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Search Results: 1 - 10 of 25975 matches for " Cristina Martinez Ramirez "
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On the cohomology of Brill-Noether loci over Quot schemes
Cristina Martinez Ramirez
Mathematics , 2006,
Abstract: Let C be a smooth projective curve over the field of the complex numbers. We consider Brill-Noether loci over the moduli of maps from C to the Grassmannian G(m,n) and the corresponding Quot schemes of quotients of a trivial vector bundle on C compactifying the spaces of morphisms. We study in detail the case in which m=2, n=4. We prove results on the irreducibility and dimension of these Brill-Noether loci and we address explicit formulas for their cohomology classes. We study the existence problem of these spaces which is closely related with the problem of classification of vector bundles over curves.
Intersections numbers on the compact variety of rational ruled surfaces
Cristina Martinez Ramirez
Mathematics , 2006,
Abstract: We consider the Quot scheme, R_{d}, compactifying the space of degree d maps from the projective line to the Grassmannian of lines. We give an algorithm for computing the degree of R_{d} under a "generalized Pl\"ucker embedding", this is a certain Gromov-Witten invariant. The approach is to apply the Atiyah-Bott localization formula for the natural C^{*}-action on R_{d}. These numbers can be obtained directly from Vafa-Intriligator formula.
The degree of the variety of rational ruled surfaces and Gromov-Witten invariants
Cristina Martinez Ramirez
Mathematics , 2006,
Abstract: We compute the degree of the variety parametrizing rational ruled surfaces of degree d in the projective space by relating the problem to Gromov-Witten invariants and Quantum cohomology.
On Brill-Noether loci over Quot schemes and a Torelli theorem
Cristina Martinez Ramirez
Mathematics , 2007,
Abstract: We prove a non abelian Torelli type result for smooth projective curves by working in the derived category of some associated polarized Quot schemes and defining Brill-Noether loci and Abel-Jacobi maps on them.
On a stratification of the Kontsevich space of the Grassmannian G(2,4) and enumerative geometry
Cristina Martinez Ramirez
Mathematics , 2006,
Abstract: We study the geometry of the Kontsevich compactification of stable maps to the Grassmannian of lines in the projective space. We consider a stratification of this space. As an application we compute the degree of the variety parametrizing rational ruled surfaces with a minimal directix of degree d/2-1 by intersecting divisors in the moduli space of stable maps. For example, there are 128054031872040 rational ruled sextics passing through 25 points in $\mathbb{P}^{3}$ with a minimal directrix of degree 2.
Derived equivalences of Calabi-Yau fibrations
Cristina Martinez Ramirez,Andrey Todorov
Mathematics , 2009,
Abstract: We consider fibrations by abelian surfaces and K3 surfaces over a one dimensional base that are Calabi-Yau and we obtain dual fibrations that are derived equivalent to the original fibration. Finally, we relate the problem to mirror symmetry.
Some remarks on cyclic Galois coverings of the projective line over finite fields
Alberto Besana,Cristina Martinez Ramirez
Mathematics , 2012,
Abstract: We study cyclic finite Galois extensions of the rational function field of the projective line P^{1}(F_q) over a finite field F_q with q elements defined by considering quotient curves by finite subgroups of the projective linear group PGL(2,q), and we enumerate them expressing the count in terms of Stirling numbers.
Judgment Formation towards Health Risk Behaviors Concerning Obesity: An Integration Information Theory Approach  [PDF]
Aida A. Jimenez-Martinez, Perla Lizeth Hernandez-Cortes, Guadalupe E. Morales-Martinez, Ernesto O. Lopez-Ramirez
Health (Health) , 2017, DOI: 10.4236/health.2017.97076
A sample of 80 secondary students was required to take an information integration theory study to explore judgment formation toward health risk behavior regarding obesity. Here, twelve social scenarios containing a simulated actor were implemented (vignettes) having in mind a three factor experimental factor design (diet, weight and physical activity). Subjects had to read each vignette and provide an answer by marking ten points anchored scale to provide judgment on actors’ possible health risk outcome. Results showed that study participants valuated diet as the most relevant factor, followed by the description of weight and finally followed by the factor of physical activity. They impose systematic thinking to integrate different sources of information provided by factor manipulation in the vignettes by using a cognitive summative rule. Implications of this study result to clinical intervention in obesity as well as for theoretical considerations of cognitive models of health risk behavior are discussed in the present article.
Chemical and Morphological Study of PM10 Analysed by SEM-EDS  [PDF]
Roberto Ramirez-Leal, Maryanna Valle-Martinez, Martin Cruz-Campas
Open Journal of Air Pollution (OJAP) , 2014, DOI: 10.4236/ojap.2014.34012

Single particle characterization can provide information on the evolution of size distribution and chemical composition of pollution aerosol. The work described the use of Scanning Electron Microscopy (SEM) combined with X-ray Dispersive Energy Spectrometry (EDS) to characterize inorganic atmospheric particles samples collected on PM10 filters from January 2013 to October 2013 from three zones within the city of Hermosillo, Sonora. Specimens were initially processed by separating the collected particles from the filters by means of submersing a 2 cm2 section of each filter into isopropilic alcohol within a test tube for 5 minutes. Then, an aliquot of the suspension was placed over a sample holder and into the SEM. The different elements found amongst individual particles were Al, Ba, Ca, Cl, Cr, Cu, Fe, K, Mg, Mn, Na, Pb, S, Si, Ti and U. The predominant elements are Al (17.10 At%), Si (10.17 At%), Ba (5.90 At%), Fe (5.45 At%) and U (2.32 At%). The particles were classified into groups based on morphology and elemental composition: particles of aluminosilicate, salts of sodium chloride, sulfates, metal particles, barium and uranium. These particles morphology and chemical composition, illustrate an abundance of natural elements within the zone. However, some of the elements presented are directly related with human activities, and are of much interest from the public health and environmental perspectives. 

Codes, Horn's problem and Gromov-Witten invariants
Alberto Besana,Cristina Martinez
Mathematics , 2013,
Abstract: We study the Horn problem in the context of algebraic codes on a smooth projective curve defined over a finite field, reducing the problem to the representation theory of the special linear group $SL(2,F_q)$. We characterize the coefficients that appear in the Kronecker product of symmetric functions in terms of Gromov-Witten invariants of the Hilbert scheme of points in the plane. In addition we classify all the algebraic codes defined over the rational normal curve.
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