5,532 research outputs found
Inverse Magnetic Catalysis in Bottom-Up Holographic QCD
We explore the effect of magnetic field on chiral condensation in QCD via a
simple bottom up holographic model which inputs QCD dynamics through the
running of the anomalous dimension of the quark bilinear. Bottom up holography
is a form of effective field theory and we use it to explore the dependence on
the coefficients of the two lowest order terms linking the magnetic field and
the quark condensate. In the massless theory, we identify a region of parameter
space where magnetic catalysis occurs at zero temperature but inverse magnetic
catalysis at temperatures of order the thermal phase transition. The model
shows similar non-monotonic behaviour in the condensate with B at intermediate
T as the lattice data. This behaviour is due to the separation of the meson
melting and chiral transitions in the holographic framework. The introduction
of quark mass raises the scale of B where inverse catalysis takes over from
catalysis until the inverse catalysis lies outside the regime of validity of
the effective description leaving just catalysis.Comment: 9 pages, 8 figure
Gravitational waves from eccentric intermediate-mass black hole binaries
If binary intermediate-mass black holes (IMBHs; with masses between 100 and
10^4 \Msun) form in dense stellar clusters, their inspiral will be detectable
with the planned Laser Interferometer Space Antenna (LISA) out to several Gpc.
Here we present a study of the dynamical evolution of such binaries using a
combination of direct -body techniques (when the binaries are well
separated) and three-body relativistic scattering experiments (when the
binaries are tight enough that interactions with stars occur one at a time). We
find that for reasonable IMBH masses there is only a mild effect on the
structure of the surrounding cluster even though the binary binding energy can
exceed the binding energy of the cluster. We demonstrate that, contrary to
standard assumptions, the eccentricity in the LISA band can be in {\em some}
cases as large as and that it induces a measurable phase
difference from circular binaries in the last year before merger. We also show
that, even though energy input from the binary decreases the density of the
core and slows down interactions, the total time to coalescence is short enough
(typically less than a hundred million years) that such mergers will be unique
snapshots of clustered star formation.Comment: Accepted for publication by ApJ Lett
Pass-Through And The Prediction Of Merger Price Effects
We use Monte Carlo experiments to study how pass-through can improve merger price predictions, focusing on the first order approximation (FOA) proposed in Jaffe and Weyl [2013]. FOA addresses the functional form misspecification that can exist in standard merger simulations. We find that the predictions of FOA are tightly distributed around the true price effects if pass-through is precise, but that measurement error in pass-through diminishes accuracy. As a comparison to FOA, we also study a methodology that uses pass-through to select among functional forms for use in simulation. This alternative also increases accuracy relative to standard merger simulation and proves more robust to measurement error
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