1,189 research outputs found
Symmetry energy of dense matter in holographic QCD
We study the nuclear symmetry energy of dense matter using holographic QCD.
To this end, we consider two flavor branes with equal quark masses in a
D4/D6/D6 model. We find that at all densities the symmetry energy monotonically
increases. At small densities, it exhibits a power law behavior with the
density, .Comment: 9 pages, 3 figure
Can majority support save an endangered language? A case study of language attitudes in Guernsey
Many studies of minority language revitalisation focus on the attitudes and perceptions of minorities, but not on those of majority group members. This paper discusses the implications of these issues, and presents research into majority andf minority attitudes towards the endangered indigenous vernacular of Guernsey, Channel Islands. The research used a multi-method approach (questionnaire and interview) to obtain attitudinal data from a representative sample of the population that included politicians and civil servants (209 participants). The findings suggested a shift in language ideology away from the post-second world war âculture of modernisationâ and monolingual ideal, towards recognition of the value of a bi/trilingual linguistic heritage. Public opinion in Guernsey now seems to support the maintenance of the indigenous language variety, which has led to a degree of official support. The paper then discusses to what extent this âattitude shiftâ is reflected in linguistic behaviour and in concrete language planning measures
Meson Exchange Effect on Color Superconductivity
We investigate the effects of pion and gluon exchanges on the formation of
two-flavor color superconductivity at moderate density, . The
chiral quark model proposed by Manohar and Georgi containing pions as well as
gluons is employed to show that the pion exchange reduces substantially the
value of the superconducting gap gotten with the gluon exchange only. It turns
out that the pion exchanges produce a repulsion between quark-quark pair in a
spin and isospin singlet state.
We suggest that the phase consisiting of pions, gluons and quarks is one of
the candidates of in-medium QCD phase at moderate density.Comment: 8 pages, 1 figure, minor correction
Calibration of stochastic computer simulators using likelihood emulation
We calibrate a stochastic computer simulation model of âmoderateâ computational expense. The simulator is an imperfect representation of reality, and we recognise this discrepancy to ensure a reliable calibration. The calibration model combines a Gaussian process emulator of the likelihood surface with importance sampling. Changing the discrepancy specification changes only the importance weights, which lets us investigate sensitivity to different discrepancy specifications at little computational cost. We present a case study of a natural history model that has been used to characterise UK bowel cancer incidence. Data sets and computer code are provided as supplementary material
Quark Number Susceptibility with Finite Chemical Potential in Holographic QCD
We study the quark number susceptibility in holographic QCD with a finite
chemical potential or under an external magnetic field at finite temperature.
We first consider the quark number susceptibility with the chemical potential.
We observe that approaching the critical temperature from high temperature
regime, the quark number susceptibility divided by temperature square develops
a peak as we increase the chemical potential, which confirms recent lattice QCD
results. We discuss this behavior in connection with the existence of the
critical end point in the QCD phase diagram. We also consider the quark number
susceptibility under the external magnetic field. We predict that the quark
number susceptibility exhibits a blow-up behavior at low temperature as we
raise the value of the magnetic field. We finally spell out some limitations of
our study.Comment: 25 pages, 3 figures, published versio
Precision Determination of the Neutron Spin Structure Function g1n
We report on a precision measurement of the neutron spin structure function
using deep inelastic scattering of polarized electrons by polarized
^3He. For the kinematic range 0.014<x<0.7 and 1 (GeV/c)^2< Q^2< 17 (GeV/c)^2,
we obtain at an average . We find relatively large negative
values for at low . The results call into question the usual Regge
theory method for extrapolating to x=0 to find the full neutron integral
, needed for testing quark-parton model and QCD sum rules.Comment: 5 pages, 3 figures To be published in Phys. Rev. Let
Nuclear matter to strange matter transition in holographic QCD
We construct a simple holographic QCD model to study nuclear matter to
strange matter transition. The interaction of dense medium and hadrons is taken
care of by imposing the force balancing condition for stable D4/D6/D6
configuration. By considering the intermediate and light flavor branes
interacting with baryon vertex homogeneously distributed along R^3 space and
requesting the energy minimization, we find that there is a well defined
transition density as a function of current quark mass. We also find that as
density goes up very high, intermediate (or heavy) and light quarks populate
equally as expected from the Pauli principle. In this sense, the effect of the
Pauli principle is realized as dynamics of D-branes.Comment: 13 pages, 14 figure
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