5,563 research outputs found
Blowup Equations for 6d SCFTs. I
We propose novel functional equations for the BPS partition functions of 6d
(1,0) SCFTs, which can be regarded as an elliptic version of
Gottsche-Nakajima-Yoshioka's K-theoretic blowup equations. From the viewpoint
of geometric engineering, these are the generalized blowup equations for
refined topological strings on certain local elliptic Calabi-Yau threefolds. We
derive recursion formulas for elliptic genera of self-dual strings on the
tensor branch from these functional equations and in this way obtain a
universal approach for determining refined BPS invariants. As examples, we
study in detail the minimal 6d SCFTs with SU(3) and SO(8) gauge symmetry. In
companion papers, we will study the elliptic blowup equations for all other
non-Higgsable clusters.Comment: 52 pages, 3 figure
Compact Visibility Representation of Plane Graphs
The visibility representation (VR for short) is a classical representation of plane graphs. It has various applications and has been extensively studied. A main focus of the study is to minimize the size of the VR. It is known that there exists a plane graph with vertices where any VR of requires a grid of size at least (2/3)n x((4/3)n-3) (width x height). For upper bounds, it is known that every plane graph has a VR with grid size at most (2/3)n x (2n-5), and a VR with grid size at most (n-1) x (4/3)n. It has been an open problem to find a VR with both height and width simultaneously bounded away from the trivial upper bounds (namely with size at most c_h n x c_w n with c_h < 1 and c_w < 2st$-orientation and a good dual s^*t^*-orientation at the same time, and thus is far more challenging. Since st-orientation is a very useful concept in other applications, this result may be of independent interests
Revisiting the distance, environment and supernova properties of SNR G57.2+0.8 that hosts SGR 1935+2154
We have performed a multi-wavelength study of supernova remnant (SNR)
G57.2+0.8 and its environment. The SNR hosts the magnetar SGR 1935+2154, which
emitted an extremely bright ms-duration radio burst on 2020 Apr 28 (The
Chime/Frb Collaboration et al. 2020; Bochenek et al. 2020). We used the 12CO
and 13CO J=1-0 data from the Milky Way Image Scroll Painting (MWISP) CO line
survey to search for molecular gas associated with G57.2+0.8, in order to
constrain the physical parameters (e.g., the distance) of the SNR and its
magnetar. We report that SNR G57.2+0.8 is likely impacting the molecular clouds
(MCs) at the local standard of rest (LSR) velocity V_{LSR} ~ 30 km/s and
excites a weak 1720 MHz OH maser with a peak flux density of 47 mJy/beam. The
chance coincidence of a random OH spot falling in the SNR is <12%, and the
OH-CO correspondence chance is 7% at the maser spot. This combines to give < 1%
false probability of the OH maser, suggesting a real maser detection. The LSR
velocity of the MCs places the SNR and magnetar at a kinematic distance of
d=6.6 +/- 0.7 kpc. The nondetection of thermal X-ray emission from the SNR and
the relatively dense environment suggests G57.2+0.8 be an evolved SNR with an
age (d/6.6 kpc) yr. The explosion energy of G57.2+0.8 is
lower than erg,
which is not very energetic even assuming a high ambient density = 10
cm. This reinforces the opinion that magnetars do not necessarily result
from very energetic supernova explosions.Comment: 9 pages, 5 figures, accepted for publication in the Astrophysical
Journa
The linearized second law for any higher curvature gravity with the scalar and the electromagnetic fields
The first law of black hole thermodynamics is suitable for any diffeomorphism
invariant gravity, and the entropy in the first law is the Wald entropy which
is highly dependent on the non-minimal coupling interactions in the theory of
gravity. However, whether the Wald entropy still satisfies the second law needs
to be investigated. The entropy of black holes obeying the linearized second
law in arbitrary high-order curvature gravity is given, which can be written as
the Wald entropy with correction terms. It indicates that the Wald entropy is
not commonly obeying the linearized second law for any high-order curvature
gravity. When the interactions of gravity with matter fields are included in
the theory of gravity, the entropy of black holes obeying the linearized second
law has not been obtained in this case. Considering any high-order curvature
gravity with the scalar and the electromagnetic fields, from the Raychaudhuri
equation, the entropy obeying the linearized second law is generally obtained,
which can be expressed as the Wald entropy with correction terms as well. The
entropy does not include the contribution from the electromagnetic fields, and
the correction terms contain the contribution from the minimal coupling
interaction between gravity and the scalar fields. Since the entropy satisfying
the linearized second law depends only on the non-minimal coupling interaction
of gravity in previous research, this result upends our understanding of the
entropy of black holes obeying the linearized second law in any gravitational
theory with matter fields.Comment: 17 page
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