22,189 research outputs found
Reducing the Top Quark Mass Uncertainty with Jet Grooming
The measurement of the top quark mass has large systematic uncertainties
coming from the Monte Carlo simulations that are used to match theory and
experiment. We explore how much that uncertainty can be reduced by using jet
grooming procedures. We estimate the inherent ambiguity in what is meant by
Monte Carlo mass to be around 530 MeV without any corrections. This uncertainty
can be reduced by 60% to 200 MeV by calibrating to the W mass and a further 33%
to 140 MeV by applying soft-drop jet grooming (or by 20% more to 170 MeV with
trimming). At e+e- colliders, the associated uncertainty is around 110 MeV,
reducing to 50 MeV after calibrating to the W mass. By analyzing the tuning
parameters, we conclude that the importance of jet grooming after calibrating
to the W mass is to reduce sensitivity to the underlying event.Comment: 21 pages, 7 figure
Leggett-Garg inequalities for quantum fluctuating work
The Leggett-Garg inequalities serve to test whether or not quantum
correlations in time can be explained within a classical macrorealistic
framework. We apply this test to thermodynamics and derive a set of Leggett-
Garg inequalities for the statistics of fluctuating work done on a quantum
system unitarily driven in time. It is shown that these inequalities can be
violated in a driven two-level system, thereby demonstrating that there exists
no general macrorealistic description of quantum work. These violations are
shown to emerge within the standard Two-Projective-Measurement scheme as well
as for alternative definitions of fluctuating work that are based on weak
measurement. Our results elucidate the influences of temporal correlations on
work extraction in the quantum regime and highlight a key difference between
quantum and classical thermodynamics.Comment: v2, 1 figure, accepted version to appear in Entropy (Special Issue on
"Quantum Thermodynamics II"
Entropy production and time-asymmetry in the presence of strong interactions
It is known that the equilibrium properties of open classical systems that
are strongly coupled to a heat bath are described by a set of thermodynamic
potentials related to the system's Hamiltonian of mean force. By adapting this
framework to a more general class of non-equilibrium states, we show that the
equilibrium properties of the bath can be well-defined, even when the system is
arbitrarily far from equilibrium and correlated with the bath. These states,
which retain a notion of temperature, take the form of conditional equilibrium
distributions. For out-of-equilibrium processes we show that the average
entropy production quantifies the extent to which the system-bath state is
driven away from the conditional equilibrium distribution. In addition, we show
that the stochastic entropy production satisfies a generalised Crooks relation
and can be used to quantify time-asymmetry of correlated non-equilibrium
processes. These results naturally extend the familiar properties of entropy
production in weakly-coupled systems to the strong coupling regime.
Experimental measurements of the entropy production at strong coupling could be
pursued using optomechanics or trapped ion systems, which allow strong coupling
to be engineered.Comment: 8 pages, 1 figure, comments welcom
Time-reversal symmetric work distributions for closed quantum dynamics in the histories framework
A central topic in the emerging field of quantum thermodynamics is the
definition of thermodynamic work in the quantum regime. One widely used
solution is to define work for a closed system undergoing non-equilibrium
dynamics according to the two-point energy measurement scheme. However, due to
the invasive nature of measurement the two-point quantum work probability
distribution leads to inconsistencies with two pillars of thermodynamics: it
breaks the first law and the time-reversal symmetry expected for closed
dynamics. We here introduce the quantum histories framework as a method to
characterise the thermodynamic properties of the unmeasured, closed dynamics.
Extending the classical phase space trajectories to continuous power operator
trajectories allows us to derive an alternative quantum work distribution for
closed quantum dynamics that fulfils the first law and is time-reversal
symmetric. We find that the work distribution of the unmeasured dynamics leads
to deviations from the classical Jarzynski equality and can have negative
values highlighting distinctly non-classical features of quantum work.Comment: 18 pages, 2 figures, comments welcom
Non-perturbative computation of the bubble nucleation rate in the cubic anisotropy model
At first order phase transitions the transition proceeds through droplet
nucleation and growth. We discuss a lattice method for calculating the droplet
nucleation rate, including the complete dynamical factors. The method is
especially suitable for very strongly suppressed droplet nucleation, which is
often the case in physically interesting transitions. We apply the method to
the 3-dimensional cubic anisotropy model in a parameter range where the model
has a radiatively induced strong first order phase transition, and compare the
results with analytical approaches
Isomorphisms between pattern classes
Isomorphisms p between pattern classes A and B are considered. It is shown
that, if p is not a symmetry of the entire set of permutations, then, to within
symmetry, A is a subset of one a small set of pattern classes whose structure,
including their enumeration, is determined.Comment: 11 page
Should we campaign against sex robots?
In September 2015 a well-publicised Campaign Against Sex Robots (CASR) was launched. Modelled on the longer-standing Campaign to Stop Killer Robots, the CASR opposes the development of sex robots on the grounds that the technology is being developed with a particular model of female-male relations (the prostitute-john model) in mind, and that this will prove harmful in various ways. In this chapter, we consider carefully the merits of campaigning against such a technology. We make three main arguments. First, we argue that the particular claims advanced by the CASR are unpersuasive, partly due to a lack of clarity about the campaign’s aims and partly due to substantive defects in the main ethical objections put forward by campaign’s founder(s). Second, broadening our inquiry beyond the arguments proferred by the campaign itself, we argue that it would be very difficult to endorse a general campaign against sex robots unless one embraced a highly conservative attitude towards the ethics of sex, which is likely to be unpalatable to those who are active in the campaign. In making this argument we draw upon lessons from the campaign against killer robots. Finally, we conclude by suggesting that although a generalised campaign against sex robots is unwarranted, there are legitimate concerns that one can raise about the development of sex robots
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