%0 Journal Article %T Optimal and maximal singular curves %+ Institut de Mathématiques de Marseille (I2M) %+ Institut de Mathématiques de Toulon - EA 2134 (IMATH) %A Aubry, Yves %A Iezzi, Annamaria %< avec comité de lecture %@ 0271-4132 %J Contemporary mathematics %I American Mathematical Society %S Arithmetic, Geometry and Coding Theory %V 686 %P 31--43 %8 2017 %D 2017 %Z 1510.01853 %R 10.1090/conm/686/13776 %K finite field %K rational point %K maximal curve %K Singular curve %Z 14H20, 11G20, 14G15 %Z Mathematics [math]/Algebraic Geometry [math.AG]Journal articles %X Using an Euclidean approach, we prove a new upper bound for the number of closed points of degree 2 on a smooth absolutely irreducible projective algebraic curve defined over the finite field $\mathbb F_q$.This bound enables us to provide explicit conditions on $q, g$ and $\pi$ for the non-existence of absolutely irreducible projective algebraic curves defined over $\mathbb F_q$ of geometric genus $g$, arithmetic genus $\pi$ and with $N_q(g)+\pi-g$ rational points.Moreover, for $q$ a square, we study the set of pairs $(g,\pi)$ for which there exists a maximal absolutely irreducible projective algebraic curve defined over $\mathbb F_q$ of geometric genus $g$ and arithmetic genus $\pi$, i.e. with $q+1+2g\sqrt{q}+\pi-g$ rational points. %G English %2 https://hal.science/hal-01212624/document %2 https://hal.science/hal-01212624/file/Aubry_Iezzi.pdf %L hal-01212624 %U https://hal.science/hal-01212624 %~ UNIV-TLN %~ CNRS %~ UNIV-AMU %~ EC-MARSEILLE %~ I2M %~ I2M-2014- %~ IMATH %~ AMIDEX %~ TEST-HALCNRS %~ ANR