10,971 research outputs found
Exclusive processes in pp collisions in CMS
We report the results on the searches of exclusive production of low- and
high-mass pairs with the Compact Muon Solenoid (CMS) detector in proton-proton
collisions at = 7 TeV. The analyses comprise the central exclusive
production, the exclusive two-photon production of dileptons,
and , and the exclusive two-photon production of
pairs in the asymmetric decay channel. No diphotons
candidates are observed in data and an upper limit on the cross section is set
to 1.18 pb with 95% confidence level for 5.5 GeV and
2.5. In the measurement of exclusive dilepton production,
seventeen candidates are observed in data with 5.5 GeV
and 2.5, and the cross section for the exclusive dimuon production
is set to (stat.)
0.16 (syst.) 0.14 (lumi.) pb for 11.5 GeV,
4 GeV and 2.1, both in agreement with the
theoretical predictions. For high-mass systems, two events are observed in data
for the exclusive two-photon production of pairs for
4 GeV, 20 GeV. Moreover, the
study of the tail of the dilepton transverse momentum distribution resulted in
model-independent upper limits for the anomalous quartic gauge couplings, which
are of the order of 10.Comment: 7 pages, 6 figures, presented at the XXI International Workshop on
Deep-Inelastic Scattering and Related Subjects, April 2013, Marseille, Franc
Defects in Jackiw-Teitelboim Quantum Gravity
We classify and study defects in 2d Jackiw-Teitelboim gravity. We show these
are holographically described by a deformation of the Schwarzian theory where
the reparametrization mode is integrated over different coadjoint orbits of the
Virasoro group. We show that the quantization of each coadjoint orbit is
connected to 2d Liouville CFT between branes with insertions of Verlinde loop
operators. We also propose an interpretation for the exceptional orbits. We use
this perspective to solve these deformations of the Schwarzian theory,
computing their partition function and correlators. In the process, we define
two geometric observables: the horizon area operator and the geodesic
length operator . We show this procedure is structurally related to
the deformation of the particle-on-a-group quantum mechanics by the addition of
a chemical potential. As an example, we solve the low-energy theory of complex
SYK with a U(1) symmetry and generalize to the non-abelian case.Comment: 66 pages, v4: clarifications added, typos corrected, matches
published versio
Inequality of opportunity and growth
Theoretical and empirical studies exploring the effects of income inequality upon growth reach a disappointing inconclusive result. This paper postulates that one reason for this ambiguity is that income inequality is actually a composite measure of at least two different sorts of inequality: inequality of opportunity and inequality of returns to effort. These two types of inequality affect growth through opposite channels, so the relationship between income inequality and growth is positive or negative depending on which component is larger. We test this proposal using inequality-of-opportunity measures computed from the PSID database for 23 states of the U.S. in 1980 and 1990. We find robust support for a negative relationship between inequality of opportunity and growth, and a positive relationship between inequality of returns to effort and growth.income inequality; inequality of opportunity; economic growth.
Cosmological black holes and the direction of time
Macroscopic irreversible processes emerge from fundamental physical laws of
reversible character. The source of the local irreversibility seems to be not
in the laws themselves but in the initial and boundary conditions of the
equations that represent the laws. In this work we propose that the screening
of currents by black hole event horizons determines, locally, a preferred
direction for the flux of electromagnetic energy. We study the growth of black
hole event horizons due to the cosmological expansion and accretion of cosmic
microwave background radiation, for different cosmological models. We propose
generalized McVittie co-moving metrics and integrate the rate of accretion of
cosmic microwave background radiation onto a supermassive black hole over
cosmic time. We find that for flat, open, and closed Friedmann cosmological
models, the ratio of the total area of the black hole event horizons with
respect to the area of a radial co-moving space-like hypersurface always
increases. Since accretion of cosmic radiation sets an absolute lower limit to
the total matter accreted by black holes, this implies that the causal past and
future are not mirror symmetric for any spacetime event. The asymmetry causes a
net Poynting flux in the global future direction; the latter is in turn related
to the ever increasing thermodynamic entropy. Thus, we expose a connection
between four different "time arrows": cosmological, electromagnetic,
gravitational, and thermodynamic.Comment: 13 pages, 2 figures in Foundations of Science (2017
Long-range-corrected hybrids including RPA correlation
We recently demonstrated a connection between the random phase approximation
(RPA) and coupled cluster theory [J. Chem. Phys. 129, 231101 (2008)]. Based on
this result, we here propose and test a simple scheme for introducing
long-range RPA correlation into density functional theory. Our method provides
good thermochemical results and models van derWaals interactions accurately.Comment: Accepted version of the manuscrip
- …