2,080 research outputs found
Flavorful hybrid anomaly-gravity mediation
We consider supersymmetric models where anomaly and gravity mediation give
comparable contributions to the soft terms and discuss how this can be realized
in a five-dimensional brane world. The gaugino mass pattern of anomaly
mediation is preserved in such a hybrid setup. The flavorful gravity-mediated
contribution cures the tachyonic slepton problem of anomaly mediation. The
supersymmetric flavor puzzle is solved by alignment. We explicitly show how a
working flavor-tachyon link can be realized with Abelian flavor symmetries and
give the characteristic signatures of the framework, including O(1) slepton
mass splittings between different generations and between doublets and
singlets. This provides opportunities for same flavor dilepton edge
measurements with missing energy at the Large Hadron Collider (LHC). Rare
lepton decay rates could be close to their current experimental limit. Compared
to pure gravity mediation, the hybrid model is advantageous because it features
a heavy gravitino which can avoid the cosmological gravitino problem of
gravity-mediated models combined with leptogenesis.Comment: 8 pages, 1 figure; v2: minor modifications to Sect. II, references
added, conclusions unchange
Early warning signs for saddle-escape transitions in complex networks
Many real world systems are at risk of undergoing critical transitions,
leading to sudden qualitative and sometimes irreversible regime shifts. The
development of early warning signals is recognized as a major challenge. Recent
progress builds on a mathematical framework in which a real-world system is
described by a low-dimensional equation system with a small number of key
variables, where the critical transition often corresponds to a bifurcation.
Here we show that in high-dimensional systems, containing many variables, we
frequently encounter an additional non-bifurcative saddle-type mechanism
leading to critical transitions. This generic class of transitions has been
missed in the search for early-warnings up to now. In fact, the saddle-type
mechanism also applies to low-dimensional systems with saddle-dynamics. Near a
saddle a system moves slowly and the state may be perceived as stable over
substantial time periods. We develop an early warning sign for the saddle-type
transition. We illustrate our results in two network models and epidemiological
data. This work thus establishes a connection from critical transitions to
networks and an early warning sign for a new type of critical transition. In
complex models and big data we anticipate that saddle-transitions will be
encountered frequently in the future.Comment: revised versio
Probing unitary two-time correlations in a neutral atom quantum simulator
Measuring unitarily-evolved quantum mechanical two-time correlations is
challenging in general. In a recent paper [P.~Uhrich {\em et al.}, Phys.\
Rev.~A {\bf 96}, 022127 (2017)], a considerable simplification of this task has
been pointed out to occur in spin- lattice models, bringing such
measurements into reach of state-of-the-art or near-future quantum simulators
of such models. Here we discuss the challenges of an experimental
implementation of measurement schemes of two-time correlations in quantum gas
microscopes or microtrap arrays. We propose a modified measurement protocol
that mitigates these challenges, and we rigorously estimate the accuracy of the
protocols by means of Lieb-Robinson bounds. On the basis of these bounds we
identify a parameter regime in which the proposed protocols allow for accurate
measurements of the desired two-time correlations.Comment: 15 pages, 2 figure
Pinning of Fermionic Occupation Numbers
The Pauli exclusion principle is a constraint on the natural occupation
numbers of fermionic states. It has been suspected since at least the 1970's,
and only proved very recently, that there is a multitude of further constraints
on these numbers, generalizing the Pauli principle. Here, we provide the first
analytic analysis of the physical relevance of these constraints. We compute
the natural occupation numbers for the ground states of a family of interacting
fermions in a harmonic potential. Intriguingly, we find that the occupation
numbers are almost, but not exactly, pinned to the boundary of the allowed
region (quasi-pinned). The result suggests that the physics behind the
phenomenon is richer than previously appreciated. In particular, it shows that
for some models, the generalized Pauli constraints play a role for the ground
state, even though they do not limit the ground-state energy. Our findings
suggest a generalization of the Hartree-Fock approximation
Brain rhythms of pain
Pain is an integrative phenomenon that results from dynamic interactions between sensory and contextual (i.e., cognitive, emotional, and motivational) processes. In the brain the experience of pain is associated with neuronal oscillations and synchrony at different frequencies. However, an overarching framework for the significance of oscillations for pain remains lacking. Recent concepts relate oscillations at different frequencies to the routing of information flow in the brain and the signaling of predictions and prediction errors. The application of these concepts to pain promises insights into how flexible routing of information flow coordinates diverse processes that merge into the experience of pain. Such insights might have implications for the understanding and treatment of chronic pain
A second Higgs from the Higgs portal
In the Higgs portal framework, the Higgs field generally mixes with the
Standard Model singlet leading to the existence of two states, one of which is
identified with the 125 GeV scalar observed at the LHC. In this work, we
analyse direct and indirect constraints on the second mass eigenstate and the
corresponding mixing angle. The existence of the additional scalar can be
beneficial as it can stabilise the otherwise-metastable electroweak vacuum. We
find parameter regions where all of the bounds, including the stability
constraints, are satisfied. We also study prospects for observing the decay of
the heavier state into a pair of the 125 GeV Higgs-like scalars.Comment: 16 pages, updated figures 3 and 4 with new limits from Higgs-searches
at the LHC, minor text adjustments, references adde
Dynamics of the critical Casimir force for a conserved order parameter after a critical quench
Fluctuation-induced forces occur generically when long-ranged correlations
(e.g., in fluids) are confined by external bodies. In classical systems, such
correlations require specific conditions, e.g., a medium close to a critical
point. On the other hand, long-ranged correlations appear more commonly in
certain non-equilibrium systems with conservation laws. Consequently, a variety
of non-equilibrium fluctuation phenomena, including fluctuation-induced forces,
have been discovered and explored recently. Here, we address a long-standing
problem of non-equilibrium critical Casimir forces emerging after a quench to
the critical point in a confined fluid with order-parameter-conserving dynamics
and non-symmetry-breaking boundary conditions. The interplay of inherent
(critical) fluctuations and dynamical non-local effects (due to density
conservation) gives rise to striking features, including correlation functions
and forces exhibiting oscillatory time-dependences. Complex transient regimes
arise, depending on initial conditions and the geometry of the confinement. Our
findings pave the way for exploring a wealth of non-equilibrium processes in
critical fluids (e.g., fluctuation-mediated self-assembly or aggregation). In
certain regimes, our results are applicable to active matter.Comment: 38 pages, 11 figure
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