443,493 research outputs found
Comments on the Electroweak Phase Transition
We report on an investigation of various problems related to the theory of
the electroweak phase transition. This includes a determination of the nature
of the phase transition, a discussion of the possible role of higher order
radiative corrections and the theory of the formation and evolution of the
bubbles of the new phase. We find in particular that no dangerous linear terms
appear in the effective potential. However, the strength of the first order
phase transition is 2/3 times less than what follows from the one-loop
approximation. This rules out baryogenesis in the minimal version of the
electroweak theory.Comment: 14 pages, 2 figures (not included
Libya's conflicts enter a dangerous new phase
Recent advances by Khalifa Haftar's "Libyan Arab Armed Forces" in southern Libya are changing power relations in Libya in ways that undermine the UNâs ongoing attempts at brokering a political solution. Haftar's increasing influence implies he will be less open to concessions, while key forces in western Libya now perceive him as an existential threat. The Tripoli-based Government of National Accord (GNA), which has, to date, remained ambivalent towards Haftar despite his open opposition towards it, will come under increasing pressure from both adversaries and allies of Haftar to clarify its stance. The new configuration raises the risk of escalation on multiple fronts. Only the emergence of a stable balance of power can create the conÂditions for a political settlement. (Autorenreferat
Interplay of quantum and classical fluctuations near quantum critical points
For a system near a quantum critical point (QCP), above its lower critical
dimension , there is in general a critical line of second order phase
transitions that separates the broken symmetry phase at finite temperatures
from the disordered phase. The phase transitions along this line are governed
by thermal critical exponents that are different from those associated with the
quantum critical point. We point out that, if the effective dimension of the
QCP, ( is the Euclidean dimension of the system and the
dynamic quantum critical exponent) is above its upper critical dimension ,
there is an intermingle of classical (thermal) and quantum critical
fluctuations near the QCP. This is due to the breakdown of the generalized
scaling relation between the shift exponent of the critical
line and the crossover exponent , for by a \textit{dangerous
irrelevant interaction}. This phenomenon has clear experimental consequences,
like the suppression of the amplitude of classical critical fluctuations near
the line of finite temperature phase transitions as the critical temperature is
reduced approaching the QCP.Comment: 10 pages, 6 figures, to be published in Brazilian Journal of Physic
Efficient Quantum Computing of Complex Dynamics
We propose a quantum algorithm which uses the number of qubits in an optimal
way and efficiently simulates a physical model with rich and complex dynamics
described by the quantum sawtooth map. The numerical study of the effect of
static imperfections in the quantum computer hardware shows that the main
elements of the phase space structures are accurately reproduced up to a time
scale which is polynomial in the number of qubits. The errors generated by
these imperfections are more dangerous than the errors of random noise in gate
operations.Comment: revtex, 4 pages, 3 figure
Diquark condensation in two colour QCD
Unquenched lattice SU(2) is studied at nonzero chemical potential in the
strong coupling limit. The topic of diquark condensation is addressed analyzing
the probability distribution function of the diquark condensate. We present
results at zero external source without using any potentially dangerous
extrapolation procedure. We find strong evidences for a (high density) second
order phase transition where a diquark condensate appears, and show
quantitative agreement of lattice calculations with low-energy effective
Lagrangian calculations.Comment: 9 pages, 6 figures, to be published in the proceedings of the
``International Workshop on Non-Perturbative Methods and Lattice QCD'',
Guangzhou, China, 15-21 May 200
- âŚ