Dynamical Equations, Invariants and Spectrum Generating Algebras of Mechanical Systems with Position-Dependent Mass

We analyze the dynamical equations obeyed by a classical system with position-dependent mass. It is shown that there is a non-conservative force quadratic in the velocity associated to the variable mass. We construct the Lagrangian and the Hamiltonian for this system and find the modifications required in the Euler-Lagrange and Hamilton's equations to reproduce the appropriate Newton's dynamical law. Since the Hamiltonian is not time invariant, we get a constant of motion suited to write the dynamical equations in the form of the Hamilton's ones. The time-dependent first integrals of motion are then obtained from the factorization of such a constant. A canonical transformation is found to map the variable mass equations to those of a constant mass. As particular cases, we recover some recent results for which the dependence of the mass on the position was already unnoticed, and find new solvable potentials of the P\"oschl-Teller form which seem to be new. The latter are associated to either the su(1,1) or the su(2) Lie algebras depending on the sign of the Hamiltonian

[Review of] Bienvenido L. Lumbera. Tagalog Poetry: 1570-1898

Bienvenido Lumbera, in his Preface to this survey of Tagalog poetry, apologizes for the shortcomings of his book. Originally written twenty years ago as a doctoral dissertation, it does not take into account new information on Tagalog poetry and its discussion of precolonial poetry does not include new data on the oral poetry of contemporary Filipino groups. I have bailed myself out, say Lumbera, by persuading myself that many scholarly sins could be forgiven under the rubric of \u27pioneering.\u27\u27\u27 And indeed these omissions can be forgiven for what the reader gains in return is a pioneering study describing and analyzing the development of Tagalog poetry

Response: An Invitation to a Too-Long Postponed Conversation: Race and Composition by Octavio Pimentel

Octavio Pimentel’s “Racism and Composition: Redesigning the Composition Classroom to be more Culturally Inclusive” critically provokes pedagogical and programmatic questions by focusing on pressing issues of race and language within a historical context relevant to the field of rhetoric and composition