## Publications

• Søren Eilers, Gunnar Restorff, Efren Ruiz, and Adam P.W. Sørensen, The complete classification of unital graph $$C^*$$-algebras: Geometric and strong, Soren Eilers, Gunnar Restorff, Efren Ruiz, and Adam P.W. Sorensen, The complete classification of unital graph C*-algebras: Geometric and strong, Duke Math. J. 170(11): pp. 2421–2517 (15 August 2021).

• Søren Eilers, James Gabe, Takeshi Katsura, Efren Ruiz, and Mark Tomforde, The extension problem for graph C*-algebras, Annals of K-theory, Vol. 5 (2020), No. 2, pp. 295–315.

• Sara E. Arklint, James Gabe, and Efren Ruiz, Hereditary C-subalgebras of graph C-algebras, J. Operator Theory 84 (1) (2020), pp. 99-126.

• James Gabe and Efren Ruiz, The unital Ext-groups and classification of C*-algebras, Glasgow Mathematical Journal , Volume 62 , Issue 1 , January 2020 , pp. 201 - 231.

• Sara E. Arklint, Søren Eilers, and Efren Ruiz, A dynamical characterization of diagonal preserving $$*$$-isomorphisms of graph $$C^*$$-algebras, Ergodic Theory and Dynam. Systems, 38 (2018), no.7, pp. 2401–2421.

• Søren Eilers, Gunnar Restorff, and Efren Ruiz, Automorphisms of Cuntz-Krieger algebras, J. Noncommut. Geom. 12 (2018), pp. 217–254.

• Søren Eilers, Gunnar Restorff, Efren Ruiz, and Adam P.W. Sørensen, Geometric classification of graph $$C^*$$-algebras over finite graphs, Canad. J. Math. Vol. 70 (2), 2018 pp. 294–353.

• Søren Eilers, Gunnar Restorff, Efren Ruiz, and Adam P.W. Sørensen, Invariance of the Cuntz splice, Math. Ann. (2017) 369, pp. 1061–1080.

• Søren Eilers, Gunnar Restorff, and Efren Ruiz, Ideal related K-theory with coefficients, Houston J. Math. 43 (2) 2017, pp. 403–458.

• Toke Meier Carlsen, Gunnar Restorff, and Efren Ruiz, Strong classification of purely infinite Cuntz-Krieger algebras, Trans. Amer. Math. Soc., Series B Volume 4, pp. 1–30 (March 17, 2017).

• Toke Meier Carlsen, Efren Ruiz, and Aidan Sims, Equivalence and stable isomorphism of groupoids, and diagonal-preserving stable isomorphisms of graph $$C^*$$-algebras and Leavitt path algebras, Proc. Amer. Math. Soc., 145, no. 4, pp. 1581–1592.

• James Gabe and Efren Ruiz, Classification of tight $$C^*$$-algebras over the one-point compactification of $$\mathbb{N}$$, J. Operator Theory 76 (2016), no. 1, pp. 175–204.

• Sren Eilers, Xin Li, and Efren Ruiz, The isomorphism problem for semigroup $$C^*$$-algebras of right-angled Artin monoids, Doc. Math. 21 (2016), pp. 309–343.

• Sara E. Arklint, Gunnar Restorff, and Efren Ruiz, Classification of real rank zero, purely infinite $$C^*$$-algebras with at most four primitive ideals, J. Funct. Anal. 271 (2016), no. 7, pp. 1921–1947.

• Jeffrey L. Boersema, Terry A. Loring, and Efren Ruiz, Pictures of KK-theory for real $$C^*$$-algebras and almost commuting matrices, Banach J. Math. Anal. 10 (2016), no. 1, pp. 27–47.

• Søren Eilers, Gunnar Restorff, and Efren Ruiz, Corrigendum to "Classifying $$C^*$$-algebras with both finite and infinite subquotients’’ [J. Funct. Anal. 265 (2013) 449–468], J. Funct. Anal. 270 (2016), no. 2, pp. 854–859.

• Sara E. Arklint and Efren Ruiz, Corners of Cuntz-Krieger algebras, Trans. Amer. Math. Soc. 367 (2015), no. 11, pp. 7595–7612.

• Efren Ruiz, Aidan Sims, and Adam P.W. Sørensen, UCT-Kirchberg algebras have nuclear dimension one, Adv. Math. 279 (2015), pp. 1–28.

• James Gabe, Efren Ruiz, Mark Tomforde, and Tristan Whalen, K-theory for Leavitt path algebras: computation and classification, J. Algebra 33 (2015), pp. 35–72.

• Efren Ruiz, Aidan Sims, Mark Tomforde, The nuclear dimension of graph $$C^*$$-algebras, Adv. Math. 272 (2015), pp. 96–123.

• Efren Ruiz and Mark Tomforde, Ideals in graph algebras, Algebr. Represent. Theory 17 (2014), no. 3, pp. 849–861.

• Søren Eilers, Gunnar Restorff, and Efren Ruiz, The ordered K-theory of a full extension, Canad. J. Math. 66 (2014), no. 3, pp. 596–625.

• Søren Eilers, Takeshi Katsura, Efren Ruiz, and Mark Tomforde, Identifying AF-algebras that are graph $$C^*$$-algebras, J. Funct. Anal. 266 (2014), pp. 3968–3996.

• Efren Ruiz and Mark Tomforde, Ideal-related K-theory for Leavitt path algebras and graph $$C^*$$-algebras, Indiana Univ. Math. J. 62 (2013), no. 5, pp. 1587–1620.

• Søren Eilers, Gunnar Restorff, and Efren Ruiz, Classifying $$C^*$$-algebras with both finite and infinite subquotients, J. Funct. Anal. 265 (2013), no. 3, pp. 449–468.

• Ping Wong Ng and Efren Ruiz, The automorphism group of a simple $$\mathcal{Z}$$-stable $$C^*$$-algebra, Trans. Amer. Math. Soc., 365 (2013), pp. 4081–4120.

• Efren Ruiz and Mark Tomforde, Classification of unital simple Leavitt path algebras of infinite graphs, J. Algebra, 384 (2013), pp. 45–83.

• Søren Eilers, Efren Ruiz, and Adam Sørensen, *Amplified graph $$C^*$$-algebras, Munster J. of Math., 5 (2012), pp. 121–150.

• Ping Wong Ng and Efren Ruiz, On the structure of the projective unitary group of the multiplier algebra of a simple stable $$C^*$$-algebra, J. Operator Theory 68 (2012), pp. 549–565.

• Sara E. Arklint, Gunnar Restorff, and Efren Ruiz, Filtrated K-theory for real rank zero $$C^*$$-algebras, Internat. J. Math., 23 (2012), no. 8, 1250078, 19 pp.

• Jeffrey L. Boersema, Efren Ruiz, and Peter J. Stacey, The classification of real purely infinite simple $$C^*$$-algebras, Documenta Math., 16 (2011), pp. 619–655.

• Jeffrey L. Boersema and Efren Ruiz, Stability of real $$C^*$$-algebras, Canad. Math. Bull., 54, no. 4 (2011), pp. 593–606.

• Søren Eilers, Gunnar Restorff, and Efren Ruiz, Nonsplitting in Kirchberg’s ideal-related KK-Theory, Canad. Math. Bull., 54 (2011), no. 1, pp. 68–81.

• Ping Wong Ng and Efren Ruiz, Simplicity of the projective unitary group of the multiplier algebra of a simple stable nuclear $$C^*$$-algebra, Rocky Mountain J. Math. 40 (2010), no. 5, pp. 1649–1665.

• Søren Eilers, Gunnar Restorff, and Efren Ruiz, On graph $$C^*$$-algebras with a linear ideal lattice, Bull. Malays. Math. Sci. Soc. 33(2) (2010), pp. 233–241.

• Søren Eilers, Gunnar Restorff, and Efren Ruiz, Classification of extensions of classifiable $$C^*$$-algebras, Adv. Math. 222 (2009), no. 6, pp. 2153–2172.

• Ping Wong Ng and Efren Ruiz, The structure of the unitary group of certain simple $$C^*$$-algebras, Houston J. Math 35 (4) 2009, pp. 1203–1232.

• Ping Wong Ng, Zhuang Niu, and Efren Ruiz, Simple unital $$C^*$$-algebras with the stable local finite dimensional property, J. Operator Theory 61(1) 2009, pp. 147-169.

• Ping Wong Ng and Efren Ruiz, The automorphism group of a simple tracially AI algebra, Comm. Math. Physics. 280 (2008) no. 2, pp. 427–444.

• Ping Wong Ng and Efren Ruiz, Extending maps in K-theory, Int. J. Pure and Applied Math. 41 No. 3 2007, pp. 419–442.

• Gunnar Restorff and Efren Ruiz, On Rordam’s classification of certain $$C^*$$-algebras with one non-trivial ideal, II, Math. Scand. 101 (2) 2007, pp. 280–292.

• Efren Ruiz, Homomorphisms and strong approximate unitary equivalence, Indiana Univ. Math. J. 56 No. 3 (2007) pp. 1333–1360.

• Efren Ruiz, A classification theorem for direct limits of extensions of circle algebras by purely infinite $$C^*$$-algebras, J. Operator theory 58 (2) 2007 pp. 311-349.

## Peer reviewed conference proceedings

• Søren Eilers, Gunnar Restorff, and Efren Ruiz, Classification of graph $$C^*$$-algebras with no more than four primitive ideals, Operator algebra and dynamics, pp. 89–129, Springer Proc. Math. Stat., 58, Springer, Heidelberg, 2013.

• Søren Eilers, Gunnar Restorff, Efren Ruiz, and Adam P.W. Sørensen, Filtered K-theory for graph algebras, 2016 Matrix annals, pp. 229–249, MATRIX Book Ser. 1, Springer, Cham, 2018.

## Publications with undergraduate students at UHH

• Damon Hay, Marissa Loving, Martin Montgomery, Efren Ruiz, and Katherine Todd, Non-stable K-theory for Leavitt path algebras (M. Loving [UHH student] and K. Todd [UHH student]) Rocky Mountain J. Math. 44 (2014), no. 6, pp. 1817–1850.

## Publications to Appear

• Toke Meier Carlsen, Efren Ruiz, Aidan Sims, and Mark Tomforde, Reconstruction of groupoids and C*-rigidity of dynamical system, To appear in Advances in Mathematics, Preprint version can be found at https://arxiv.org/pdf/1711.01052.pdf.