemannian spin manifold admitting parallel one form, (with B. Alexandrov and G. Grantcharov), J. Geom. Phys. 28 (1998), 263-270. [PS]

- Hermitian structures on twistor spaces, (with V. Apostolov and G. Grantcharov), Ann. Glob. Anal. Geom. 16 (1998), 291-308. [PS]

- Compact Hermitian surfaces of constant antiholomorphic sectional curvature, (with V.Apostolov and G.Ganchev), Proc. Amer. Math. Soc. 125 (1997), 3705-3714. [PS]

- Einstein-Hermitian surfaces and Hermitian Einstein-Weyl structures in dimension 4, (with P.Gauduchon), Mathematische Zeitschrift 226 (1997), 317-326. [PS]

- On the fundamental theorem for non-degenerate complex affine hypersurface immersions, Monatshefte Mathematics 123 (1997), 321-336. [PS]

- Riemannian manifolds in which certain curvature operator has constant eigenvalues along each circle, (with I.Petrova), Ann. Glob. Anal. Geom. 15 (1997), 157-171. [PS]