660 research outputs found
Commitment Vs. Flexibility
This paper studies the optimal trade-off between commitment and flexibility in an intertemporal consumption/savings choice model. Individuals expect to receive relevant information regarding their own situation and tastes - generating a value for flexibility - but also expect to suffer from temptations - generating a value for commitment. The model combines the representations of preferences for flexibility introduced by Kreps (1979) with its recent antithesis for commitment proposed by Gul and Pesendorfer (2002), which nests the hyperbolic discounting model. We set up and solve a mechanism design problem that optimizes over the set of consumption/saving options available to the individual each period. We characterize the conditions under which the solution takes a simple threshold form where minimum savings policies are optimal. Our analysis is also relevant for other issues such as situations with externalities or the problem faced by a 'paternalistic' planner, which may be important for thinking about some regulations such as forced minimum schooling laws.
Electroproduction of pseudoscalar mesons on the deuteron
A general analysis of polarization phenomena for coherent meson
electroproduction on deuterons, , where is a
pseudoscalar or -meson, is presented. The spin structure of the
electromagnetic current for -production at threshold is parametrized in
terms of specific (inelastic) threshold electromagnetic form factors which
depend on the momentum transfer squared and the effective mass of the produced
hadronic system. We give expressions for the structure functions of the
reaction (where the deuteron target is polarized) in
terms of these threshold form factors. The spin and isospin structures of the
amplitudes (where is a virtual photon) is
established in the framework of the impulse approximation and relationships
between meson electroproduction on deuterons and on nucleons are given. The
reaction of electroproduction on deuterons is investigated in detail
both at threshold and in the region of -isobar excitation, using the
effective Lagrangian approach for the calculation of the amplitudes of the
elementary process . Special attention is devoted to the
analysis of all standard contributions to the exclusive cross section for
, which are functions of the momentum transfer square, , of
the excitation energy of the produced hadrons and of the pion production angle,
in a region of relatively large momentum transfer. The sensitivity of these
contributions to different parametrizations of the form
factor as well as to the choice of potential is discussed.Comment: 44 pages 19 figure
Differential Games of Competition in Online Content Diffusion
Access to online contents represents a large share of the Internet traffic.
Most such contents are multimedia items which are user-generated, i.e., posted
online by the contents' owners. In this paper we focus on how those who provide
contents can leverage online platforms in order to profit from their large base
of potential viewers.
Actually, platforms like Vimeo or YouTube provide tools to accelerate the
dissemination of contents, i.e., recommendation lists and other re-ranking
mechanisms. Hence, the popularity of a content can be increased by paying a
cost for advertisement: doing so, it will appear with some priority in the
recommendation lists and will be accessed more frequently by the platform
users.
Ultimately, such acceleration mechanism engenders a competition among online
contents to gain popularity. In this context, our focus is on the structure of
the acceleration strategies which a content provider should use in order to
optimally promote a content given a certain daily budget. Such a best response
indeed depends on the strategies adopted by competing content providers. Also,
it is a function of the potential popularity of a content and the fee paid for
the platform advertisement service.
We formulate the problem as a differential game and we solve it for the
infinite horizon case by deriving the structure of certain Nash equilibria of
the game
Exploiting structure of maximum likelihood estimators for extreme value threshold selection
In order to model the tail of a distribution, one has to define the threshold above or below which an extreme value model produces a suitable fit. Parameter stability plots, whereby one plots maximum likelihood estimates of supposedly threshold-independent parameters against threshold, form one of the main tools for threshold selection by practitioners, principally due to their simplicity. However, one repeated criticism of these plots is their lack of interpretability, with pointwise confidence intervals being strongly dependent across the range of thresholds. In this article, we exploit the independent-increments structure of maximum likelihood estimators in order to produce complementary plots with greater interpretability, and a suggest simple likelihood-based procedure which allows for automated threshold selection
Access-Network Association Policies for Media Streaming in Heterogeneous Environments
We study the design of media streaming applications in the presence of
multiple heterogeneous wireless access methods with different throughputs and
costs. Our objective is to analytically characterize the trade-off between the
usage cost and the Quality of user Experience (QoE), which is represented by
the probability of interruption in media playback and the initial waiting time.
We model each access network as a server that provides packets to the user
according to a Poisson process with a certain rate and cost. Blocks are coded
using random linear codes to alleviate the duplicate packet reception problem.
Users must take decisions on how many packets to buffer before playout, and
which networks to access during playout. We design, analyze and compare several
control policies with a threshold structure. We formulate the problem of
finding the optimal control policy as an MDP with a probabilistic constraint.
We present the HJB equation for this problem by expanding the state space, and
exploit it as a verification method for optimality of the proposed control law.Comment: submitted to CDC 201
Finite-Horizon Optimal Transmission Policies for Energy Harvesting Sensors
In this paper, we derive optimal transmission policies for energy harvesting
sensors to maximize the utility obtained over a finite horizon. First, we
consider a single energy harvesting sensor, with discrete energy arrival
process, and a discrete energy consumption policy. Under this model, we show
that the optimal finite horizon policy is a threshold policy, and explicitly
characterize the thresholds, and the thresholds can be precomputed using a
recursion. Next, we address the case of multiple sensors, with only one of them
allowed to transmit at any given time to avoid interference, and derive an
explicit optimal policy for this scenario as well.Comment: Appeared in IEEE ICASSP 201
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