8,259 research outputs found
Large N and double scaling limits in two dimensions
Recently, the author has constructed a series of four dimensional
non-critical string theories with eight supercharges, dual to theories of light
electric and magnetic charges, for which exact formulas for the central charge
of the space-time supersymmetry algebra as a function of the world-sheet
couplings were obtained. The basic idea was to generalize the old matrix model
approach, replacing the simple matrix integrals by the four dimensional matrix
path integrals of N=2 supersymmetric Yang-Mills theory, and the Kazakov
critical points by the Argyres-Douglas critical points. In the present paper,
we study qualitatively similar toy path integrals corresponding to the two
dimensional N=2 supersymmetric non-linear sigma model with target space CP^n
and twisted mass terms. This theory has some very strong similarities with N=2
super Yang-Mills, including the presence of critical points in the vicinity of
which the large n expansion is IR divergent. The model being exactly solvable
at large n, we can study non-BPS observables and give full proofs that double
scaling limits exist and correspond to universal continuum limits. A complete
characterization of the double scaled theories is given. We find evidence for
dimensional transmutation of the string coupling in some non-critical string
theories. We also identify en passant some non-BPS particles that become
massless at the singularities in addition to the usual BPS states.Comment: 38 pages, including an introductory section that makes the paper
self-contained, two figures and one appendix; v2: typos correcte
The group of strong Galois objects associated to a cocommutative Hopf quasigroup
Let H be a cocommutative faithfully flat Hopf quasigroup in a strict
symmetric monoidal category with equalizers. In this paper we introduce the
notion of (strong) Galois H-object and we prove that the set of isomorphism
classes of (strong) Galois H-objects is a (group) monoid which coincides, in
the Hopf algebra setting, with the Galois group of H-Galois objects introduced
by Chase and Sweedler
The Case of HCO Isomers, Revisited: Solving the Mystery of the Missing Propadienone
To date, two isomers of HCO have been detected, namely, propynal
(HCCCHO) and cylclopropenone (c-HCO). A third, propadienone
(CHCCO), has thus far eluded observers despite the fact that it is the
lowest in energy of the three. This previously noted result is in contradiction
of the minimum energy principle, which posits that the abundances of isomers in
interstellar environments can be predicted based on their relative stabilities
- and suggests, rather, the importance of kinetic over thermodynamic effects in
explaining the role of such species.
Here, we report results of \textit{ab initio} quantum chemical calculations
of the reaction between H and (a) HCO, (b) HCO (both propynal and
propadienone), and (c) CHCHCO. We have found that, among all possible
reactions between atomic hydrogen and either propadienone or propynal, only the
destruction of propadienone is barrierless and exothermic. That this
destruction pathway is indeed behind the non-detection of CHCCO is further
suggested by our finding that the product of this process, the radical
CHCHCO, can subsequently react barrierlessly with H to form propenal
(CHCHCHO) which has, in fact, been detected in regions where the other two
HCO isomers are observed. Thus, these results not only shed light on a
previously unresolved astrochemical mystery, but also further highlight the
importance of kinetics in understanding the abundances of interstellar
molecules.Comment: ApJ, accepted: 14 pages, 2 figure
La motivación del alumnado a través de la satisfacción con la asignatura. Efecto sobre el rendimiento
El alto nivel de absentismo y la falta de motivación de los
alumnos son rasgos característicos de una realidad a la que nos
enfrentamos día a día. Este problema, agudizado por la cada vez
más cercana adaptación al Espacio Europeo de Educación
Superior, provoca la necesidad de que nos replanteemos la
forma de hacer las cosas en nuestra labor como docentes universitarios.
La presente experiencia persigue incrementar el interés
y la implicación del alumnado a través de un aumento de su
grado de satisfacción con la asignatura. Adicionalmente se
pretende comprobar cómo esta circunstancia puede redundar en
una mejora de las calificaciones obtenidas por los alumnos
- …