
Armaza, C., Hojman, S. A., Koch, B., & Zalaquett, N. (2016). On the possibility of nongeodesic motion of massless spinning tops. Class. Quantum Gravity, 33(14), 18 pp.
Abstract: The motion of spinning massless particles in gravitationally curved backgrounds is revisited by considering new types of constraints. Those constraints guarantee zero mass (P μP μ= 0) and they allow for the possibility of trajectories which are not simply null geodesics. To exemplify this previously unknown possibility, the equations of motion are solved for radial motion in Schwarzschild background. It is found that the particle experiences a spininduced energy shift, which is proportional to the Hawking temperature of the black hole background.



Chandia, O. (2011). The b ghost of the pure spinor formalism is nilpotent. Phys. Lett. B, 695(14), 312–316.
Abstract: The ghost for worldsheet reparametrization invariance is not a fundamental field in the pure spinor formalism. It is written as a combination of pure spinor variables which have conformal dimension two and such that it commutes with the BRST operator to give the worldsheet stress tensor. We show that the ghost variable defined in this way is nilpotent since the OPE of b with itself does not have singularities. (C) 2010 Elsevier B.V. All rights reserved.



Chandia, O., & Vallilo, B. C. (2016). Onshell type II supergravity from the ambitwistor pure spinor string. Class. Quantum Gravity, 33(18), 9 pp.
Abstract: We obtain all the type II supergravity constraints in the pure spinor ambitwistor string by imposing consistency of local worldsheet gauge symmetries.



Cortez, V., Saravia, G., & Vogel, E. E. (2014). Phase diagram and reentrance for the 3D EdwardsAnderson model using information theory. J. Magn. Magn. Mater., 372, 173–180.
Abstract: Data compressor techniques are used to study the phase diagram of the generalized EdwardsAnderson model in three dimensions covering the full range of mixture between ferromagnetic (concentration 1x) and antiferromagnetic interactions (concentration x). The recently proposed data compressor wlzip is used to recognize criticality by the maximum information content in the files storing the simulation processes. The method allows not only the characterization of the ferromagnetic to paramagnetic (FP) transition (x < 0.22, or x > 0.78) but also it equally well yields the spinglass to paramagnetic (SP) transition (0.22 < x < 0.78). A reentrance of a ferromagnetic phase into the spinglass phase is found in the vicinity of the multicritical point. The differences in the ways to apply the new method to FP and SP transitions are reported. A phase diagram for the entire range of x based entirely on the use of compression techniques is obtained and discussed. The advantages and disadvantages of the method of data compression as compared to other methods to deal with magnetic phase transitions are brought out and explained. (C) 2014 Elsevier B.V. All rights reserved.



Hojman, S. A., & Asenjo, F. A. (2017). Spinning particles coupled to gravity and the validity of the universality of free fall. Class. Quantum Gravity, 34(11), 8 pp.
Abstract: Recent experimental work has determined that free falling Rb87 atoms on Earth, with vertically aligned spins, follow geodesics, thus apparently ruling out spingravitation interactions. It is showed that while some spinning matter models coupled to gravitation referenced to in that work seem to be ruled out by the experiment, those same experimental results confirm theoretical results derived from a Lagrangian description of spinning particles coupled to gravity constructed over forty years ago. A proposal to carry out (similar but) different experiments which will help to test the validity of the universality of free fall as opposed to the correctness of the aforementioned Lagrangian theory, is presented.



Zalaquett, N., Hojman, S. A., & Asenjo, F. A. (2014). Spinning massive test particles in cosmological and general static spherically symmetric spacetimes. Class. Quantum Gravity, 31(8), 21 pp.
Abstract: A Lagrangian formalism is used to study the motion of a spinning massive particle in FriedmannRobertsonWalker and Godel spacetimes, as well as in a general Schwarzschildlike spacetime and in static spherically symmetric conformally flat spacetimes. Exact solutions for the motion of the particle and general exact expressions for the momenta and velocities are displayed for different cases. In particular, the solution for the motion in spherically symmetric metrics is presented in the equatorial plane. The exact solutions are found using constants of motion of the particle, namely its mass, its spin, its angular momentum, and a fourth constant, which is its energy when the metric is timeindependent, and a different constant otherwise. These constants are associated to Killing vectors. In the case of the motion on the FriedmannRobertsonWalker metric, a new constant of motion is found. This is the fourth constant which generalizes previously known results obtained for spinless particles. In the case of general Schwarzschildlike spacetimes, our results allow for the exploration of the case of the ReissnerNordstrom(Anti) de Sitter metric. Finally, for the case of the conformally flat spacetimes, the solution is explicitly evaluated for different metric tensors associated to a universe filled with static perfect fluids and electromagnetic radiation. For some combination of the values of the constants of motion the particle trajectories may exhibit spacelike velocity vectors in portions of the trajectories.

