A new approach is described to help improve the foundations of relativistic viscous fluid dynamics and its coupling general relativity. Focusing on neutral conformal fluids constructed solely in terms hydrodynamic variables, we derive most energy-momentum tensor yielding equations motion second order derivatives, which shown provide a novel type generalization Navier-Stokes for causality holds. We show how this may be derived from kinetic theory. rigorously prove local existence, uniqueness,...

Effective theory arguments are used to derive the most general energy-momentum tensor of a relativistic viscous fluid with an arbitrary equation state (in absence other conserved currents) that is first-order in derivatives energy density and flow velocity does not include extended variables such as Mueller-Israel-Stewart-like theories. This leads causal theory, provided one abandons usual conventions for out-of-equilibrium hydrodynamic put forward by Landau-Lifshitz Eckart. In particular,...

We present the first generalization of Navier-Stokes theory to relativity that satisfies all following properties: (a) system coupled Einstein's equations is causal and strongly hyperbolic; (b) equilibrium states are stable; (c) leading dissipative contributions present, i.e., shear viscosity, bulk thermal conductivity; (d) nonzero baryon number included; (e) entropy production non-negative in regime validity theory; (f) above hold nonlinear without any simplifying symmetry assumptions....

We prove that Einstein's equations coupled to of Israel-Stewart-type, describing the dynamics a relativistic fluid with bulk viscosity and nonzero baryon charge (without shear or diffusion) dynamically gravity, are causal in full nonlinear regime. also show these can be written as first-order symmetric hyperbolic system, implying local existence uniqueness solutions motion. use an arbitrary equation state do not make any simplifying symmetry near-equilibrium assumption, requiring only...

New constraints are found that must necessarily hold for Israel-Stewart-like theories of fluid dynamics to be causal far away from equilibrium. Conditions sufficient ensure causality, local existence, and uniqueness solutions in these also presented. Our results the full nonlinear regime, taking into account bulk shear viscosities (at zero chemical potential), without any simplifying symmetry or near-equilibrium assumptions. findings provide fundamental on magnitude viscous corrections

We prove that ideal chiral hydrodynamics, as derived from kinetic theory, is acausal and its initial-value problem ill posed, both in the linearized case around a local equilibrium solution also full nonlinear regime. Therefore, such theory cannot be used to determine how anomaly affects hydrodynamic evolution. show these fundamental issues can fixed by using different definitions (frames) for fields. This leads causal of hydrodynamics where vorticity strength constrained coefficient encodes anomaly.

We investigate the out-of-equilibrium dynamics of viscous fluids in a spatially flat Friedmann-Lema\^itre-Robertson-Walker cosmology using most general causal and stable energy-momentum tensor defined at first order spacetime derivatives. In this new framework pressureless fluid having density $\rho$ can evolve to an asymptotic future solution which Hubble parameter approaches constant while $\rho \rightarrow 0$, even absence cosmological (i.e., $\Lambda = 0$). Thus, effects model drive...

We derive necessary and sufficient conditions under which a large class of relativistic generalizations Braginskii's magnetohydrodynamics with shear, bulk, heat diffusion effects is causal strongly hyperbolic in the fully nonlinear regime curved spacetime. find that causality severely constrains size nonideal onset kinetic instabilities. Our results are crucial for assessing validity fluid dynamical simulations plasmas near supermassive black holes.

<p style='text-indent:20px;'>We study the theory of relativistic viscous hydrodynamics introduced in [<xref ref-type="bibr" rid="b14">14</xref>, <xref rid="b58">58</xref>], which provided a causal and stable first-order fluids with viscosity case barotropic fluids. The local well-posedness its equations motion has been previously established Gevrey spaces. Here, we improve this result by proving Sobolev spaces.</p>

We present the first generalization of Navier-Stokes theory to relativity that satisfies all following properties: (a) system coupled Einstein's equations is causal and strongly hyperbolic; (b) equilibrium states are stable; (c) leading dissipative contributions present, i.e., shear viscosity, bulk thermal conductivity; (d) non-zero baryon number included; (e) entropy production non-negative in regime validity theory; (f) above holds nonlinear without any simplifying symmetry assumptions....

<p style='text-indent:20px;'>In this manuscript, we study the theory of conformal relativistic viscous hydrodynamics introduced in [<xref ref-type="bibr" rid="b4">4</xref>], which provided a causal and stable first-order fluids with viscosity. Local existence uniqueness solutions to its equations motion have been previously established Gevrey spaces. Here, improve result by proving local Sobolev

We formulate the first-order dissipative anisotropic hydrodynamical theory for a relativistic conformal uncharged fluid, which generalizes Bemfica-Disconzi-Noronha-Kovtun viscous fluid framework. Our approach maintains causal behavior in nonlinear regime with or without general relativity coupling, and we derive analyze constraints on transport coefficients imposed by causality. demonstrate stable of our specific cases, including discussion causality as well stability linearized...

In this work we address the reconstruction problem, investigating construction of field theories from supersymmetric quantum mechanics. The procedure is reviewed, starting reflectionless potentials that admit one and two bound states. We show that, although theory reconstructed potential support a single state unique, it may break unicity in case illustrate with an example, which leads us distinct theories.

The quantum dynamics of nonrelativistic single-particle systems involving noncommutative coordinates, usually referred to as mechanics, has lately been the object several investigations. In this letter we pursue these studies for case multi-particle systems. We use a prototype degenerate electron gas whose is well known in commutative limit. Our central aim here understand qualitatively, rather than quantitatively, main modifications induced by presence coordinates. shall first see that...

In this work we study a modified theory of gravity that contains up to fourth order spatial derivatives as model for the Horava-Lifshitz gravity. The propagator is evaluated and, result, it obtained one extra pole corresponding spin two nonrelativistic massless particle, an term which jeopardizes renormalizability, besides unexpected general relativity unmodified propagator. Then, unitarity proved at tree-level, where has shown have no dynamics, remaining only degrees freedom new pole. Next,...

The classical counterpart of noncommutative quantum mechanics is a constrained system containing only second-class constraints. embedding procedure formulated by Batalin, Fradkin and Tyutin (BFT) enables one to transform this into an Abelian gauge theory exhibiting first class appropriateness the BFT embedding, as implemented in work, verified showing that there exists mapping linking model with invariant sector theory. As known, functional quantization calls for elimination its freedom....

This paper is dedicated to present model independent results for noncommutative quantum mechanics. We determine sufficient conditions the convergence of Born series and, in sequel, unitarity proved full generality.

In this work we report a new result that appears when one investigates the route starts from scalar field theory and ends on supersymmetric quantum mechanics. The subject has been studied before in several distinct ways here unveil an interesting novelty, showing same model may describe mechanical problems.

This is a review paper concerned with the global consistency of quantum dynamics non-commutative systems. Our point departure theory constrained systems, since it provides unified description classical and for models under investigation. We then elaborate on recently reported results sufficient conditions existence Born series unitarity turn, afterwards, into analyzing functional quantization The compatibility between operator approaches established in full generality. intricacies arising...

We prove that ideal chiral hydrodynamics, as derived from kinetic theory, is acausal and its initial-value problem ill-posed both in the linearized case around a local equilibrium solution also full nonlinear regime. Therefore, such theory cannot be used to determine how anomaly affects hydrodynamic evolution. show these fundamental issues can fixed by using different definitions (frames) for fields. This leads causal of hydrodynamics where vorticity strength constrained coefficient encodes anomaly.

The generalized Weyl transform of index $\ensuremath{\alpha}$ is used to implement the time-slice definition phase space path integral yielding Feynman kernel in case noncommutative quantum mechanics. As expected, this representation for not unique but labeled by real parameter $\ensuremath{\alpha}$. We succeed proving that $\ensuremath{\alpha}$-dependent contributions disappear at limit where time slice goes zero. This proof consistency turns out be intricate because Hamiltonian involves...

In this manuscript, we study the theory of conformal relativistic viscous hydrodynamics introduced in arXiv:1708.06255, which provided a causal and stable first-order fluids with viscosity. The local well-posedness its equations motion has been previously established Gevrey spaces. Here, improve result by proving Sobolev