1,336 research outputs found
Topological Mechanics from Supersymmetry
In topological mechanics, the identification of a mechanical system's
rigidity matrix with an electronic tight-binding model allows to infer
topological properties of the mechanical system, such as the occurrence of
`floppy' boundary modes, from the associated electronic band structure. Here we
introduce an approach to systematically construct topological mechanical
systems by an exact supersymmetry (SUSY) that relates the bosonic (mechanical)
and fermionic (e.g. electronic) degrees of freedom. As examples we discuss
mechanical analogues of the Kitaev honeycomb model and of a second-order
topological insulator with floppy corner modes. Our SUSY construction naturally
defines hitherto unexplored topological invariants for bosonic (mechanical)
systems, such as bosonic Wilson loop operators that are formulated in terms of
a SUSY-related fermionic Berry curvature.Comment: 8 pages, 6 figure
First measurement of HI 21cm emission from a GRB host galaxy indicates a post-merger system
We report the detection and mapping of atomic hydrogen in HI 21cm emission
from ESO 184-G82, the host galaxy of the gamma ray burst 980425. This is the
first instance where HI in emission has been detected from a galaxy hosting a
gamma ray burst. ESO 184-G82 is an isolated galaxy and contains a Wolf-Rayet
region close to the location of the gamma ray burst and the associated
supernova, SN 1998bw. This is one of the most luminous HII regions identified
in the local Universe, with a very high inferred density of star formation. The
HI 21cm observations reveal a high HI mass for the galaxy, twice as large as
the stellar mass. The spatial and velocity distribution of the HI 21cm emission
reveals a disturbed rotating gas disk, which suggests that the galaxy has
undergone a recent minor merger that disrupted its rotation. We find that the
Wolf-Rayet region and the gamma ray burst are both located in the highest HI
column density region of the galaxy. We speculate that the merger event has
resulted in shock compression of the gas, triggering extreme star formation
activity, and resulting in the formation of both the Wolf-Rayet region and the
gamma ray burst. The high HI column density environment of the GRB is
consistent with the high HI column densities seen in absorption in the host
galaxies of high redshift gamma ray bursts.Comment: Accepted for publication in MNRAS Letters. 5 pages, 5 figures, 2
tables. For the definitive version visit http://mnrasl.oxfordjournals.org
Evaluation of genetic parameters for agro-metrical characters in carnation genotypes
Carnation (Dianthus caryophyllus) is a worldwide reputed cut-flower crop. The objective of the study was to estimate various genetic parameters like critical difference (CD), phenotypic and genotypic variance, phenotypic and genotypic coefficient of variation (PCV and GCV), broad sense heritability and genetic gain, etc. of Dianthus genotypes in order to assess the magnitude of variability for various agro-metrical characters.The study revealed highly significant differences for all the studied characters, indicating the presence of substantial genetic variability. The phenotypic coefficient of variation(PCV) was higher than its corresponding genotypic counterpart (GCV) for all characters studied. The highest GCV and PCV were evident in total branches per plant; and their lowest values for total number of flowers per plant along with plant height taken at 50% flowering phase. Broad sense heritability ranged from 33.33 (days to seed germination) to 95.30 (plant height at 50% flowering) per cent. Flowers per plant showed low genetic gain; hence, heterosis breeding would be recommended. These characters may serve as effective selection parameter in breeding programme for crop improvement
Experience versus Talent Shapes the Structure of the Web
We use sequential large-scale crawl data to empirically investigate and
validate the dynamics that underlie the evolution of the structure of the web.
We find that the overall structure of the web is defined by an intricate
interplay between experience or entitlement of the pages (as measured by the
number of inbound hyperlinks a page already has), inherent talent or fitness of
the pages (as measured by the likelihood that someone visiting the page would
give a hyperlink to it), and the continual high rates of birth and death of
pages on the web. We find that the web is conservative in judging talent and
the overall fitness distribution is exponential, showing low variability. The
small variance in talent, however, is enough to lead to experience
distributions with high variance: The preferential attachment mechanism
amplifies these small biases and leads to heavy-tailed power-law (PL) inbound
degree distributions over all pages, as well as over pages that are of the same
age. The balancing act between experience and talent on the web allows newly
introduced pages with novel and interesting content to grow quickly and surpass
older pages. In this regard, it is much like what we observe in high-mobility
and meritocratic societies: People with entitlement continue to have access to
the best resources, but there is just enough screening for fitness that allows
for talented winners to emerge and join the ranks of the leaders. Finally, we
show that the fitness estimates have potential practical applications in
ranking query results
Holographic s-wave condensate with non-linear electrodynamics: A nontrivial boundary value problem
In this paper, considering the probe limit, we analytically study the onset
of holographic s-wave condensate in the planar Schwarzschild-AdS background.
Inspired by various low energy features of string theory, in the present work
we replace the conventional Maxwell action by a (non-linear) Born-Infeld (BI)
action which essentially corresponds to the higher derivative corrections of
the gauge fields. Based on a variational method, which is commonly known as the
Sturm-Liouville (SL) eigenvalue problem and considering a non-trivial
asymptotic solution for the scalar field, we compute the critical temperature
for the s-wave condensation. The results thus obtained analytically agree well
with the numerical findings\cite{hs19}. As a next step, we extend our
perturbative technique to compute the order parameter for the condensation.
Interestingly our analytic results are found to be of the same order as the
numerical values obtained earlier.Comment: Minor revision, accepted for publication in Phys. Rev.
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