108 citations · 1.3k across the 107 of their papers we have counts for
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Emergent diffeomorphism invariance in toy models
Hrvoje Nikolic
Conceptual difficulties in semiclassical and quantum gravity arise from diffeomorphism invariance of classical general relativity. With a motivation to shed some light on these dif…
Submarine paradox softened
Hrvoje Nikolic
In Supplee's submarine paradox, a naive argument based on Lorentz contraction leads to a contradiction that a fast submarine should sink in the water's reference frame but float in…
The trivial solution of the gravitational energy-momentum tensor problem
H. Nikolic
In the literature one often finds the claim that there is no such thing as an energy-momentum tensor for the gravitational field, and consequently, that the total energy-momentum c…
If time is a local observable, then Hawking radiation is unitary
H. Nikolic
In the usual formulation of quantum theory, time is a global classical evolution parameter, not a local quantum observable. On the other hand, both canonical quantum gravity (which…
Time in quantum gravity and black-hole information paradox
H. Nikolic
The fact that canonical quantum gravity does not possess a fundamental notion of time implies that the theory is unitary in a trivial sense. At the fundamental level, this trivial…
The Spacetime View of the Information Paradox
H. Nikolic
In semiclassical gravity, the final state of black-hole evaporation cannot be described by a pure state. Nevertheless, we point out that the system can be described by a generalize…
Resolving the black-hole information paradox by treating time on an equal footing with space
H. Nikolic
Pure states in quantum field theory can be represented by many-fingered block-time wave functions, which treat time on an equal footing with space and make the notions of "time evo…
Quantum black-hole information missing in the semiclassical treatment
H. Nikolic
In the semiclassical treatment of gravity, an external observer can measure only the mean (not the exact) mass of the black hole (BH). By contrast, in fully quantum gravity the exa…
Renormalization of vacuum energy in linearized quantum gravity
H. Nikolic
In linearized quantum gravity, a shift of the average energy-momentum can be compensated by a shift of the average gravitational field. This allows a renormalization scheme that na…
On Cosmological Implications of Gravitational Trace Anomaly
Neven Bilic, Branko Guberina, Raul Horvat +2
We study the infrared effective theory of gravity that stems from the quantum trace anomaly. Quantum fluctuations of the metric induce running of the cosmological constant and the…
Cosmological constant, semiclassical gravity, and foundations of quantum mechanics
H. Nikolic
The old cosmological-constant (CC) problem indicates an inconsistency of the usual formulation of semiclassical gravity. The usual formulation of semiclassical gravity also seems t…
Causal paradoxes: a conflict between relativity and the arrow of time
H. Nikolic
It is often argued that superluminal velocities and nontrivial spacetime topologies, allowed by the theory of relativity, may lead to causal paradoxes. By emphasizing that the noti…
Time in quantum gravity by weakening the Hamiltonian constraint
H. Nikolic
We replace the usual Hamiltonian constraint of quantum gravity H|psi>=0 by a weaker one <psi|H|psi>=0. This allows |psi> to satisfy the time-dependent functional Schrodinger equati…
Proper co-ordinates of non-inertial observers and rotation
H. Nikolic
By proper co-ordinates of non-inertial observers (shortly - proper non-inertial co-ordinates) we understand the proper co-ordinates of an arbitrarily moving local observer. After a…
A general-covariant concept of particles in curved background
H. Nikolic
A local current of particle density for scalar fields in curved background is constructed. The current depends on the choice of a two-point function. There is a choice that leads t…
Inappropriateness of the Rindler quantization
H. Nikolic
It is argued that the Rindler quantization is not a correct approach to study the effects of acceleration on quantum fields. First, the "particle"-detector approach based on the Mi…
Fermi co-ordinates and relativistic effects in non-inertial frames
H. Nikolic
Fermi co-ordinates are proper co-ordinates of a local observer determined by his trajectory in space-time. Two observers at different positions belong to different Fermi frames eve…
Self-gravitating bosons at nonzero temperature
Neven Bilic, Hrvoje Nikolic
A system of charged bosons at finite temperature and chemical potential is studied in a general-relativistic framework. We assume that the boson fields interact only gravitationall…
Notes on covariant quantities in noninertial frames and invariance of radiation in classical and quantum field theory
H. Nikolic
A local observer can measure only the values of fields at the point of his own position. By exploring the coordinate transformation between two Fermi frames, it is shown that two o…
Relativistic contraction and related effects in noninertial frames
H. Nikolic
Although there is no relative motion among different points on a rotating disc, each point belongs to a different noninertial frame. This fact, not recognized in previous approache…
Some remarks on a nongeometrical interpretation of gravity and the flatness problem
H. Nikolic
In a nongeometrical interpretation of gravity, the metric is interpreted as an {\em effective} metric, whereas is interpreted as a fundamen…
The origin of the difference between space and time
Hrvoje Nikolic
All differences between the role of space and time in nature are explained by proposing the principles in which none of the spacetime coordinates has an {\it a priori} special role…