Hydrodynamic excitations from chiral kinetic theory and the hydrodynamic frames

Ghazi

Taghinavaz

et al. 2019

Self Cite

We consider a fluid with weakly broken time and translation symmetries. We assume the fluid also possesses a U (1) symmetry which is not only weakly broken, but is anomalous. We use the second order chiral quasi-hydrodynamics to compute the magneto conductivities of this fluid in the presence of a weak magnetic field. Analogous to the electrical and thermoelectric conductivities, it turns out that the thermal conductivity depends on the coefficient of mixed gauge-gravitational anomaly. Our results can be applied to the hydrodynamic regime of every arbitrary system, once the thermodynamics of that system is known. By applying them to a free system of Weyl fermions at low temperature limit T ≪ µ, we find that our fluid is Onsager reciprocal if the relaxation in all energy, momentum and charge channels occurs at the same rate. In the high temperature limit T ≫ µ, we consider a strongly coupled SU (N c ) gauge theory with N c ≫ 1. Its holographic dual in thermal equilibrium is a magnetized charged brane from which, we compute the thermodynamic quantities and subsequently evaluate the conductivities in gauge theory. On the way, we show that analogous to the weak regime in the system of Weyl fermions, an energy cutoff emerges to regulate the thermodynamic quantities in the strong regime of boundary gauge theory. From this gravity background we also find the coefficients of chiral magnetic effect in agreement with the well-known result of Son-Surowka. * abbasi@ipm.ir † armin.ghazi@physics.

Section: Second Order Hydrodynamics In An Anomalous Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Magneto-transport in an anomalous fluid with weakly broken symmetries, in weak and strong regime

Ghazi

Taghinavaz

et al. 2019

Self Cite

“…In this case with only one single U (1) anomalous currents, one finds five of them including, two sound waves, two chiral Alfvén waves (CAW) together with one chiral magnetic-heat wave (CMHW) [52,53] 12 . In the laboratory frame [55], we find the velocity of these modes as the following: α] . We have used the shorthand notation [α, β] = α 1 β 2 − α 2 β 1 , and similarly we use the same for other commutators.…”

Section: Butterfly Effect and Chiral Transportmentioning

confidence: 99%

“…Firstly, the non-propagation of chiral Alfvén wave in this case shows that this kind of gap-less modes are tight with the presence of gravitational anomaly. If we took λ = 0, we would obtain v CAW = 0, although just in the laboratory frame ( [55,57]). The second point is that in front of every magnetic field factor b, there is an implicit chiral anomaly coefficient C. But since our computations are in the framework of holography, the relation (2.45) has been already imposed and the anomaly coefficient is then not seen explicitly.…”

Section: Butterfly Effect and Chiral Transportmentioning

confidence: 99%

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Quantum chaos, pole-skipping and hydrodynamics in a holographic system with chiral anomaly

Tabatabaei

2020

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It is well-known that chiral anomaly can be macroscopically detected through energy and charge transport, due to chiral magnetic effect. On the other hand, the chaotic modes in a many body system are only associated with energy conservation. So, this suggests that, perhaps, one can detect the microscopic anomalies through the quantum chaos in such systems. To holographically investigate this idea, we consider a magnetized brane in AdS space time with a Chern-Simons coupling in the bulk. By studying the shock wave geometry in this background, we first compute the corresponding butterfly velocities, in the presence of an external magnetic field B, in µ T and B T 2 limit. We find that the butterfly propagation in the direction of B has not the same velocity as the one of opposite direction; the difference is turned out to be as ∆v B = (log(4) − 1)∆v sound with ∆v sound being the difference between velocity of the two sound modes propagating in the system. Such special form of splitting confirms the idea that chiral anomaly can be macroscopically manifested via quantum chaos. We then show that the pole-skipping points of energy density Green's function in the boundary theory coincide precisely with the chaos points. This might be regarded as hydrodynamic origin of quantum chaos in an anomalous system. In addition, by studying the near horizon dynamics of a scalar field on the above background, we find the spectrum of pole-skipping points associated with the two-point function of dual boundary operator. We show that the sum of wavenumbers corresponding to the pole-skipping points at a specific Matsubara frequency follows from a closed formula. Interestingly, we find that the same information about splitting of butterfly velocities is encoded in the pole-skipping points with the lowest Matsubara frequency, independent of scaling dimension of dual boundary operator. * abbasi@lzu.edu.cn † smjty25@gmail.com 4 See also [36] for the first study of pole-skipping at finite coupling. 5 Let us denote that by using symmetries, we only work with a subset of δg µν 's. 6 v is the time coordinate in the Eddington-Finkelstein coordinates.

Magneto-transport in a chiral fluid from kinetic theory

Taghinavaz

Tavakol

2019

Self Cite

We argue that in order to study the magneto-transport in a relativistic Weyl fluid, it is needed to take into account the associated quantum corrections, namely the side-jump effect, at least to second order. To this end, we impose Lorentz invariance to a system of free Weyl fermions in the presence of the magnetic field and find the second order correction to the energy dispersion. By developing a scheme to compute the integrals in the phase space, we show that the mentioned correction has non-trivial effects on the thermodynamics of the system. Specifically, we compute the expression of the negative magnetoresistivity in the system from the enthalpy density in equilibrium. Then in analogy with Weyl semimetal, in the framework of the chiral kinetic theory and under the relaxation time approximation, we explicitly compute the magneto-conductivities, at low temperature limit (T ≪ µ). We show that the conductivities obey a set of Ward identities which follow from the generating functional including the Chern-Simons part. * abbasi@ipm.ir † ftaghinavaz@ipm.ir ‡ omid.