168,907 research outputs found
Topology Changing Process of Coalescing Black Holes on Eguchi-Hanson Space
We numerically study the event horizons of two kinds of five-dimensional
coalescing black hole solutions with different asymptotic structures: the
five-dimensional Kastor-Traschen solution (5DKT) and the coalescing black hole
solution on Eguchi-Hanson space (CBEH). Topologies of the spatial infinity are
and , respectively. We show that
the crease sets of event horizons are topologically in 5DKT and
in CBEH, respectively. If we choose the time slices
which respect space-time symmetry, the first contact points of the coalescing
process is a point in the 5DKT case but a in the CBEH case. We also
find that in CBEH, time slices can be chosen so that a black ring with topology can be also formed during a certain intermediate
period unlike the 5DKT.Comment: 13 pages, 17 figure
Thin Games with Symmetry and Concurrent Hyland-Ong Games
We build a cartesian closed category, called Cho, based on event structures.
It allows an interpretation of higher-order stateful concurrent programs that
is refined and precise: on the one hand it is conservative with respect to
standard Hyland-Ong games when interpreting purely functional programs as
innocent strategies, while on the other hand it is much more expressive. The
interpretation of programs constructs compositionally a representation of their
execution that exhibits causal dependencies and remembers the points of
non-deterministic branching.The construction is in two stages. First, we build
a compact closed category Tcg. It is a variant of Rideau and Winskel's category
CG, with the difference that games and strategies in Tcg are equipped with
symmetry to express that certain events are essentially the same. This is
analogous to the underlying category of AJM games enriching simple games with
an equivalence relations on plays. Building on this category, we construct the
cartesian closed category Cho as having as objects the standard arenas of
Hyland-Ong games, with strategies, represented by certain events structures,
playing on games with symmetry obtained as expanded forms of these arenas.To
illustrate and give an operational light on these constructions, we interpret
(a close variant of) Idealized Parallel Algol in Cho
Electroweak quark-lepton symmetry and weak topological-charge confinement in the Standard Model with Dirac neutrinos
The standard electroweak model with Dirac neutrinos is extended by way of the
principles of electroweak quark-lepton symmetry and weak topological-charge
confinement to account for quark-lepton charge relations which, if not
accidental, are indicative of charge structures. A mixing in quarks and leptons
of underlying integer local charges with integer weak topological charges
associated with an additive group Z_3, fixed by the anomaly cancellation
requirement, is discussed. It is found that the electroweak difference between
topological quarks and leptons is the nonequivalence between the topological
vacua of their weak field configurations, produced by a four-instanton which
carries the topological charge, induces the universal fractional piece of
charge distinguishing quarks from leptons, and breaks the underlying symmetry.
The constituent quarks of the standard model appear as coming from topological
quarks, via the weak four-instanton event. Dual transitions occur for leptons.
It is shown that several other fundamental problems left open in the standard
electroweak model with Dirac neutrinos are solved: the one-to-one
correspondence between quark and lepton flavors, the existence of three
generations, the conservation and ungauging of B-L, the electric charge
quantization, and the confinement of fractional electric charges.Comment: 23 pages, 1 figure, uses IJMPA.cl
Structure and stability of helices in square-well homopolymers
Recently, it has been demonstrated [Magee et al., Phys. Rev. Lett. 96, 207802
(2006)] that isolated, square-well homopolymers can spontaneously break chiral
symmetry and freeze into helical structures at sufficiently low temperatures.
This behavior is interesting because the square-well homopolymer is itself
achiral. In this work, we use event-driven molecular dynamics, combined with an
optimized parallel tempering scheme, to study this polymer model over a wide
range of parameters. We examine the conditions where the helix structure is
stable and determine how the interaction parameters of the polymer govern the
details of the helix structure. The width of the square well (proportional to
lambda) is found to control the radius of the helix, which decreases with
increasing well width until the polymer forms a coiled sphere for sufficiently
large wells. The helices are found to be stable for only a window of molecular
weights. If the polymer is too short, the helix will not form. If the polymer
is too long, the helix is no longer the minimum energy structure, and other
folded structures will form. The size of this window is governed by the chain
stiffness, which in this model is a function of the ratio of the monomer size
to the bond length. Outside this window, the polymer still freezes into a
locked structure at low temperature, however, unless the chain is sufficiently
stiff, this structure will not be unique and is similar to a glassy state.Comment: Submitted to Physical Review
- …