4,619 research outputs found
Reinforcement Learning Dynamics in Social Dilemmas
In this paper we replicate and advance Macy and Flache\'s (2002; Proc. Natl. Acad. Sci. USA, 99, 7229â7236) work on the dynamics of reinforcement learning in 2ïżœ2 (2-player 2-strategy) social dilemmas. In particular, we provide further insight into the solution concepts that they describe, illustrate some recent analytical results on the dynamics of their model, and discuss the robustness of such results to occasional mistakes made by players in choosing their actions (i.e. trembling hands). It is shown here that the dynamics of their model are strongly dependent on the speed at which players learn. With high learning rates the system quickly reaches its asymptotic behaviour; on the other hand, when learning rates are low, two distinctively different transient regimes can be clearly observed. It is shown that the inclusion of small quantities of randomness in players\' decisions can change the dynamics of the model dramatically.Reinforcement Learning; Replication; Game Theory; Social Dilemmas; Agent-Based; Slow Learning
Two-twistor particle models and free massive higher spin fields
We present D=3 and D=4 models for massive particles moving in a new type of
enlarged spacetime, with D-1 additional vector coordinates, which after
quantization lead to the towers of massive higher spin (HS) free fields. Two
classically equivalent formulations are presented: one with a hybrid
spacetime/bispinor geometry and a second described by a free two-twistor
dynamics with constraints. After quantization in the D=3 and D=4 cases, the
wave functions are given as functions on the SL(2,R) and SL(2,C) group
manifolds respectively, and describe arbitrary on-shell momenta and spin
degrees of freedom. Finally, the D=6 case and possible supersymmetric
extensions are mentioned.Comment: 37 pages, plain latex, v2. Text in Secs. 1 nd 4 enlarged, references
added. Version to appear in JHE
Contractions of Filippov algebras
We introduce in this paper the contractions of -Lie (or
Filippov) algebras and show that they have a semidirect
structure as their Lie algebra counterparts. As an example, we compute
the non-trivial contractions of the simple Filippov algebras. By
using the \.In\"on\"u-Wigner and the generalized Weimar-Woods contractions of
ordinary Lie algebras, we compare (in the simple case)
the Lie algebras Lie (the Lie algebra of inner endomorphisms
of ) with certain contractions
and of
the Lie algebra Lie associated with .Comment: plain latex, 36 pages. A few misprints corrected. This v3 is actually
v2 (v1 had been replaced by itself by error). To appear in J. Math. Phy
Supergeometry of Three Dimensional Black Holes
We show how the supersymmetric properties of three dimensional black holes
can be obtained algebraically. The black hole solutions are constructed as
quotients of the supergroup by a discrete subgroup of its
isometry supergroup. The generators of the action of the isometry supergroup
which commute with these identifications are found. These yield the
supersymmetries for the black hole as found in recent studies as well as the
usual geometric isometries. It is also shown that in the limit of vanishing
cosmological constant, the black hole vacuum becomes a null orbifold, a
solution previously discussed in the context of string theory.Comment: 12 pages, harvmac, discussion of rotating black hole added, some
minor corrections, reference adde
Blurred Lines Between Competition and Parasitism
Accurately describing the ecological relationships between species is more than mere semantics-doing so has profound practical and applied implications, not the least of which is that inaccurate descriptions can lead to fundamentally incorrect predicted outcomes of community composition and functioning. Accurate ecological classifications are particularly important in the context of global change, where species interactions can change rapidly following shifts in species composition. Here, we argue that many common ecological interactions-particularly competition and parasitism-can be easily confused and that we often lack empirical evidence for the full reciprocal interaction among species. To make our case and to propose a theoretical framework for addressing this problem, we use the interactions between lianas and trees, whose outcomes have myriad implications for the ecology and conservation of tropical forests (e.g., Schnitzer et al. 2015)
UWB antenna on 3D printed flexible substrate and foot phantom
An ultra-wideband (UWB) monopole antenna on an additive manufactured (AM) flexible substrate for foot wear application is proposed. The 3D printing of foot phantoms for the testing of this type of antennas is also introduced. Inexpensive fuse filament fabrication (FFF) technology is utilized for these developments. Flexible polylactic acid plastic filament (PLA) material is used for the antenna while transparent PLA for the phantom. The antenna is intended for integration into the footwear tongue. The UWB monopole antenna achieves -10dB input impedance matching from 3.1GHz to over 10.6GHz in freespace, on the foot phantom and on the real human body. Simulation and measurement confirm the ultra-wideband operation of the antenna
Killing spinors, the adS black hole and I(ISO(2,1)) gravity
We construct a supersymmetric extension of the
Chern-Simons gravity and show that certain particle-like solutions and the adS
black-hole solution of this theory are supersymmetric.Comment: 12 pages, uses phyzz
Supersymmetric spacetimes in 2+1 adS-supergravity models
We find a class of (2+1)-dimensional spacetimes admitting Killing spinors
appropriate to (2,0) adS-supergravity. The vacuum spacetimes include anti-de
Sitter (adS) space and charged extreme black holes, but there are many others,
including spacetimes of arbitrarily large negative energy that have only
conical singularities, and the spacetimes of fractionally charged point
particles. The non-vacuum spacetimes are those of self-gravitating solitons
obtained by coupling (2,0) adS supergravity to sigma-model matter. We show,
subject to a condition on the matter currents (satisfied by the sigma model),
and a conjecture concerning global obstructions to the existence of certain
types of spinor fields, that the mass of each supersymmetric spacetime
saturates a classical bound, in terms of the angular momentum and charge, on
the total energy of arbitrary field configurations with the same boundary
conditions, although these bounds may be violated quantum mechanically.Comment: 47 pages, phyzzx.tex, no figures
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