Sharif Digital Repository

The aim of this paper is to investigate the application of solid oxide fuel cell (SOFC) as the prime mover of a combined heat and power (CHP) system. In this paper, four hybrid systems are proposed to improve the performance of CHP and compare with baseline condition. Capacity design and operation strategy of hybrid systems are applied to a case study of a greenhouse located in Mahabad, Iran and optimized by using technical, economic and environmental objective functions. Levelized cost of energy (LCOE) and CO2 emission rate are considered as the objective functions. For LCOE optimization, three scenarios are considered to evaluate the impacts of future energy prices and CO2 tax. In scenario... 

We study holographic entanglement entropy for certain logarithmic conformal field theories by making use of their gravity descriptions. The corresponding gravity descriptions are provided by higher-derivative gravity at critical points where the equations of motion degenerate leading to a log gravity. When a central charge of the dual theory is zero, the entanglement entropy has a new divergent term whose coefficient is given by the "new anomaly" of the logarithmic conformal field theory  

Using the proposal for holographic entanglement entropy in higher derivative gravities, we compute holographic entanglement entropy for the conformal gravity in four dimensions which turns out to be finite. However, if one subtracts the contribution of the four dimensional Gauss-Bonnet term, the corresponding entanglement entropy has a divergent term and indeed restricted to an Einstein solution of the conformal gravity, the resultant entanglement entropy is exactly the same as that in the Einstein gravity. We will also make a comment on the first law of the entanglement thermodynamics for the conformal gravity in four dimensions  

For a given quantum field theory, provided the area of the entangling surface is fixed, what surface maximizes entanglement entropy? We analyze the answer to this question in four and higher dimensions. Surprisingly, in four dimensions the answer is related to a mathematical problem of finding surfaces that minimize the Willmore (bending) energy and eventually to the Willmore conjecture. We propose a generalization of the Willmore energy in higher dimensions and analyze its minimizers in a general class of topologies Sm×Sn and make certain observations and conjectures that may have some mathematical significance  

We have presented a set of laws of entanglement thermodynamics for TT¯-deformed CFTs and in general for T2-deformed field theories. In particular, the first law of this set, states that although we are dealing with a non-trivial deformed theory, the change of the entanglement entropy is simply translated to the change of the bending energy of the entangling surface. We interpret this energy as the energy of decomposition. Probing the whole spectrum of the deformed theory, a second law also results, which suggests an inequality that the first law is derived from its saturation limit. We explain that this second law guarantees the preservation of the unitarity bound. The thermodynamical form... 

We use holographic methods to study the entanglement entropy for excited states in a two dimensional conformal field theory. The entangling area is a single interval and the excitations are produced by in and out vertex operators with given scaling dimensions. On the gravity side we provide the excitations by turning on a scalar field with an appropriate mass. The calculation amounts to using the gravitational background, with a singular boundary, to find the one point function of the vertex operators. The singular boundary is taken care of by introducing a nontrivial UV regulator surface to calculate gravitational partition functions. By means of holographic methods we reproduce the field... 

Abstract: We propose a holographic model for local quench in 1 + 1 dimensional Conformal Field Theory (CFT). The local quench is produced by joining two identical CFT’s on semi-infinite lines. When these theories have a zero boundary entropy, we use the AdS/Boundary CFT proposal to describe this process in terms of bulk physics. Boundaries of the original CFT’s are extended in AdS as dynamical surfaces. In our holographic picture these surfaces detach from the boundary and form a closed folded string which can propagate in the bulk. The dynamics of this string is governed by the tensionless Yo-Yo string solution and its subsequent evolution determines the time dependence after quench. We use... 

In odd dimensions the integrated conformal anomaly is entirely due to the boundary terms [1]. In this paper we present a detailed analysis of the anomaly in five dimensions. We give the complete list of the boundary conformal invariants that exist in five dimensions. Additionally to 8 invariants known before we find a new conformal invariant that contains the derivatives of the extrinsic curvature along the boundary. Then, for a conformal scalar field satisfying either the Dirichlet or the conformal invariant Robin boundary conditions we use the available general results for the heat kernel coefficient a5, compute the conformal anomaly and identify the corresponding values of all boundary... 

In the presence of boundaries, the quantum anomalies acquire additional boundary terms. In odd dimensions, the integrated conformal anomaly, for which the bulk contribution is known to be absent, is nontrivial due to the boundary terms. These terms became a subject of active study in the recent years. In the present paper, we continue our previous study [1,2] and compute explicitly the anomaly for fermions in dimensions d=3, 4 and 5. The calculation in dimension 5 is new. It contains both contributions of the gravitational field and the gauge fields to the anomaly. In dimensions d=3 and 4, we reproduce and clarify the derivation of the results available in the literature. Imposing the... 

We use the holographic methods to calculate the entanglement entropy for field theories modified by TT¯ insertion. Based on the available holographic proposals, this calculation reduces to the holographic computations in AdS with finite cut-off. We perform a direct holographic calculation of the entanglement entropy for two dimensional deformed theory. By direct we mean the evaluation of the gravitational action in the bulk spacetime which has been reconstructed from a dual CFT2 on n-sheeted Riemann surface as a finite cut-off boundary. We also apply Ryu-Takayanagi's prescription to investigate the most general structure of the entanglement entropy for TT¯-deformed theories of arbitrary... 

In this note we address the discrepancy found by Hung, Myers and Smolkin between the holographic calculation of entanglement entropy (using the Jacobson-Myers functional for the holographic minimal surface) and the CFT trace anomaly calculation if one uses the Wald prescription to compute the entropy in six dimensions. As anticipated in our previous work [1] the discrepancy originates entirely from a total derivative term present in the trace anomaly in six dimensions