944 research outputs found
On the one-loop correction of "phi^4" theory in higher dimensions
We have considered phi^4 theory in higher dimensions. Using functional
diagrammatic approach, we computed the one-loop correction to effective
potential of the scalar field in five dimensions. It is shown that phi^4 theory
can be regularised in five dimensions. Temperature dependent one-loop
correction and critical temperature T_c are computed and T_c depends on the
fundamental scale M of the theory. A brief discussion of symmetry restoration
is also presented. The nature of phase transitions is examined and is of second
orderComment: 8 pages, 5 figures. To appear in IJMP
Dvali-Gabadadze-Porrati Cosmology in Bianchi I brane
The dynamics of Dvali-Gabadadze-Porrati Cosmology (DGP) braneworld with an
anisotropic brane is studied. The Friedmann equations and their solutions are
obtained for two branches of anisotropic DGP model. The late time behavior in
DGP cosmology is examined in the presence of anisotropy which shows that
universe enters a self-accelerating phase much later compared to the isotropic
case. The acceleration conditions and slow-roll conditions for inflation are
obtained
Bulk scalar field in DGP braneworld cosmology
We investigated the effects of bulk scalar field in the braneworld
cosmological scenario. The Friedmann equations and acceleration condition in
presence of the bulk scalar field for a zero tension brane and cosmological
constant are studied. In DGP model the effective Einstein equation on the brane
is obtained with bulk scalar field. The rescaled bulk scalar field on the brane
in the DGP model behaves as an effective four dimensional field, thus standard
type cosmology is recovered. In present study of the DGP model, the late-time
accelerating phase of the universe can be explained .Comment: 10 pages, to appear in JCA
New approach to time domain classification of broadband noise in gravitational wave data
Transient broadband noise in gravitational wave (GW) detectors-also known as noise triggers (referred to as triggers for brevity)-can often be a deterrant to the efficiency with which astrophysical search pipelines detect sources. It is important to understand their instrumental or environmental origin so that they could be eliminated or accounted for in the data. Since the number of triggers is large, data mining approaches such as clustering and classification are useful tools for this task. Classification of triggers based on a handful of discrete properties has been done in the past. A rich information content is available in the waveform or \ shape\ of the triggers that has had a rather restricted exploration so far. This paper presents a new way to classify triggers deriving information from both trigger waveforms as well as their discrete physical properties, using a sequential combination of the longest common subsequence (LCSS) and LCSS coupled with Fast Time Series Evaluation (FTSE) for waveform classification, and the multidimensional hierarchical classification (MHC) analysis for the grouping based on physical properties. A generalized k-means algorithm is used with the LCSS (and LCSS+FTSE) for clustering the triggers using a validity measure to determine the correct number of clusters in absence of any prior knowledge. The results have been demonstrated by simulations and by application to a segment of real LIGO data from the sixth science run. © 2012 American Physical Society
A New Approach to Time Domain Classification of Broadband Noise in Gravitational Wave Data
Broadband noise in gravitational wave (GW) detectors, also known as triggers,
can often be a deterrant to the efficiency with which astrophysical search
pipelines detect sources. It is important to understand their instrumental or
environmental origin so that they could be eliminated or accounted for in the
data. Since the number of triggers is large, data mining approaches such as
clustering and classification are useful tools for this task. Classification of
triggers based on a handful of discrete properties has been done in the past. A
rich information content is available in the waveform or 'shape' of the
triggers that has had a rather restricted exploration so far. This paper
presents a new way to classify triggers deriving information from both trigger
waveforms as well as their discrete physical properties using a sequential
combination of the Longest Common Sub-Sequence (LCSS) and LCSS coupled with
Fast Time Series Evaluation (FTSE) for waveform classification and the
multidimensional hierarchical classification (MHC) analysis for the grouping
based on physical properties. A generalized k-means algorithm is used with the
LCSS (and LCSS+FTSE) for clustering the triggers using a validity measure to
determine the correct number of clusters in absence of any prior knowledge. The
results have been demonstrated by simulations and by application to a segment
of real LIGO data from the sixth science run.Comment: 16 pages, 16 figure
Automatic Extraction and Sign Determination of Respiratory Signal in Real-time Cardiac Magnetic Resonance imaging
In real-time (RT) cardiac cine imaging, a stack of 2D slices is collected
sequentially under free-breathing conditions. A complete heartbeat from each
slice is then used for cardiac function quantification. The inter-slice
respiratory mismatch can compromise accurate quantification of cardiac
function. Methods based on principal components analysis (PCA) have been
proposed to extract the respiratory signal from RT cardiac cine, but these
methods cannot resolve the inter-slice sign ambiguity of the respiratory
signal. In this work, we propose a fully automatic sign correction procedure
based on the similarity of neighboring slices and correlation to the
center-of-mass curve. The proposed method is evaluated in eleven volunteers,
with ten slices per volunteer. The motion in a manually selected
region-of-interest (ROI) is used as a reference. The results show that the
extracted respiratory signal has a high, positive correlation with the
reference in all cases. The qualitative assessment of images also shows that
the proposed approach can accurately identify heartbeats, one from each slice,
belonging to the same respiratory phase. This approach can improve cardiac
function quantification for RT cine without manual intervention.Comment: IEEE ISBI 2020, International Symposium on Biomedical Imagin
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