Note on a noncritical holographic model with a magnetic field

Cui, Sheng Liang; Seo, Yunseok; Sin, Sang-Jin; Xu, Wei

doi:10.1103/physrevd.81.066001

Cited by 7 publications

(5 citation statements)

References 47 publications

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“…The QCD-like chiral phase transition, flavor quark transport and parton structure function have been discussed in Refs. [23][24][25][26][27] under this framework. The findings in these references indicate that the thermal phase transition and flavor quark transport under noncritical background is nearly the same as those of the Sakai-Sugimoto model.…”

Section: Noncritical Sakai-sugimoto Modelmentioning

confidence: 98%

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Photoproduction and conductivity in dense holographic QCD

2012

Phys. Rev. D

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We explore the photoemission rate and conductivity in dense QCD by taking the AdS/CFT methods. Specifically, we take three QCD gravity dual models to do comparative studies: D4/D6 model, noncritical Sakai-Sugimoto model and soft-wall AdS/QCD model. We turn on the time component of flavor U(1) gauge field in the bulk side to model the baryon density in QCD. For all three models, we numerically solve the U(1) fluctuation equation to plot the spectral function and photoemission rate for lightlike momenta as well as the AC conductivity. We find that the results for the former two models are very similar to previous studies while the last one show some differences. The conductivity in the soft-wall model seems to be similar to that of holographic superconductor constructed from five-dimensional bulk gravity, i.e. the pseudogap structure. This should be owing to that the infrared (IR) soft-wall (an effective cutoff near the IR of the geometry) produces a mass gap in the dual field theory, which has imprinting in the conductivity as a pseudogap formation. However, the DC conductivity in our computations is finite while it should be a delta peak in holographic superconductor models. Our results show the importance of dilaton running in affecting physical quantities.

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Section: Noncritical Sakai-sugimoto Modelmentioning

confidence: 98%

“…Through Frobenius analysis, we can obtain similar asymptotic behavior for the fluctuation mode a y ðk; u; dÞ as in Eqs. (23) and (24). Our numerical results are stated in the following several figures.…”

Section: Noncritical Sakai-sugimoto Modelmentioning

confidence: 99%

Photoproduction and conductivity in dense holographic QCD

2012

Phys. Rev. D

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“…This parametrization describes a smoothly varyingG which converges slowly to its present value, G N , and is more physical than those based on step functions (e.g. Cui et al 2010). The parameter, a * , denotes the scale-factor of photon decoupling and the parameters µ 0 and a s quantify the deviation ofG from the laboratory measured value, G N , and the scale factor at whichG and G N are equal, respectively.…”

Section: Time Variation Of Newton's Constantmentioning

confidence: 99%

Testing Gravity Using the Growth of Large-Scale Structure in the Universe

Jennings

Baugh

Pascoli

2010

ApJ

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Future galaxy surveys hope to distinguish between the dark energy and modified gravity scenarios for the accelerating expansion of the Universe using the distortion of clustering in redshift space. The aim is to model the form and size of the distortion to infer the rate at which large scale structure grows. We test this hypothesis and assess the performance of current theoretical models for the redshift space distortion using large volume N-body simulations of the gravitational instability process. We simulate competing cosmological models which have identical expansion histories -one is a quintessence dark energy model with a scalar field and the other is a modified gravity model with a time varying gravitational constant -and demonstrate that they do indeed produce different redshift space distortions. This is the first time this approach has been verified using a technique that can follow the growth of structure at the required level of accuracy. Our comparisons show that theoretical models for the redshift space distortion based on linear perturbation theory give a surprisingly poor description of the simulation results. Furthermore, the application of such models can give rise to catastrophic systematic errors leading to incorrect interpretation of the observations. We show that an improved model is able to extract the correct growth rate. Further enhancements to theoretical models of redshift space distortions, calibrated against simulations, are needed to fully exploit the forthcoming high precision clustering measurements.

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“…While including smaller scale observations would appear to improve both FoMs, one has to consider the theoretical uncertainties present in modelling these small scales, especially in the context of modifications to gravity; therefore, it is worthwhile assessing how a conservative approach of neglecting such scales might impact the projected cosmological constraints. Schmidt et al 2009a;Cui, Zhang & Yang 2010;Brax et al 2011;Ferraro, Schmidt & Hu 2011;Zhao, Li & Koyama 2011). In Fig.…”

Section: Surveymentioning

confidence: 99%

Disentangling dark energy and cosmic tests of gravity from weak lensing systematics

Laszlo

Bean

Kirk

et al. 2012

Monthly Notices of the Royal Astronomical Society

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We consider the impact of key astrophysical and measurement systematics on constraints on dark energy and modifications to gravity on cosmic scales. We focus on upcoming photometric ‘stage III’ and ‘stage IV’ large‐scale structure surveys such as the Dark Energy Survey (DES), the Subaru Measurement of Images and Redshifts survey, the Euclid survey, the Large Synoptic Survey Telescope (LSST) and Wide Field Infra‐Red Space Telescope (WFIRST). We illustrate the different redshift dependencies of gravity modifications compared to intrinsic alignments, the main astrophysical systematic. The way in which systematic uncertainties, such as galaxy bias and intrinsic alignments, are modelled can change dark energy equation‐of‐state parameter and modified gravity figures of merit by a factor of 4. The inclusion of cross‐correlations of cosmic shear and galaxy position measurements helps reduce the loss of constraining power from the lensing shear surveys. When forecasts for Planck cosmic microwave background and stage IV surveys are combined, constraints on the dark energy equation‐of‐state parameter and modified gravity model are recovered, relative to those from shear data with no systematic uncertainties, provided fewer than 36 free parameters in total are used to describe the galaxy bias and intrinsic alignment models as a function of scale and redshift. While some uncertainty in the intrinsic alignment (IA) model can be tolerated, it is going to be important to be able to parametrize IAs well in order to realize the full potential of upcoming surveys. To facilitate future investigations, we also provide a fitting function for the matter power spectrum arising from the phenomenological modified gravity model we consider.

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Note on a noncritical holographic model with a magnetic field

Abstract: We consider a noncritical holographic model constructed from an intersecting brane configuration D4/D4-D4 with an external magnetic field. We investigate the influences of this magnetic field on strongly coupled dynamics by the gauge/gravity correspondence.

Cited by 7 publications

References 47 publications

Photoproduction and conductivity in dense holographic QCD

Photoproduction and conductivity in dense holographic QCD

Testing Gravity Using the Growth of Large-Scale Structure in the Universe

Disentangling dark energy and cosmic tests of gravity from weak lensing systematics

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