arXiv subjects

Parijat Dey

Publications and source records attributed to Parijat Dey.

26 records · Page 2Linked to original sources

arXiv2014

Interpolating solution from AdS$_5$ to hyperscaling violating Lifshitz space-time

We construct two interpolating solutions in type II string theory which interpolate between an AdS$_5$ in the UV and a hyperscaling violating three (spatial) dimensional Lifshitz space-time in the IR. The first solution is non-supersymmetric and is obtained from a known intersecting non-supersymmetric D3-brane with chargeless D0-brane solution of type IIB string theory, by restricting some parameters characterizing the solution and going to a new coordinate. In the IR the dilaton is non-constant in general and the metric is three (spatial) dimensional hyperscaling violating Lifshitz with dynamical critical exponent $z=(3+3γ)/(3-γ)$ and hyperscaling violation exponent $θ= 12/(3-γ)$, where $γ$ is a real parameter and can take continuous values from $-1$ to $+1$. At the two extreme values, i.e., for $γ= \pm 1$, the dilaton is constant. The second solution is supersymmetric and is obtained from the known F-D2 bound state solution of type IIA string theory by zooming into a particular region of space. In the UV, the proper description is given in a T-dual frame which is AdS$_5$, whereas in the IR, it gives a three dimensional hyperscaling violating Lifshitz with $z=3$ and $θ=2=d-1$.

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arXiv2013

From AdS to Schrödinger/Lifshitz dual space-times without or with hyperscaling violation

It is observed that the (intersecting) branes of M/string theory, which are known to give AdS geometry (directly or upto a conformal transformation) in the near horizon limit, do also lead to Schr\" odinger/Lifshitz dual space-times (without or with hyperscaling violation) upon using appropriate solution generating transformation and dimensional reduction. We show that the dynamical exponents of the Schr\" odinger and the Lifshitz space-times obtained in this way always add upto 2. We illustrate this by several examples, including M2-, M5-branes of M-theory and D$(p+1)$-branes ($p\neq 4$, since in this case the near horizon limit does not give AdS geometry) of string theory as well as many of their intersecting solutions. The Schr\" odinger space-time can be obtained by the standard wave generating technique along one of the brane directions (for single brane) or one of the common brane directions (for intersecting branes) and then interchanging the light-cone coordinates by double Wick rotations, whereas, the Lifshitz space-time can be obtained by dimensionally reducing (for M-theory) along the wave direction or taking T-duality (for string theory) along the same direction. We thus obtain Schr\" odinger/Lifshitz dual space-times without or with hyperscaling violation from the same M/string theory solutions and they preserve some fraction of the supersymmetry.

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arXiv2013

Zero sound in strange metals with hyperscaling violation from holography

Hyperscaling violating `strange metal' phase of heavy fermion compounds can be described holographically by probe D-branes in the background of a Lifshitz space-time (dynamical exponent $z$ and spatial dimensions $d$) with hyperscaling violation (corresponding exponent $θ$). Without the hyperscaling violation, strange metals are known to exhibit zero sound mode for $z<2$ analogous to the Fermi liquids. In this paper, we study its fate in the presence of hyperscaling violation and find that in this case the zero sound mode exists for $z < 2(1+|θ|/d)$, where the positivity of the specific heat and the null energy condition of the background dictate that $θ<0$ and $z\geq 1$. However, for $z \geq 2(1+|θ|/d)$, there is no well-defined quasiparticle for the zero sound. The systems behave like Fermi liquid for $2|θ|=dz$ and like Bose liquid for $2|θ| = qdz$ (where $q$ is the number of spatial dimensions along which D-branes are extended in the background space), but in general they behave as a new kind of quantum liquid. We also compute the AC conductivity of the systems and briefly comment on the results.

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arXiv2013

Holographic entanglement entropy of the near horizon 1/4 BPS F-D$p$ bound states

It was shown in Dey and Roy (2012) that the near horizon limit of the 1/4 BPS threshold F-D$p$ (for $0\leq p \leq 5$, $p \neq 4$) bound state solutions of type II string theories give rise to space-time metrics endowed with Lifshitz scaling along with hyperscaling violation. Here we compute the holographic entanglement entropy of this system for all $p \neq 4$ (for $p=4$ the space-time has AdS$_2$ structure). For $p=3,5$, we get the expected area law behavior of the entanglement entropy. For $p=0,1$, the entanglement entropy has new area law violations and has the behavior which is in between the linear and logarithmic behaviors. For $p=2$, we get a logarithmic violation of the area law. We also compute the entanglement entropy at finite temperature and show that as the temperature rises, the entanglement entropy makes a crossover to the thermal entropy of the system. We thus obtain the string theoretic realization of holographic EE and various of its aspects noted earlier for generic metric with hyperscaling violation.

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arXiv2013

Lifshitz metric with hyperscaling violation from NS5-Dp states in string theory

In our previous papers we have shown how Lifshitz-like space-time (space-time having a Lifshitz scaling along with a hyperscaling violation) can arise by taking near horizon limits of certain intersecting solutions (F-string with D$p$-branes and also with two D-branes) of string theory. In this paper we construct intersecting bound state solutions in the form of NS5-D$p$-branes (with $1\leq p \leq 6$) of type II string theories. These are 1/4 BPS and threshold bound states unlike the known NS5-D$p$ bound states which are 1/2 BPS and non-threshold. We show that the near horizon limits of these solutions also lead to Lifshitz-like space-time with the dynamical scaling exponent $z=0$ and the hyperscaling violation exponent $θ=9-p$. The spatial dimension of the boundary theory is $d=7-p$. The dilatons in these theories are not constant in general (except for $p=5$) and therefore produce RG flows. So, we also consider the strong coupling phases of these theories and find that these phases also have similar Lifshitz-like structures, except for $p=2$, where it has an AdS$_3$ structure.

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arXiv2012

Intersecting D-branes and Lifshitz-like space-time

In a previous paper (Dey and Roy, arXiv:1203.5381) we have shown how Lifshitz-like space-times (space-times having Lifshitz scaling with hyperscaling violation) arise from 1/4 BPS, threshold F-D$p$ bound state solutions of type II string theories in the near horizon limit. In this paper we show that similar structures also arise from the near horizon limit of 1/4 BPS, threshold intersecting D-brane solutions of type II string theories. Some of these solutions are standard (D$p$-D($p+4$) for $p=0, 2$) and some are non-standard (D$p$-D($p+2)$ for $p = 1, 2, 3$) including D2-D2$'$, D3-D3$'$ and D4-D4$'$ solutions. The dilatons of these solutions in general run (except in D2-D4 and D3-D3$'$ cases) and produce RG flows. We discuss the phase structures of these solutions. D2-D4 and D3-D3$'$ in the near horizon limit do not produce Lifshitz-like space-time, but give AdS$_3$ spaces.

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arXiv2012

Wess-Zumino-Witten Model for Galilean Conformal Algebra

In this note, we construct a Wess-Zumino-Witten model based on the Galilean conformal algebra in 2-spacetime dimensions, which is a nonrelativistic analogue of the relativistic conformal algebra. We obtain exact background corresponding to σ-models in six dimensions (the dimension of the group manifold) and a central charge c=6. We carry out a Sugawara type construction to verify the conformal invariance of the model. Further, we discuss the feasibility of the background obtained as a physical spacetime metric.

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arXiv2012

Lifshitz-like space-time from intersecting branes in string/M theory

We construct 1/4 BPS, threshold F-D$p$ bound states (with $0\leq p \leq 5$) of type II string theories by applying S- and T-dualities to the D1-D5 system of type IIB string theory. These are different from the known 1/2 BPS, non-threshold F-D$p$ bound states. The near horizon limits of these solutions yield Lifshitz-like space-times with varying dynamical critical exponent $z=2(5-p)/(4-p)$, for $p\neq 4$, along with the hyperscaling violation exponent $θ= p - (p-2)/(4-p)$, showing how Lifshitz-like space-time can be obtained from string theory. The dilatons are in general non-constant (except for $p=1$). We discuss the holographic RG flows and the phase structures of these solutions. For $p=4$, we do not get a Lifshitz-like space-time, but the near horizon limit in this case leads to an AdS$_2$ space.

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