Jacobson's Approach Research Articles

Modified gravity theories from the Barrow hypothesis

Barrow proposed that quantum gravity effects might introduce fractal corrections to the area of the event horizon of black holes. The area law gets modified as , with . It was so far unclear whether this assumption could lead to meaningful quantum gravity theories beyond general relativity. In this paper, we argue that this is indeed the case. In particular, assuming Δ to be a radial function, we show that the Barrow hypothesis, together with Jacobson's approach can generate non-trivial modified gravity theories.

More on spacetime thermodynamics in the light of Weyl transformations

It was recently found that, after performing a Weyl conformal transformation, the familiar analogy between black hole mechanics and black hole thermodynamics becomes ambiguous. It was argued that this fact can be traced back to the fundamental dichotomy between matter and geometry, which is at the heart of Einstein's field equations. As a further study of this issue, we investigate here the general link between spacetime thermodynamics and Weyl transformations from two other angles. We first examine the conformal behaviour of the horizon entropy within Wald's approach based on the fundamental diffeomorphism symmetry of $pure$ geometry. We then revisit $-$ using Weyl transformations $-$ Jacobson's derivation of Einstein's field equations, the starting point of which is precisely built on the fundamental dichotomy between matter and geometry. As a result, we show that in order for Jacobson's approach to be able to yield the right Einstein field equations in the conformal frame, a specific conformal behavior of the horizon temperature and its entropy $-$ different from what Wald's approach implies $-$ is required. The two approaches to spacetime thermodynamics become thus incompatible in the conformal frame. In addition, we show $-$ in greater detail in the conformal frame $-$ that in the presence of a null dust the thermodynamics approach for extracting Einstein's field equations necessarily fails. An extensive discussion of the whole issue is given.

Inflationary universe in the presence of a minimal measurable length

In this paper, we will study the effect of having a minimum measurable length on inflationary cosmology. We will analyze the inflationary cosmology in the Jacobson approach. In this approach, gravity is viewed as an emergent thermodynamical phenomena. We will demonstrate that the existence of a minimum measurable length will modify the Friedmann equations in the Jacobson approach. We will use this modified Friedmann equation to analyze the effect of minimum measurable length scale on inflationary cosmology. This analysis will be performed using the Hamiltonian-Jacobi approach. We compare our results to recent data, and find that our model may agree with the recent data.

Non-singular and cyclic universe from the modified GUP

In this paper, we investigate the effects of a new version of the generalized uncertainty principle (modified GUP) on the dynamics of the Universe. As the modified GUP will modify the relation between the entropy and area of the apparent horizon, it will also deform the Friedmann equations within Jacobson's approach. We explicitly find these deformed Friedmann equations governing the modified GUP-corrected dynamics of such a Universe. It is shown that the modified GUP-deformed Jacobson's approach implies an upper bound for the density of such a Universe. The Big Bang singularity can therefore also be avoided using the modified GUP-corrections to horizons' thermodynamics. In fact, we are able to analyze the pre Big Bang state of the Universe. Furthermore, the equations imply that the expansion of the Universe will come to a halt and then will immediately be followed by a contracting phase. When the equations are extrapolated beyond the maximum rate of contraction, a cyclic Universe scenario emerges.

Antiself-dual gravity and supergravity from a pure connection formulation

We consider a pure connection action plus additional algebraic constraints that are suitable for a straightforward supergroup extension. By taking as an internal group [Formula: see text], the action reduces to the Capovilla, Dell and Jacobson approach. By taking as an internal symmetry the supergroup [Formula: see text], and by means of the Bianchi identity and integrability conditions, the equations of motion are those that could be found from antiself-dual supergravity [Formula: see text] with cosmological constant sector.

Utilization of a systemic business process re-engineering method as a tool to improve software process quality

This paper suggests that a ‘software process’ can be viewed as an instance of a ‘business process’. Therefore software process improvement might be achieved by applying the concepts of Business Process Re-engineering (BPR). BPR is introduced and the recent work of Jacobson, using object-oriented concepts to construct a BPR framework, is described. The paper critiques Jacobson's approach as being essentially reductionist, and presents an alternative approach, State-Behaviour Modelling (SBM), that utilizes systems principles in the analysis of problem situations, while generating object models. The application of SMB to model and improve a component of a software development process, is presented.

Assessing the clinical significance of outcome in agoraphobia research: A comparison of two approaches

We evaluated two methods for characterizing clinically significant change in agoraphobia treatment research: The method proposed by Jacobson and colleagues (1991) and an alternative method, in which the endstate functioning of patients (low, medium, or high) was assessed by several criteria relevant for panic disorder with agoraphobia. Whenever possible, statistically determined cutoff points were applied on these criteria. Comparison of the outcome revealed considerable consonance between both methods, although the Jacobson approach was somewhat more lenient in considering patients recovered. The reliable change index, an additional criterion proposed by Jacobson et al. in order to assess whether patients had experienced true change as a result of treatment, had little informational value: All patients who met the criterion of clinically meaningful change had reliably changed as well. Moreover, the reliable change index did not discriminate between patients with medium and low clinical endstatus.