1,055,690 research outputs found

### The Anisotropic Two-Point Correlation Functions of the Nonlinear Traceless Tidal Field in the Principal-Axis Frame

Galaxies on the largest scales of the Universe are observed to be embedded in
the filamentary cosmic web which is shaped by the nonlinear tidal field. As an
efficient tool to quantitatively describe the statistics of this cosmic web, we
present the anisotropic two-point correlation functions of the nonlinear
traceless tidal field in the principal-axis frame, which are measured using
numerical data from an N-body simulation. We show that both of the nonlinear
density and traceless tidal fields are more strongly correlated along the
directions perpendicular to the eigenvectors associated with the largest
eigenvalues of the local tidal field. The correlation length scale of the
traceless tidal field is found to be ~20 Mpc/h, which is much larger than that
of the density field ~5 Mpc/h. We also provide analytic fitting formulae for
the anisotropic correlation functions of the traceless tidal field, which turn
out to be in excellent agreement with the numerical results. We expect that our
numerical results and analytic formula are useful to disentangle cosmological
information from the filamentary network of the large-scale structures.Comment: ApJ in press, accepted version, minor changes, discussion improve

### Surface r Modes and Burst Oscillations of Neutron Stars

We study the $r$-modes propagating in steadily mass accreting, nuclear
burning, and geometrically thin envelopes on the surface of rotating neutron
stars. For the modal analysis, we construct the envelope models which are fully
radiaitive or have a convective region. As the angular rotation frequency
$\Omega$ is increased, the oscillation frequency $\omega$ of the $r$-modes in
the thin envelopes deviates appreciably from the asymptotic frequency
$\omega=2m\Omega/l^\prime(l^\prime+1)$ defined in the limit of $\Omega\to 0$,
where $\omega$ is the frequency observed in the corotating frame of the star,
and $m$ and $l^\prime$ are the indices of the spherical harmonic function
$Y_{l^\prime}^m$ representing the angular dependence of the modes. We find that
the fundamental $r$-modes in the convective models are destabilized by strong
nuclear burning in the convective region. Because of excessive heating by
nuclear buring, the corotating-frame oscillation frequency $\omega$ of the
$r$-modes in the convective models becomes larger, and hence the inertial-frame
oscillation frequency $|\sigma|$ becomes smaller, than those of the
corresopnding $r$-modes in the radiative models, where $\sigma=\omega-m\Omega$
is negative for the $r$-modes of positive $m$. We find that the relative
frequency change $f=-(\sigma_{conv}-\sigma_{rad})/\sigma_{rad}$ is always
positive and becomes less than $\sim$0.01 for the fundamental $r$-modes of
$l^\prime>|m|+1$ at $|\sigma_{rad}|/2\pi\sim$300Hz for $m=1$ or at
$|\sigma_{rad}|/2\pi\sim$600Hz for $m=2$, where $\sigma_{conv}$ and
$\sigma_{rad}$ denote the oscillation frequencies for the convective and the
radiative envelope models, respectively.Comment: 20 pages, 12 figure

### Spherical gauge fields

We introduce the spherical field formalism for free gauge fields. We discuss
the structure of the spherical Hamiltonian for both general covariant gauge and
radial gauge and point out several new features not present in the scalar field
case. We then use the evolution equations to compute gauge-field and
field-strength correlators

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