Mordred

It is a consideration that shouldn't be ignored. Granted where is no or little risk due to distance etc. I would agree but one also must be able to guarantee that the entirety of the asteroid has zero potential of entering our atmosphere once the detonations contaminate the asteroid.

Understood however using nukes is one of the three main researched options the others being high impact devices and gravity tractors.

Here this will help. This paper discusses the application of nuclear devices vs asteroids https://ntrs.nasa.gov/api/citations/20205008370/downloads/Nuclear_Devices_for_Planetary_Defense_ASCEND_2020_FINAL_2020-10-02.pdf The idea is feasible but has its own realm of problems. The paper mentions a few of them including political issues.

It seems your confusion is thinking the FLRW metric for flat spacetime only includes the 3d portion for spatial components. It also includes the time component for 4d spacetime. However for flat spacetime you don't require the Gamma correction between coordinate time and proper time. It's literally no different Than GR for flat spacetime or Euclidean geometry the only difference is the commoving coordinates which is equated via the scale factor "a". The FLRW metric is literally a GR solution.

While not directly a populizer the physicist that got me hooked was Allen Guth with his original False Vacuum inflationary model. I spent the first few years of my studies chasing the process of virtual particle production including many processes you don't hear about today including Parker radiation that was applied to universe expansion. ( that version never went far however Parker radiation now applies to MRI's).

As mentioned its useful for quick references. However one has to be careful on reliability. More often than not you would find good textbooks, dissertation papers and peer review material far more reliable. This is particularly true with subjects that are often seen in our Speculation forum such as ether based theories as one example. I've often seen wiki pages edited to support a particular view point. Thankfully those pages typically don't last long before they get changed again.

Mainly depends on several factors though such as the solar wind poynting vectors, distance and asteroid composition. The hard truth though is no single method works for every possible scenario. Your best off having a range of possible solutions.

You can also use multiple gravity tractors without risk of nuclear fallout.

Might surprise someone but it also is used in string theory.

It does both quite well. Without requiring specific circumstances or distances. That is something that is a major advantage of any theory. If your theory requires specific speeds or distances to show something it usually indicates the idea is lacking. More often than not amounting to numerology. The Lorentz transforms works extremely well in both SR and GR.

You know you really should use the transformations for Lorentz. They are easy to use and work regardless of velocity of the signals. Others have already mentioned that

If you don't need high end graphics, a lot of storage space or a good quality camera on your phone. Then there is nothing wrong with a cheap phone for just phone and text. I use one for work purposes and keep my high end phone for everyday home use.

I doubt that's justification for new particles outside the standard model considering what we do know in regard to electrowesk symmetry breaking occurring less than a second after the BB. So far too much handwriting is in this thread that has little to do with anything physics related.

Yes but the better ones are not cheap however here is a couple of affordable models https://radio-astronomy.org/node/248#:~:text=Beginners usually purchase one of,cost less than %24200 each. Some of the above are kits which seems to be more common to build your own rather than purchase one.

Interesting paper thanks for sharing.

That would explain the essay style.

that makes little sense, we describe our universe with standard model of particles why would you think the initial conditions wouldn't apply the same standard model of particles we see in our present ? (other than particle generations)

Why do I feel this has been copied and pasted ? If so then you need to include the reference source. Not that the OP has ever responded. I don't know if your still seeking answer to these excellent questions but this article describes local vs global symmetries as well as the connections specifically the gauge connections which you have above for \(A_\mu \) https://www.physics.rutgers.edu/grad/618/lects/localsym_2.pdf @KJW Your math savvy enough that the article should answer your questions but if not let me know and I should be able to help if not then this article will also help. Particularly since it includes how local, global, global internal and gauge symmetries are defined mathematically and includes the localized constraint.

Cosmological Principle implies \[d\tau^2=g_{\mu\nu}dx^\mu dx^\nu=dt^2-a^2t{\frac{dr^2}{1-kr^2}+r^2d\theta^2+r^2\sin^2\theta d\varphi^2}\] the Freidmann equations read \[(\frac{\dot{a}}{a})^2+\frac{k}{a^2}=\frac{8\pi G}{3}\rho\] for \[\rho=\sum^i\rho_i=\rho_m+\rho_{rad}+\rho_\Lambda\] \[2\frac{\ddot{a}}{a}+(\frac{\dot{a}}{a})^2+\frac{k}{a^2}=-8\pi Gp\] for \[p=\sum^ip_i=P_{rad}+p_\Lambda\] with conservation of the energy momentum stress tensor \[T^{\mu\nu}_\nu=0\] \[\dot{p}a^3=\frac{d}{dt}[a^3(\rho+p)]\Rightarrow \frac{d}{dt}(\rho a^3)=-p\frac{d}{dt}a^3\] \[p=\omega\rho\] given w=0 \(\rho\propto a^{-3}\) for matter, radiation P=1/3 \(\rho\propto{-3}\), Lambda w=-1.\(p=-\rho\) for k=0 \[H_o^2=\frac{k}a^2_O=\frac{8\pi G}{3}(\rho^0+\rho_{rad}^0\\rho_\Lambda)\] dividing by \(H^2_0\) and \(P^0_{crit}=\frac{3H^2_0}{8\pi G}\) gives \[1=-\frac{k}{h_0^2a^2_0}+\Omega^o_m+\Omega^0_{rad}=\Omega^0_\Lambda\] \[\Omega_k^0=-\frac{k}{h^2_0a^2_0}\Rightarrow 1=\Omega_k^0+\Omega^0_{rad}+\Omega^0_\Lambda\] densities can be written as \[\rho_{rad}=\rho^0_{rad}(\frac{a_o}{a})^4=\frac{3}{8\pi G}H_0^2\Omega^0_{rad}(\frac{a_o}{a})^4\] \[\Omega_m=\rho^0_m(\frac{a_o}{a})^3=\frac{3}{8\pi G}H_0^2\Omega^0_{rad}(\frac{a_o}{a})^3\] \[\rho_\Lambda=\rho_\Lambda^0=\frac{3}{8\pi G}H_o^2\Omega^0_\Lambda\] \[-\frac{k}{a^2}=\overbrace{-\frac{k}{a^2_0H_o^2}}^{\Omega^0_k}H^2_0(\frac{a_o}{a})^2\] with \(1+z=\frac{a_0}{a}\) densities according to scale factor as functions of redshift. \[\rho_{rad}=\frac{3}{8\pi g}H^2_o\Omega^0_{rad}(\frac{a_o}{a}^4=\frac{3}{8\pi G}H^2_0\Omega^0_{rad}(1+z)^4\] \[\rho_m=\frac{3}{8\pi g}H^2_o\Omega^0_m(\frac{a_o}{a}^3=\frac{3}{8\pi G}H^2_0\Omega^0_m(1+z)^3\] \[\rho_\Lambda=\frac{3}{8\pi G}H_0^2\Omega^0_\Lambda\] \[H^2=H_o^2[\Omega^2_{rad}(1+z)^4+\Omega_m^0(1+z)^3+\Omega_k^0(1+z)^2+\Omega_\Lambda^0]\] the Hubble parameter can be written as \[H=\frac{d}{dt}ln(\frac{a(t)}{a_0}=\frac{d}{dt}ln(\frac{1}{1+z})=\frac{-1}{1+z}\frac{dz}{dt}\] look back time given as \[t=\int^{t(a)}_0\frac{d\acute{a}}{\acute{\dot{a}}}\] \[\frac{dt}{dz}=H_0^{-1}\frac{-1}{1+z}\frac{1}{[\Omega_{rad}(1+z^4)+\Omega^0_m(1=z0^3+\Omega^0_k(1+z)^2+\Omega_\Lambda^0]^{1/2}}\] \[t_0-t=h_1\int^z_0\frac{\acute{dz}}{(1+\acute{z})[\Omega^0_{rad}(1+\acute{z})^4+\Omega^0_m(1+\acute{z})^3=\Omega^0_k(1+\acute{z})^2+\Omega^0_\Lambda]^{1/2}}\]

No that's not what I'm stating. The time reversal for anti particles results from the negative frequency modes. It doesn't mean the antiparticle travels back in time. That particular model suggested it did. One detail though electroweak symmetry breaking isn't really about CPT. That's more relation to baryogenesis and leptogenesis. Electroweak symmetry breaking describes when particles acquire mass and lose symmetry with other particles aka drops out of thermo equilibrium. This corresponds to the relevant force couplings. Strong, weak and EM force couplings. ( yes this includes Higgs Dirac and Yukawa couplings of the SM model). There's two very similar named processes that can get confused (Electroweak Baryogenesis) and (electroweak phase transition). The latter is the thermal equilibrium dropout. The former is suggested to occur during the EWPT (electroweak phase transition) happens. The (EWBG) electroweak baryogenesis is where the CPT relations are involved. Leptogenesis would occur just prior to EWBG. Once again involves CPT.

Yes it's plausible the model I just mentioned had the same BB origin point. Matter and forward time in one universe. Antimatter and reverse time in the other universe. Both resulting from the same BB event. However as stated that model essentially died though you do come across attempts to renew the model. Here is a brief description of the model https://physicsworld.com/a/our-universe-has-antimatter-partner-on-the-other-side-of-the-big-bang-say-physicists/

Rather meaningless to describe time as diluting. How one measures time is observer dependant. However you do not get time dilation due to expansion.

There was an older multiverse model that has matter in one universe with antimatter and time reversal in the other universe. It long ago fell out of any research interest. ( due to better understanding of anti-matter in that the time reversal is a mathematical treatment for symmetry purposes and not actuality)

Good but it's still useful to understand how the NFW profile deals with Kepler curve. Now a little hint there is a means for a matter only universe to expand though it's related to gravity it isn't how it's described so far in this thread. Gravity only attracts it never repels. Matter also exerts no pressure term. So it isn't due to pressure.

Once again simply applying Newtons gravitational laws will tell you differently. The only way to avoid Kepler curve for rotation is to surround the galaxy with a fairly uniform mass density that is greater than the baryonic matter distribution. Aka dark matter via the NFW profile. We can also detect our motion and compensate this is called dipole anistropy it's actually why the first Planck dataset had the axis of evil. They didn't have the needed calibration for our peculiar motion.