اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدTopology of quantum vacuum
71
0
0.0
(
0
)
تأليف
G. E. Volovik
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Topology in momentum space is the main characteristics of the ground states of a system at zero temperature, the quantum vacua. The gaplessness of fermions in bulk, on the surface or inside the vortex core is protected by topology. Irrespective of the deformation of the parameters of the microscopic theory, the energy spectrum of these fermions remains strictly gapless. This solves the main hierarchy problem in particle physics. The quantum vacuum of Standard Model is one of the representatives of topological matter alongside with topological superfluids and superconductors, topological insulators and semi-metals, etc. There is a number of of topological invariants in momentum space of different dimensions. They determine universality classes of the topological matter and the type of the effective theory which emerges at low energy, give rise to emergent symmetries, including the effective Lorentz invariance, and emergent gauge and gravitational fields. The topological invariants in extended momentum and coordinate space determine the bulk-surface and bulk-vortex correspondence, connecting the topology in bulk with the real space. The momentum space topology gives some lessons for quantum gravity. In effective gravity emerging at low energy, the collective variables are the tetrad field and spin connections, while the metric is the composite object of tetrad field. This suggests that the Einstein-Cartan-Sciama-Kibble theory with torsion field is more relevant. There are also several scenarios of Lorentz invariance violation governed by topology, including splitting of Fermi point and development of the Dirac points with quadratic and cubic spectrum. The latter leads to the natural emergence of the Horava-Lifshitz gravity.
قيم البحث
اقرأ أيضاً
The ability to generate particles from the quantum vacuum is one of the most profound consequences of Heisenbergs uncertainty principle. Although the significance of vacuum fluctuations can be seen throughout physics, the experimental realization of
vacuum amplification effects has until now been limited to a few cases. Superconducting circuit devices, driven by the goal to achieve a viable quantum computer, have been used in the experimental demonstration of the dynamical Casimir effect, and may soon be able to realize the elusive verification of analogue Hawking radiation. This article describes several mechanisms for generating photons from the quantum vacuum and emphasizes their connection to the well-known parametric amplifier from quantum optics. Discussed in detail is the possible realization of each mechanism, or its analogue, in superconducting circuit systems. The ability to selectively engineer these circuit devices highlights the relationship between the various amplification mechanisms.
We propose a simplified protocol of quantum energy teleportation (QET) for holographic conformal field theory (CFT) in 3-dimensional anti-de Sitter space with or without black hole. As a tentative proposal, we simplify the standard QET by replacing A
lices local measurement with the local projection, which excites the system from ground state into a particular state dual to a Banados geometry. We then mimic Bobs local operation of the usual QET for extracting energy by deforming the UV surface with a local bump. Adopting the surface/state duality this deformation corresponds to local unitary. We evaluate the extraction of energy from the holographic stress tensor, and find that Bob always gains energy extraction in our protocol. This could be related to the positive energy theorem of the dual gravity. Moreover, the ratio of extraction energy to injection one is a universal function of the UV surface deformation profile.
We study in detail various information theoretic quantities with the intent of distinguishing between different charged sectors in fractionalized states of large-$N$ gauge theories. For concreteness, we focus on a simple holographic $(2+1)$-dimension
al strongly coupled electron fluid whose charged states organize themselves into fractionalized and coherent patterns at sufficiently low temperatures. However, we expect that our results are quite generic and applicable to a wide range of systems, including non-holographic. The probes we consider include the entanglement entropy, mutual information, entanglement of purification and the butterfly velocity. The latter turns out to be particularly useful, given the universal connection between momentum and charge diffusion in the vicinity of a black hole horizon. The RT surfaces used to compute the above quantities, though, are largely insensitive to the electric flux in the bulk. To address this deficiency, we propose a generalized entanglement functional that is motivated through the Iyer-Wald formalism, applied to a gravity theory coupled to a $U(1)$ gauge field. We argue that this functional gives rise to a coarse grained measure of entanglement in the boundary theory which is obtained by tracing over (part) of the fractionalized and cohesive charge degrees of freedom. Based on the above, we construct a candidate for an entropic $c$-function that accounts for the existence of bulk charges. We explore some of its general properties and their significance, and discuss how it can be used to efficiently account for charged degrees of freedom across different energy scales.
We analyze properties of unstable vacuum states from the point of view of the quantum theory. In the literature one can find some suggestions that some of false (unstable) vacuum states may survive up to times when their survival probability has a no
n-exponential form. At asymptotically late times the survival probability as a function of time $t$ has an inverse power--like form. We show that at this time region the energy of the false vacuum states tends to the energy of the true vacuum state as $1/t^{2}$ for $t to infty$. This means that the energy density in the unstable vacuum state should have analogous properties and hence the cosmological constant $Lambda = Lambda (t)$ too. The conclusion is that $Lambda$ in the Universe with the unstable vacuum should have a form of the sum of the bare cosmological constant and of the term of a type $1/t^{2}$: $Lambda(t) equiv Lambda_{bare} + d/ t^{2}$ (where $Lambda_{bare}$ is the cosmological constant for the Universe with the true vacuum).
In quantum theory the vacuum is defined as a state of minimum energy that is devoid of particles but still not completely empty. It is perhaps more surprising that its definition depends on the geometry of the system and on the trajectory of an obser
ver through space-time. Along these lines we investigate the case of an atom flying at constant velocity near a planar surface. Using general concepts of statistical mechanics it is shown that the motion-modified interaction with the electromagnetic vacuum is formally equivalent to the interaction with a thermal field having an effective temperature determined by the atoms velocity and distance from the surface. This result suggests new ways to experimentally investigate the properties of the quantum vacuum in non-equilibrium systems and effects such as quantum friction.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
