19,853 research outputs found
An Exact Solution for Quantum Tunneling in a Dissipative System
Applying a technique developed recently [1,2] for an harmonic oscillator
coupled to a bath of harmonic oscillators, we present an exact solution for the
tunneling problem in an Ohmic dissipative system with inverted harmonic
potential. The result shows that while the dissipation tends to suppress the
tunneling, the Brownian motion tends to enhance the tunneling. Whether the
tunneling rate increases or not would then depend on the initial conditions. We
give a specific formula to calculate the tunneling probability determined by
various parameters and the initial conditions.Comment: The reference 2 is changed to Phys. Lett. from Phys. Rev. Let
Evolution of cooperation in spatial traveler's dilemma game
Traveler's dilemma (TD) is one of social dilemmas which has been well studied
in the economics community, but it is attracted little attention in the physics
community. The TD game is a two-person game. Each player can select an integer
value between and () as a pure strategy. If both of them select
the same value, the payoff to them will be that value. If the players select
different values, say and (), then the payoff to the
player who chooses the small value will be and the payoff to the other
player will be . We term the player who selects a large value as the
cooperator, and the one who chooses a small value as the defector. The reason
is that if both of them select large values, it will result in a large total
payoff. The Nash equilibrium of the TD game is to choose the smallest value
. However, in previous behavioral studies, players in TD game typically
select values that are much larger than , and the average selected value
exhibits an inverse relationship with . To explain such anomalous behavior,
in this paper, we study the evolution of cooperation in spatial traveler's
dilemma game where the players are located on a square lattice and each player
plays TD games with his neighbors. Players in our model can adopt their
neighbors' strategies following two standard models of spatial game dynamics.
Monte-Carlo simulation is applied to our model, and the results show that the
cooperation level of the system, which is proportional to the average value of
the strategies, decreases with increasing until is greater than the
threshold where cooperation vanishes. Our findings indicate that spatial
reciprocity promotes the evolution of cooperation in TD game and the spatial TD
game model can interpret the anomalous behavior observed in previous behavioral
experiments
Electroweak radiative corrections to triple photon production at the ILC
In this paper, we present the precision predictions for three photon
production in the standard model (SM) at the ILC including the full
next-to-leading (NLO) electroweak (EW) corrections, high order initial state
radiation (h.o.ISR) contributions and beamstrahlung effects. We present the LO
and the NLO EW+h.o.ISR+beamstrahlung corrected total cross sections for various
colliding energy when and the kinematic
distributions of final photons with at ILC, and find
that the NLO EW corrections, the h.o.ISR contributions and the beamstrahlung
effects are important in exploring the process .Comment: 6 pages, 8 figures, accepted for publication in Physics Letters
Top quark pair production at small transverse momentum in hadronic collisions
We investigate the transverse momentum resummation for top quark pair
production at hadron colliders using the soft-collinear effective theory and
the heavy-quark effective theory. We derive the factorization formula for
production at small pair transverse momentum, and show in detail the
procedure for calculating the key ingredient of the factorization formula: the
next-to-leading order soft functions. We compare our numerical results with
experimental data and find that they are consistent within theoretical and
experimental uncertainties. To verify the correctness of our resummation
formula, we expand it to the next-to-leading order and the
next-to-next-to-leading order, and compare those expressions with the exact
fixed-order results numerically. Finally, using the results of transverse
momentum resummation, we discuss the transverse-momentum-dependent
forward-backward asymmetry at the Tevatron.Comment: 39 pages, 7 figures, 1 table; final version in PR
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